Then he found a way to package it and other DNA-repair enzymes inside tiny spherical pockets of phospholipids called liposomes.
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The membranes that enclose the cells of all living things here on Earth are made of phospholipids, molecules with long, non-polar (water-repelling) "tails" and polar (water-loving) heads.
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If you remember high school biology, you'll know that phospholipids form a bi-layer, with the water-loving parts on the outside, and the water-repelling bits on the inside.
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Then there are intralipids, an emulsion of soybean oil, egg phospholipids and glycerin administered intravenously and described as a way to decrease natural killer cell activation in the immune system and ostensibly aid in embryo implantation.
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According to Dr. Whitney, the Aphrodisiac IV is a Myer's cocktail that includes minerals (magnesium, calcium, zinc, selenium, and B vitamins), phospholipids, and glutathione, as well as an injection of adrenal cortex extract and eleutherococcus (Siberian ginseng).
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Image Credit: James Stevenson"What makes vinyl cyanide potentially useful molecule for this is that it's amphiphilic—it has a polar and a non polar end," just like our membranes' phospholipids, Maureen Palmer, a recent graduate of St. Olaf College and lead author on the new study, explained.
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In healthy cells, an ATP (adenosine triphosphate)-dependent enzyme removes negatively charged phospholipids such as phosphatidyl serine from the outer leaflet of the cell membrane. An apoptotic cell (that is, one undergoing apoptosis) no longer actively manages the distribution of phospholipids in its outer membrane and hence begins to display negatively charged phospholipids on its exterior surface. These negatively charged phospholipids are recognized by phagocytes such as macrophages. Protein S binds to the negatively charged phospholipids and functions as a bridge between the apoptotic cell and the phagocyte.
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Lysophosphatidylcholine accounts for 4.6% of phospholipids found in coconut oil, which make up 0.2% of lipids in coconut oil. This is compared to vegetable oils, which may contain 2-3% phospholipids.
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Phospholipids are important natural surfactant lipids Anti-asthmatic combinations comprising surface active phospholipids used in enhancing penetration and bioavailability.PHOSPHOLIPID-BASED INHALATION SYSTEM Phospholipids act by reducing the high surface tension forces at the air-water interface within the alveoli, thereby reducing the pressure needed to expand the lungs, Thus, commercially available formulations of phospholipids have been designed to spread rapidly over an air-aqueous interface, thereby reducing what is otherwise a very high surface tension of water.
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There are two types of ether lipids, plasmanyl- and plasmenyl-phospholipids. Plasmanyl-phospholipids have an ether bond in position sn-1 to an alkyl group. Plasmenyl-phospholipids have an ether bond in position sn-1 to an alkenyl group, 1-0-alk-1’-enyl-2-acyl-sn-glycerol (AAG). The latter type is called plasmalogens.
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PLA1 hydrolyzes nonionic substrates preferentially over ionic substrates. Optimum pH conditions for PLA1 activity on neutral phospholipids is around 7.5, whereas the optimal conditions for PLA1 activity on acidic phospholipids is around 4.
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To make carbon nanotubes soluble in water, phospholipids such as lysoglycerophospholipids have been used. The single phospholipid tail wraps around the carbon nanotube, but the double tailed phospholipids did not have the same ability.
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A disadvantage to this technique is that it is limited to phospholipids.
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Example of an ethanolamine plasmalogen with the characteristic vinyl ether linkage at the sn-1 position and an ester linkage at the sn-2 position Plasmalogens are a subclass of ether phospholipids that are commonly found in cell membranes in the nervous, immune and cardiovascular systems. There are two types of ether phospholipids, plasmanyl and plasmenyl. Plasmenyl- phospholipids, which include plasmalogen, and have an ether bond in position SN1 to an alkenyl group. Plasmanyl-phospholipids, in distinction, have an ether bond in position SN1 to an alkyl group.
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Some hemolysins damage the erythrocyte membrane by cleaving the phospholipids in the membrane.
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The main compounds that S. sucromutans must obtain from such ruminal fluid are phospholipids. It is even able to thrive without a ruminal fluid supplement if provided with phospholipids and fatty acids via a preparation such as 60% pure phosphatidylcholine.
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Although most C2 domains interact with the membrane (phospholipids) in a Ca2+-dependent manner, some C2 domains can interact with the membrane without binding to Ca2+. Similarly, C2 domains have been evolved to have different specificities for lipids. Many C2 domains such as synaptotagmin C2A, bind to anionic phospholipids (PS or PIP2 containing phospholipids). However, other C2 domains such as cPLA2-α C2 domain bind to zwitterionic lipids (e.g. PC).
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Vaccination was associated with significant reductions in total cholesterol, free cholesterol, phospholipids, and triglycerides.
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Choline is transformed to different phospholipids, like phosphatidylcholines and sphingomyelins. These are found in all cell membranes and from the membranes of most cell organelles. Phosphatidylcholines are structurally important part of the cell membranes. In humans 40–50% of their phospholipids are phosphatidylcholines.
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Phospholipid-derived fatty acids (PLFAs) are widely used in microbial ecology as chemotaxonomic markers of bacteria and other organisms. Phospholipids are the primary lipids composing cellular membranes. Phospholipids can be saponified, which releases the fatty acids contained in their diglyceride tail. Once the phospholipids of an unknown sample are saponified, the composition of the resulting PLFA can be compared to the PLFA of known organisms to determine the identity of the sample organism.
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The lipid component of MFGM is rich in phospholipids, glycosphingolipids, and cholesterol. Phospholipids make up approximately 30% of the total lipid weight of MFGM, the three most prominent being sphingomyelin (SM), phosphatidylcholine (PC), and phosphatidylethanolamine (PE), which together represent up to 85% of total phospholipids. Phospholipids and sphingolipids play central roles in cerebral neurogenesis and migration during fetal development, as well as promoting neuronal growth, differentiation, and synaptogenesis during the first year of life. Other important polar lipids present in the membrane include the glycerophospholipids phosphatidylserine (PS) and phosphatidylinositol (PI), as well as gangliosides (GG), which are sphingolipids containing sialic acid and an oligosaccharide side chain.
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The movement of phospholipids, even those located in the outer leaflet of the membrane, is regulated by the actin-based membrane skeleton meshwork. Which is surprising, because the membrane skeleton is located on the cytoplasmic surface of the plasma membrane, and cannot directly interact with the phospholipids located in the outer leaflet of the plasma membrane. To explain the hop diffusion of phospholipids, consistently with that of TM proteins, a model named “anchored TM-protein picket model” has been proposed. In this model various TM proteins are anchored to and aligned along the membrane skeleton, and effectively act as rows of pickets against the free diffusion of phospholipids.
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The brain preferentially uses choline to synthesize acetylcholine. This limits the amount of choline available to synthesize phosphatidylcholine. When the availability of choline is low or the need for acetylcholine increases, phospholipids containing choline can be catabolized from neuronal membranes. These phospholipids include sphingomyelin and phosphatidylcholine.
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Phosphatidic acids are anionic phospholipids important to cell signaling and direct activation of lipid-gated ion channels. Hydrolysis of phosphatidic acid gives rise to one molecule each of glycerol and phosphoric acid and two molecules of fatty acids. They constitute about 0.25% of phospholipids in the bilayer.
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Chemical structure of Dinogunellins A-D. These poisonous toxins from fish roe are unusual phospholipids containing adenosine and 2-aminosuccinamide. Modified from Matsunaga et al, 2009. Dinogunellins are unusual toxic phospholipids found in the roe of some fishes, and is one of the best studied ichthyotoxin.
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Like phospholipids, these fatty acid derivatives have a polar head and nonpolar tails. Unlike phospholipids, sphingolipids have a sphingosine backbone. Sphingolipids exist in eukaryotic cells and are particularly abundant in the central nervous system. For example, sphingomyelin is part of the myelin sheath of nerve fibers.
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Cholesterol has the ability to eliminate the liquid to solid phase transition in phospholipids. Due to sphingomyelin transition temperature being within physiological temperature ranges, cholesterol can play a significant role in the phase of sphingomyelin. Sphingomyelin are also more prone to intermolecular hydrogen bonding than other phospholipids.
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Examples of the major membrane phospholipids and glycolipids: phosphatidylcholine (PtdCho), phosphatidylethanolamine (PtdEtn), phosphatidylinositol (PtdIns), phosphatidylserine (PtdSer).The cell membrane consists of three classes of amphipathic lipids: phospholipids, glycolipids, and sterols. The amount of each depends upon the type of cell, but in the majority of cases phospholipids are the most abundant, often contributing for over 50% of all lipids in plasma membranes. Glycolipids only account for a minute amount of about 2% and sterols make up the rest.
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Attachment of a cation to causes the complex to cross the bilipidic layer undergoing a flip- flop. The headgroup aligns itself with the phospholipids of the inner sheet and the fatty acid chain interacts with the phospholipids acyl chains. The cation is then delivered into the intracellular medium.
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DSC monitoring can occur at slow rates which is a disadvantage in monitoring fast phase transitions within phospholipids.
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These compounds are unsaturated fatty acids, although they are rarely found in natural lipids (fats, waxes, phospholipids, etc.).
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Choline is stored in the cell membranes and organelles as phospholipids, and inside cells as phosphatidylcholines and glycerophosphocholines.
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The phosphate group can be modified with simple organic molecules such as choline, ethanolamine or serine. Phospholipids are a key component of all cell membranes. They can form lipid bilayers because of their amphiphilic characteristic. In eukaryotes, cell membranes also contain another class of lipid, sterol, interspersed among the phospholipids.
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Lecithins are present in all living organisms. An egg yolk has a high concentration of lecthins- which are commercially important as an emulsifying agent in products such as mayonnaise. Lecithins are also present in brain and nerve tissue. ;Other phospholipids There are many other phospholipids, some of which are glycolipids.
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Chemically, phosphatidylethanols are phospholipids carrying two fatty acid chains, which are variable in structure, and one phosphate ethyl ester.
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Computational simulations of phospholipids are often performed using molecular dynamics with force fields such as GROMOS, CHARMM, or AMBER.
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Commercial lecithin, as used by food manufacturers, is a mixture of phospholipids in oil. The lecithin can be obtained by water degumming the extracted oil of seeds. It is a mixture of various phospholipids, and the composition depends on the origin of the lecithin. A major source of lecithin is soybean oil.
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After a cell has entered apoptosis, the negatively charged phospholipids are transported to the outer cell surface by a hypothetical protein known as scramblase. Phagocytic white blood cells express a receptor that can bind to and detect the negatively charged phospholipids on the apoptotic cell surfaces. After detection the apoptotic cells are removed.
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P4 ATPases (or Type IV ATPases) are flippases involved in the transport of phospholipids, such as phosphatidylserine, phosphatidylcholine and phosphatidylethanolamine.
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These serve fish and mammals as food. The furan fatty acids thus absorbed are incorporated into phospholipids and cholesterol esters.
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Thromboplastin is the combination of both phospholipids and tissue factor, both of which are needed in the activation of the extrinsic pathway. However, partial thromboplastin is just phospholipids, and not tissue factor. Currently, recombinant tissue factor is available and used in some PT assays. Placental derivatives are still available and are used in some laboratories.
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The research also suggests that ethanol enhances the association between cholesterol-phospholipids within the liquid-ordered bilayers. The mechanism on how ethanol induces the liquid- disorder phase as well as enhances the cholesterol-phospholipid association is still not understood. The researchers have mentioned that part of the liquid- disorder formation occurs possibly be interrupting the hydrophobic region of the phospholipids, by binding closely towards the hydrophilic region of the phospholipid, and acting as "filler" since ethanol cannot closely align with the neighboring phospholipids. All of these possible mechanisms can be contributed to ethanol's amphiphilic nature.
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Apoptosis is a form of programmed cell death that is used by the body to remove unwanted, damaged, or senescent cells from tissues. Removal of apoptotic cells is carried out via phagocytosis by white blood cells such as macrophages and dendritic cells. Phagocytic white blood cells recognize apoptotic cells by their exposure of negatively charged phospholipids (phosphatidylserine) on the cell surface. In normal cells, the negative phospholipids reside on the inner side of the cellular membrane while the outer surface of the membrane is occupied by uncharged phospholipids.
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While lipid tails primarily modulate bilayer phase behavior, it is the headgroup that determines the bilayer surface chemistry. Most natural bilayers are composed primarily of phospholipids, but sphingolipids and sterols such as cholesterol are also important components. Of the phospholipids, the most common headgroup is phosphatidylcholine (PC), accounting for about half the phospholipids in most mammalian cells. PC is a zwitterionic headgroup, as it has a negative charge on the phosphate group and a positive charge on the amine but, because these local charges balance, no net charge.
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These phospholipids could be found as a complex with non-toxic proteins like in the cabezon toxin or in the lipostichaerin.
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Phospholipids or some detergents aid the transfer of thiocyanatoiron into chlorinated solvents like chloroform and can be determined in this fashion.
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Overall, the PX domain main function is to target SNX8 mainly to early endosomes and other membranes rich in phosphatidylinositol 3-phosphate phospholipids.
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One way hemolysin lyses erythrocytes is by forming pores in phospholipid bilayers. Other hemolysins lyse erythrocytes by hydrolyzing the phospholipids in the bilayer.
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Like most unsaturated fatty acids, the 9-HODEs formed in cells are incorporated into cellular phospholipids principally at the sn-2 position of the phospholipid (see Phospholipase A2);Exp Dermatol. 1993 Feb;2(1):38-4J Lipid Res. 1993 Sep;34(9):1473-82 since, however, the linoleic acid bound to cellular phospholipids is susceptible to non-enzymatic peroxidation and free- radical attack,Free Radic Biol Med. 1995 Jun;18(6):1003-12Biochim Biophys Acta. 1999 May 18;1438(2):204-12 the 9-HODEs in cellular phospholipids may also derive more directly from in-situ oxidation.
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The phosphatase domain in VSPs is highly homologous to the tumor suppressor PTEN, and acts to remove phosphate groups from phospholipids in the membrane containing the VSP. Phospholipids such as inositol phosphates are signaling molecules which exert different effects depending on the pattern in which they are phosphorylated and dephosphorylated. Therefore, the action of VSPs is to indirectly regulate processes dependent on phospholipids. The main substrate that has been characterized so far for VSPs (including hVSP1 but not hVSP2/TPTE, which shows no phosphatase activity) is phosphatidylinositol (4,5)-bisphosphate, which VSPs dephosphorylate at the 5' position.
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To modify the performance of lecithin to make it suitable for the product to which it is added, it may be hydrolysed enzymatically. In hydrolysed lecithins, a portion of the phospholipids have one fatty acid removed by phospholipase. Such phospholipids are called lysophospholipids. The most commonly used phospholipase is phospholipase A2, which removes the fatty acid at the C2 position of glycerol.
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As polypeptides intended to be membrane proteins grow from the ribosomes, they are inserted into the ER membrane itself and are kept there by their hydrophobic portions. The rough ER also produces its own membrane phospholipids; enzymes built into the ER membrane assemble phospholipids. The ER membrane expands and can be transferred by transport vesicles to other components of the endomembrane system.
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Choline phospholipids also form lipid rafts in the cell membranes along with cholesterol. The rafts are centers, for example for receptors and receptor signal transduction enzymes. Phosphatidylcholines are needed for the synthesis of VLDLs: 70–95% of their phospholipids are phosphatidylcholines in humans. Choline is also needed for the synthesis of pulmonary surfactant, which is a mixture consisting mostly of phosphatidylcholines.
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Half of the membrane mass in human and most mammalian red blood cells are proteins. The other half are lipids, namely phospholipids and cholesterol.
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Unlike Class A and B GPCRs, phospholipids bind within the transmembrane bundles and allosteric modulators bind at the interface of GABAB1 and GABAB2 subunits.
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The outer leaflet of cancer cell membranes appears to be enriched with negatively charged phospholipids, which seems to explain the antitumor properties of ribotoxins.
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Phospholipids containing abnormal fatty acids are also less easily eliminated and so are retained in the plasma and increase the coagulability of blood, thereby contributing to coronary and cerebral thrombosis. The deficiency of normal phospholipids in the epidermis and gut makes their structure faulty and so may contribute to seborrhoeic eczema and peptic ulcer. Similarly, deficiency of normal phospholipids or the presence of abnormal phospholipids in the nervous system leads to defective structure, including demyelination, which would cause multiple sclerosis and possibly mental illness. Deficiency of EFAs may increase susceptibility to X-ray and chemical carcinogens, the former in conjunction with the latter leading to leukaemia and the latter to carcinoma of the bronchus and to the predominance of carcinoma of the stomach in males, the male requirement for EFAs being about five times that of the female.
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Choline is a precursor for the synthesis of phospholipids. When a cell is about to divide, it synthesizes these phospholipids to generate enough material to build the cell membranes of the two daughter cells. Thus it was hypothesized that highly proliferative tumors would uptake more choline than the surrounding healthy tissue. This was first tested in brain tumors after successful demonstration of choline uptake in the brain.
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Lecithins may also be modified by a process called fractionation. During this process, lecithin is mixed with an alcohol, usually ethanol. Some phospholipids, such as phosphatidylcholine, have good solubility in ethanol, whereas most other phospholipids do not dissolve well in ethanol. The ethanol is separated from the lecithin sludge, after which the ethanol is removed by evaporation to obtain a phosphatidylcholine-enriched lecithin fraction.
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Phospholipid synthesis occurs in the cytosolic side of ER membrane that is studded with proteins that act in synthesis (GPAT and LPAAT acyl transferases, phosphatase and choline phosphotransferase) and allocation (flippase and floppase). Eventually a vesicle will bud off from the ER containing phospholipids destined for the cytoplasmic cellular membrane on its exterior leaflet and phospholipids destined for the exoplasmic cellular membrane on its inner leaflet.
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Diffuse hazy opacity of the right cornea in a patient with Tangier disease. Tangier disease results in familial high-density lipoprotein deficiency. High-density lipoproteins are created when a protein in the bloodstream, Apolipoprotein A1 (apoA1), combines with cholesterol and phospholipids. The cholesterol and phospholipids used to form HDL originate from inside cells but are transported out of the cell into the blood via the ABCA1 transporter.
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Platelet activation causes its membrane surface to become negatively charged. One of the signaling pathways turns on scramblase, which moves negatively charged phospholipids from the inner to the outer platelet membrane surface. These phospholipids then bind the tenase and prothrombinase complexes, two of the sites of interplay between platelets and the coagulation cascade. Calcium ions are essential for the binding of these coagulation factors.
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The basic premise is that as individual organisms (especially bacteria and fungi) die, phospholipids are rapidly degraded and the remaining phospholipid content of the sample is assumed to be from living organisms. As the phospholipids of different groups of bacteria and fungi contain a variety of somewhat unusual fatty acids, they can serve as useful biomarkers for such groups. PLFA profiles and composition can be determined by purifying the phospholipids and then cleaving the fatty acids for further analysis. Knowledge of the composition and metabolic activity of the microbiota in soils, water and waste materials is useful in optimizing crop production, in bioremediation and in understanding microbial ecosystems.
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In contrast, in phospholipids (polar lipids), Nile red has an excitation maximum of about 554 nm (green), and an emission maximum of about 638 nm (red).
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It is involved in macrophage, cholesterol and phospholipids transport, and may regulate cellular lipid homeostasis in other cell types. Several alternative splice variants have been identified.
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These calcifications are an indication of previous microscopic cell injury, occurring in areas of cell necrosis when activated phosphatases bind calcium ions to phospholipids in the membrane.
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The cPLA2s act specifically on phospholipids that contain AA, EPA or GPLA at their SN2 position. cPLA2 may also release the lysophospholipid that becomes platelet-activating factor.
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Lipids are a broad category of mid-sized molecules that are hydrophobic or amphipathic. In surfactant, two subcategories of lipids are relevant: phospholipids and sterols. Sterols are represented by cholesterol, which has an important role in the overall structure and motion of the lipids as a whole, but is vastly outnumbered by the phospholipids in surfactant. DPPC (dipalmitoylphosphatidylcholine), as mentioned above, is a lipid with very useful stabilizing and compacting attributes.
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Phospholipids can act as emulsifiers, enabling oils to form a colloid with water. Phospholipids are one of the components of lecithin which is found in egg-yolks, as well as being extracted from soybeans, and is used as a food additive in many products, and can be purchased as a dietary supplement. Lysolecithins are typically used for water-oil emulsions like margarine, due to their higher HLB ratio.
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Scramblases, flippases, and floppases are three different types of enzymatic groups of phospholipid transportation enzymes. The inner-leaflet, facing the inside of the cell, contains negatively charged amino-phospholipids and phosphatidylethanolamine. The outer-leaflet, facing the outside environment, contains phosphatidylcholine and sphingomyelin. Scramblase is an enzyme, present in the cell membrane, that can transport (scramble) the negatively charged phospholipids from the inner-leaflet to the outer-leaflet, and vice versa.
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The activity of this protein is sensitive to phospholipids. This gene was originally known as ARFGAP1, but that is now the name of a related but different gene.
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Fatty acid chains are found in two major components of membrane lipids: phospholipids and sphingolipids. A third major membrane component, cholesterol, does not contain these fatty acid units.
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However, when Quillaia saponins, cholesterol and phospholipids are mixed under the specific stoichiometry that forms ISCOMs, this haemolytic activity is practically eliminated, while the adjuvant activity is retained.
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Other alcohols, such as cetyl alcohol (predominant in spermaceti), may replace glycerol. In the phospholipids, one of the fatty acids is replaced by phosphoric acid or a monoester thereof.
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P2 ATPases (or Type II ATPases) are split into four groups. Topological type II ATPases (specific for Na+,K+, H+ Ca2+, Mg2+ and phospholipids) predominate in eukaryotes (approx. twofold).
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In molecular biology, the choline/ethanolamine kinase family includes choline kinase() and ethanolamine kinase (). Ethanolamine and choline are major membrane phospholipids, in the form of glycerophosphoethanolamine and glycerophosphocholine. Ethanolamine is also a component of the glycosylphosphatidylinositol (GPI) anchor, which is necessary for cell-surface protein attachment. The de novo synthesis of these phospholipids begins with the creation of phosphoethanolamine and phosphocholine by ethanolamine and choline kinases in the first step of the CDP-ethanolamine pathway.
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Because of the EU requirement to declare additions of allergens in foods, in addition to regulations regarding genetically modified crops, a gradual shift to other sources of lecithin (such as sunflower lecithin) is taking place. The main phospholipids in lecithin from soy and sunflower are phosphatidyl choline, phosphatidyl inositol, phosphatidyl ethanolamine, phosphatidylserine, and phosphatidic acid. They often are abbreviated to PC, PI, PE, PS and PA, respectively. Purified phospholipids are produced by companies commercially.
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Schematic drawing of the steps followed during vesosome synthesis. Vesosome multicompartment structure encapsulates unilamellar liposomes within a second bilayer. For this purpose, it is necessary to form bilayers that can be opened and closed at will, without disrupting the inner content. This is achieved by adding ethanol to a variety of saturated phospholipids in the gel phase, which drives interdigitation of phospholipids bilayers and subsequent fusion of small vesicles to form flat bilayer sheets.
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Phospholipase A1 encoded by the PLA1A gene is a phospholipase enzyme which removes the 1-acyl. Phospholipase A1 is an enzyme that resides in a class of enzymes called phospholipase that hydrolyze phospholipids into fatty acids. There are 4 classes, which are separated by the type of reaction they catalyze. In particular, phospholipase A1 (PLA1) specifically catalyzes the cleavage at the SN-1 position of phospholipids, forming a fatty acid and a lysophospholipid.
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There are no simple methods available for analysis of phospholipids since the close range of polarity between different phospholipid species makes detection difficult. Oil chemists often use spectroscopy to determine total Phosphorus abundance and then calculate approximate mass of phospholipids based on molecular weight of expected fatty acid species. Modern lipid profiling employs more absolute methods of analysis, with nuclear magnetic resonance spectroscopy (NMR spectroscopy), particularly 31P-NMR, while HPLC-ELSD provides relative values.
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Phosphatidylethanolamines are found in all living cells, composing 25% of all phospholipids. In human physiology, they are found particularly in nervous tissue such as the white matter of brain, nerves, neural tissue, and in spinal cord, where they make up 45% of all phospholipids. Phosphatidylethanolamines play a role in membrane fusion and in disassembly of the contractile ring during cytokinesis in cell division. Additionally, it is thought that phosphatidylethanolamine regulates membrane curvature.
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Legionella lytica is a Gram-negative bacterium from the genus Legionella.UniProtResearch Letter Cellular envelope phospholipids from Legionella lytica Marta Palusinska-Szysz, Rafal Kalitynski, Ryszard Russa, Andrzej L. Dawidowicz & Wincenty J.
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The slugs and other snails are researched and have been found to have a high count of fatty acid composition of phospholipids, including omega 6 and other important fatty acids.
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Commercial egg lecithin, specified in the United States National Formulatory (USP/NF) as used by pharmaceutical companies, is a highly purified mixture of phospholipids, devoid of triglycerides, cholesterol, or proteins.
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Phospholipids are commonly found in the phospholipid bilayer of membranes. They have hydrophilic heads and hydrophopic tails. A protein is another type of macromolecules. Amino acids are the monomers of proteins.
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VAV Life Sciences Private Limited is an Indian trading company dealing with healthcare ingredients including lecithin and phospholipids, with products having application in the nutrition, pharmaceuticals, cosmetics and drug delivery markets.
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These ribotoxin bonds are responsible for recognition of both the negatively charged acid phospholipids that facilitate their entry into cells, and the ribosome- specific features that allow them to cause inactivation.
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Early studies by Hiroshi Nikaido in 1962 suggest a direct relationship between the amount of beta-galactoside permease activity in a cell and the turnover rate of phospholipids in E. coli. In his experiments with gram-positive and gram- negative bacterial cells under varying conditions, the level of P32 in phospholipids was found to be increased under conditions of maximal activity in beta-galactoside permease. Insofar, Nikaido concluded that this correlation suggested that phospholipids are involved in the process of transporting beta- galactosides through the cell membrane. However, later research in 1965 by Alvin Tarlov and Eugene Kennedy using carbon tracers reveals increased levels of glycerol and serine, in addition to those of phosphorus, in the presence of increasing levels of beta-galactoside accumulation.
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Each milliliter of poractant alfa contains 80 mg of surfactant (extract) that includes 76 mg of phospholipids and 1 mg of protein of which 0.2 mg is surfactant protein B (SP-B). Depending on local country registration, CUROSURF is available in 1.5mL vials, 3.0mL vials, and/or twin packs containing two 1.5mL vials. The amount of phospholipids is calculated from the content of phosphorus and contains 55 mg of phosphotidylcholine of which 30 mg is dipalmitoylphosphatidylcholine.
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Rearrangements of glycosphingolipids, phospholipids, as well as cholesterol explains changes in membrane fluidity. Some studies developed at the Regional Center for Biotechnology at Haryana (India) have revealed that free hydroxyl groups on specific bile phospholipids increase solvent dipole penetration within the membrane. The number and order of these functional groups are tightly bound. Studies using mice have been of particular importance in sensing other biomolecules which influence glycerol and acyl chain regions of the plasma membrane.
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In eucaryotic cells, new phospholipids are manufactured by enzymes bound to the part of the endoplasmic reticulum membrane that faces the cytosol. These enzymes, which use free fatty acids as substrates, deposit all newly made phospholipids into the cytosolic half of the bilayer. To enable the membrane as a whole to grow evenly, half of the new phospholipid molecules then have to be transferred to the opposite monolayer. This transfer is catalyzed by enzymes called flippases.
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Prokaryotes are divided into two different groups, Archaea and Bacteria, with bacteria dividing further into gram-positive and gram-negative. Gram-negative bacteria have both a plasma membrane and an outer membrane separated by periplasm, however, other prokaryotes have only a plasma membrane. These two membranes differ in many aspects. The outer membrane of the gram-negative bacteria differ from other prokaryotes due to phospholipids forming the exterior of the bilayer, and lipoproteins and phospholipids forming the interior.
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Antibodies against phosphatidylserine and phosphatidylethanolamine are against the trophoblast. These phospholipids are essential in the aiding the cells of the fetus to remain attached to the cells of the uterus with implantation. If a female has antibodies against these phospholipids, they will be destroyed through the immune response and ultimately the fetus will not be able to remain bound to the uterus. These antibodies also jeopardize the health of the uterus by altering the blood flow to the uterus.
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Phospholipids can occur in many biological classes (such as in plant roots, fungi, as well as in soil bacteria), so care has to be taken in over-assigning PLFA biomarkers to the wrong class. Even though phospholipids occur in many different life forms, the fatty acid side chains between differing life forms can be quite unique. Polyunsaturated fatty acids (e.g. 18:3 ω3c) are found in plants, algae and cyanobacteria, but are often not present in bacteria.
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Droplet Interface Bilayers (DIBs) are phospholipid-encased droplets that form bilayers when they are put into contact. The droplets are surrounded by oil and phospholipids are dispersed in either the water or oil. As a result, the phospholipids spontaneously form a monolayer at each of the oil-water interfaces. DIBs can be formed to create tissue-like material with the ability to form asymmetric bilayers, reconstitute proteins and protein channels or made for use in studying electrophysiology.
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Fatty acids are usually produced industrially by the hydrolysis of triglycerides, with the removal of glycerol (see oleochemicals). Phospholipids represent another source. Some fatty acids are produced synthetically by hydrocarboxylation of alkenes.
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A saponifiable lipid is one with an ester functional group, that can be hydrolyzed under basic conditions. These include phospholipids, glycolipids, sphingolipids, and the waxes. These lipids are known as complex lipids.
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These techniques enable detection of phospholipids, sphingolipids and glycerolipids in tissues such as heart, kidney and brain. Furthermore, distribution of many different lipid molecular species often define anatomical regions within these tissues.
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This location indicates that under normal conditions the substrate and the active site are physically separated, since in E. coli phospholipids are exclusively located in the inner leaflet of the outer membrane.
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Pentenoic acids are technically mono-unsaturated fatty acids, although they are rare or unknown in biological lipids (fats, waxes, phospholipids, etc.). A salt or ester of such an acid is called a pentenoate.
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Dipalmitoylphosphatidylcholine (DPPC) is routinely used to formulate some medicines used for treatment of respiratory distress syndrome (RDS) in newborns. Current synthetic surfactants are combinations of DPPC along with other phospholipids, neutral lipids and lipoproteins. The treatment of preterm infants with RDS using surfactants was initially developed in the 1960s, and recent studies have demonstrated an improvement in clinical outcomes. The first treatment given to some newborns with RDS was surfactant phospholipids, specifically DPPC, by means of an aerosol (Robillard, 1964).
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Aqueous solutions of manganese(II) chloride are used in 31P-NMR to determine the size and lamellarity of phospholipid vesicles. When manganese chloride is added to a vesicular solution, Mn2+ paramagnetic ions are released, perturbing the relaxation time of the phospholipids' phosphate groups and broadening the resulting 31P resonance signal. Only phospholipids located in the outermost monolayer exposed to Mn2+ experience this broadening. The effect is negligible for multilamellar vesicles, but for large unilamellar vesicles, a ~50% reduction in signal intensity is observed.
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Phospholipases A2 (PLA2s) are enzymes that cleave fatty acid in position two of phospholipids, hydrolyzing the bond between the second fatty acid “tail” and the glycerol molecule. This particular phospholipase specifically recognizes the sn-2 acyl bond of phospholipids and catalytically hydrolyzes the bond, releasing arachidonic acid and lysophosphatidic acid. Upon downstream modification by cyclooxygenases or lipoxygenases, arachidonic acid is modified into active compounds called eicosanoids. Eicosanoids include prostaglandins and leukotrienes, which are categorized as anti-inflammatory and inflammatory mediators.
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Prostaglandins are derived from the cell membrane phospholipids through a series of enzymatic reactions. Phospholipase A2 cleaves arachidonic acid from membrane phospholipids and is eventually converted to prostaglandins by cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). Due to this mechanism, prostaglandins have a presence in many areas of the body and allow for diverse physiological and pathological functions. Primarily known for its role in mediating inflammation: pain, swelling, redness, and warmth, prostaglandin synthesis is a target for many drugs.
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The core region consists of an alpha helical disk. The convex side of this disk has type 2 calcium-binding sites. They are important for allowing interaction with the phospholipids at the plasma membrane.
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The function of this protein has not yet been determined; however, it may involve transport of phospholipids from liver hepatocytes into bile. Alternative splicing of this gene results in several products of undetermined function.
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Several variations on this basic structure exist, including backbones such as sphingosine in the sphingomyelin, and hydrophilic groups such as phosphate as in phospholipids. Steroids such as sterol are another major class of lipids.
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A 3D model of ethanol, a volatile, flammable, colorless liquid and a straight- chain alcohol with the molecular formula of C2H5OH. The presence of ethanol can lead to the formations of non-lamellar phases also known as non-bilayer phases. Ethanol has been recognized as being an excellent solvent in an aqueous solution for inducing non-lamellar phases in phospholipids. The formation of non-lamellar phases in phospholipids is not completely understood, but it is significant that this amphiphilic molecule is capable of doing so.
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Degumming is the first step in the refining process to remove phospholipids, gums, waxes and other impurities from the crude oil. The oil is treated with water or dilute acids such as phosphoric acid, which exploits the fact that the phospholipids are attracted to water because of their amphipathic nature, and turns the lipids into hydrated gums. These gums are insoluble in oil and are then separated from the oil using centrifuges. The separated gums are then dried and manufactured into emulsifying agents such as lecithin.
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Ideally, sphingomyelin molecules are shaped like a cylinder, however many molecules of sphingomyelin have a significant chain mismatch (the lengths of the two hydrophobic chains are significantly different). The hydrophobic chains of sphingomyelin tend to be much more saturated than other phospholipids. The main transition phase temperature of sphingomyelins is also higher compared to the phase transition temperature of similar phospholipids, near 37 C. This can introduce lateral heterogeneity in the membrane, generating domains in the membrane bilayer. Sphingomyelin undergoes significant interactions with cholesterol.
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The cation-carrier effect is characterized by surfactin's ability to drive monovalent and divalent cations through an organic barrier. The two acidic residues aspartate and glutamate form a "claw" of sorts which easily stabilizes divalent cations. Calcium ions make for the best-fitting cations stabilizing the surfactin conformation and functioning as an assembly template for the formation of micelles. When surfactin penetrates the outer sheet, its fatty acid chain interacts with the acyl chains of the phospholipids, with its headgroup in proximity to the phospholipids polar heads.
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Scheme of a liposome formed by phospholipids in an aqueous solution. Liposomes are composite structures made of phospholipids and may contain small amounts of other molecules. Though liposomes can vary in size from low micrometer range to tens of micrometers, unilamellar liposomes, as pictured here, are typically in the lower size range with various targeting ligands attached to their surface allowing for their surface-attachment and accumulation in pathological areas for treatment of disease. A liposome is a spherical vesicle having at least one lipid bilayer.
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The PLA2G6 gene encodes for a phospholipase A2 enzyme, which is a subclass of enzyme that catalyzes the release of fatty acids from phospholipids. This type of enzyme is responsible for breaking down (metabolizing) phospholipids. Phospholipid metabolism is essential for many body processes, including helping to maintain the integrity of the cell membrane. Specifically, the A2 phospholipase produced from the PLA2G6 gene, sometimes called PLA2 group VI, helps to regulate the levels of a compound called phosphatidylcholine, which is abundant in the cell membrane.
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A second approach would be to discourage the oxidation of LDL, thereby breaking the inflammatory cycle. Lipoproteins consist of a packaging of triglycerides and esterfied cholesterol within a monolayer shell consisting of phospholipids and a class of proteins called apolipoproteins. The phospholipids are amphipathic, consisting of a hydrophobic tail which faces inwards, binding with the triglycerides and cholesterol, and a hydrophilic head which faces outwards, making the lipoproteins water-soluble. Polyunsaturated fatty acids (PUFA) contained in the outer shell make the lipoproteins especially susceptible to oxidation.
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Molecular Cell Biology. 5th ed. W.H. Freeman and Company New York, 2004. 535–539. The phospholipid bilayer is a two-layer structure mainly composed of phospholipids, which are amphiphilic molecules that have hydrophilic and hydrophobic regions.
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Mutations in this gene are associated with progressive epilepsy with mental retardation (EPMR), a subtype of neuronal ceroid lipofuscinosis (NCL). Patients with mutations in this gene have altered levels of sphingolipid and phospholipids in the brain.
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Phosphatidylinositol transfer protein (PITP) or priming in exocytosis protein 3 (PEP3) is a ubiquitous cytosolic domain involved in transport of phospholipids from their site of synthesis in the endoplasmic reticulum and Golgi to other cell membranes.
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The phospholipid bilayer is most permeable to small, uncharged solutes. Protein channels float through the phospholipids, and, collectively, this model is known as the fluid mosaic model. Aquaporins are protein channel pores permeable to H2O water.
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At first, amniotic fluid is mainly water with electrolytes, but by about the 12-14th week the liquid also contains proteins, carbohydrates, lipids and phospholipids, and urea, all of which aid in the growth of the fetus.
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Glycerophospholipids have three components: fatty acid lipid groups (orange), glycerol (white), and phosphate ester (green) Examples of variable phosphate esters in glycerophospholipids Glycerophospholipids or phosphoglycerides are glycerol-based phospholipids. They are the main component of biological membranes.
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PAP regulates lipid metabolism in several ways. In short, PAP is a key player in controlling the overall flux of triacylglycerols to phospholipids and vice versa, also exerting control through the generation and degradation of lipid-signaling molecules related to phosphatidate. When PAP is active, diacylglycerols formed by PAP can go on to form any of several products, including phosphatidylethanolamine, phosphatidylcholine, phosphatidylserine, and triacylglycerol. Phospholipids can be formed from diacylglycerol through reaction with activated alcohols, and triacylglycerols can be formed from DAG through reaction with fatty acyl CoA molecules.
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Plant thylakoid membranes have the largest lipid component of a non-bilayer forming monogalactosyl diglyceride (MGDG), and little phospholipids; despite this unique lipid composition, chloroplast thylakoid membranes have been shown to contain a dynamic lipid-bilayer matrix as revealed by magnetic resonance and electron microscope studies. Self- organization of phospholipids: a spherical liposome, a micelle, and a lipid bilayer. A biological membrane is a form of lamellar phase lipid bilayer. The formation of lipid bilayers is an energetically preferred process when the glycerophospholipids described above are in an aqueous environment.
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The structure of apolipoprotein(a) is similar to plasminogen and tPA (tissue plasminogen activator) and it competes with plasminogen for its binding site, leading to reduced fibrinolysis. Also, because Lp(a) stimulates secretion of PAI-1, it leads to thrombogenesis. It also may enhance coagulation by inhibiting the function of tissue factor pathway inhibitor. Moreover, Lp(a) carries atherosclerosis-causing cholesterol and binds atherogenic pro-inflammatory oxidised phospholipids as a preferential carrier of oxidised phospholipids in human plasma, which attracts inflammatory cells to vessel walls and leads to smooth muscle cell proliferation.
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One proposal showed two methods that led to the cytotoxicity in U87 and A172 glioblastoma cells. The first method showed CTAB exchanging with phospholipids causing rearrangement of the membrane allowing β-galactoside to enter into the cell by way of cavities. At low concentrations, there are not enough cavities to cause death to the cells, but with increasing the CTAB concentration, more phospholipids are displaced causing more cavities in the membrane leading to cell death. The second proposed method is based on the dissociation of CTAB into CTA+ and Br− within the mitochondrial membrane.
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Each of the envelope membranes is a lipid bilayer that is between 6 and 8 nm thick. The lipid composition of the outer membrane has been found to be 48% phospholipids, 46% galactolipids and 7% sulfolipids, while the inner membrane has been found to contain 16% phospholipids, 79% galactolipids and 5% sulfolipids in spinach chloroplasts. The outer membrane is permeable to most ions and metabolites, but the inner membrane of the chloroplast is highly specialised with transport proteins. For example, carbohydrates are transported across the inner envelope membrane by a triose phosphate translocator.
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The phospholipids are amphiphilic. The hydrophilic end usually contains a negatively charged phosphate group, and the hydrophobic end usually consists of two "tails" that are long fatty acid residues. In aqueous solutions, phospholipids are driven by hydrophobic interactions that result in the fatty acid tails aggregating to minimize interactions with water molecules. The result is often a phospholipid bilayer: a membrane that consists of two layers of oppositely oriented phospholipid molecules, with their heads exposed to the liquid on both sides, and with the tails directed into the membrane.
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Surfactin, true to its antibiotic nature, has a very significant antibacterial property, as it is capable of penetrating the cell membranes of all types of bacteria. There are two main types of bacteria and they are Gram-negative and Gram-positive. The two bacteria types differ in the composition of their membrane. The Gram-negative bacteria have an outer lipopolysaccharide membrane and a thin peptidoglycan layer followed by a phospholipids bilayer, whereas the Gram-positive bacteria lack the outer membrane and carry a thicker peptidoglycan layer as well as a phospholipids bilayer.
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The principal defense molecules secreted by Paneth cells are alpha-defensins, which are known as cryptdins in mice. These peptides have hydrophobic and positively charged domains that can interact with phospholipids in cell membranes. This structure allows defensins to insert into membranes, where they interact with one another to form pores that disrupt membrane function, leading to cell lysis. Due to the higher concentration of negatively charged phospholipids in bacterial than vertebrate cell membranes, defensins preferentially bind to and disrupt bacterial cells, sparing the cells they are functioning to protect.
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The accumulation of these lipids can impair the normal function of multiple organ systems, as discussed above. In addition, these individuals can show deficient levels of plasmalogens, ether-phospholipids that are especially important for brain and lung function.
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Cottonseed Oil Processing Steps Once the crude oil is extracted, it must be processed and refined before it can be used for consumption, in order to remove impurities, including free fatty acids (FFA), phospholipids, pigments and volatile compounds.
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The length of the fatty acid chain could be related to the binding of the toxin to the membrane to be effective, as those phospholipids with longer tails prevent the toxin from getting close enough to the membrane.
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The gene encoding cytosolic phospholipase A2-α is found on chromosome 1. Cytosolic phospholipase A2-α acts on membrane phospholipids to release arachidonic acid a precursor in the synthesis of eicosanoids. The eicosanoids are involved in multiple regulatory pathways.
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1,2-CTD degrades phenolic hydrocarbons key to the synthesis lipid membranes. Therefore, 1,2-CTD may bind to the cell lipid membrane via its terminal phospholipids and thus have greater access to the phenolic hydrocarbons vital in lipid membrane structure.
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Cleviprex should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. Maintain aseptic technique while handling Cleviprex. Cleviprex contains phospholipids and can support microbial growth. Do not use if contamination is suspected.
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The semipermeable membrane is pertinent to cellular communication. A cell membrane consists of proteins and phospholipids. Signaling molecules send chemical messages to the proteins in the cell membrane. The signaling molecules bind to proteins, which alters the protein structure.
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The accumulation of these lipids can impair the normal function of multiple organ systems, as discussed below. In addition, these individuals can show deficient levels of plasmalogens, ether-phospholipids that are especially important for brain, lung, and heart functions.
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Industrially, alpha-GPC is produced by the chemical or enzymatic deacylation of phosphatidylcholine enriched soya phospholipids followed by chromatographic purification. Alpha-GPC may also be derived in small amounts from highly purified soy lecithin as well from purified sunflower lecithin.
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The major dietary lipids for humans and other animals are animal and plant triglycerides, sterols, and membrane phospholipids. The process of lipid metabolism synthesizes and degrades the lipid stores and produces the structural and functional lipids characteristic of individual tissues.
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In this technique, drug particles are enveloped in a plasma membrane-bound vesicle. Folate is attached to polyethylene glycol bound to the phosphate heads of membrane phospholipids, thus directing the liposomes to FRs of tumor cells, by which they are engulfed.
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15-lipoxygenase acts by binding to phospholipids and yields hydroperoxy and epoxy metabolites. One such metabolite, 15-hydroxyeicosatetranoic acid (15-HETE), is released intracellularly, where it conjugates to phosphatidylethanolamine, a phospholipid component. 15-HETE-PE induces expression of the mucin MUC5AC.
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Very-low-density lipoproteins transport endogenous triglycerides, phospholipids, cholesterol, and cholesteryl esters. It functions as the body's internal transport mechanism for lipids. In addition it serves for long-range transport of hydrophobic intercellular messengers, like the morphogen Indian hedgehog (protein).
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Dyslipidemia is an abnormal amount of lipids (e.g. triglycerides, cholesterol and/or fat phospholipids) in the blood. In developed countries, most dyslipidemias are hyperlipidemias; that is, an elevation of lipids in the blood. This is often due to diet and lifestyle.
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ATP is also important for phosphorylation, a key regulatory event in cells. Phospholipids are the main structural components of all cellular membranes. Calcium phosphate salts assist in stiffening bones. Biochemists commonly use the abbreviation "Pi" to refer to inorganic phosphate.
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A. salmonicida tests negative for indole formation, coagulase, hydrolysis of starch, casein, triglycerides, and phospholipids, hydrogen sulfide production, citrate use, phenylalanine, and the Voges–Proskauer (butanediol fermentation) test. It tests positive for oxidase, lysine decarboxylase, methyl red, gelatin hydrolysis, and catalase.
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These are important components for the formation of lipid bilayers. Phosphatidylethanoamines, phosphatidylcholines, and other phospholipids are examples of phosphatidates. ;Phosphatidylcholines Phosphatidylcholines are lecithins. Choline is the alcohol, with a positively charged quaternary ammonium, bound to the phosphate, with a negative charge.
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Annexin A-V is the major player when it comes to mechanisms of coagulation. Like other annexin types, annexin A-V can also be expressed on the cell surface and can function to form 2-dimensional crystals to protect the lipids of the cell membrane from involvement in coagulation mechanisms. Medically speaking, phospholipids can often be recruited in autoimmune responses, most commonly observed in cases of fetal loss during pregnancy. In such cases, antibodies against annexin A-V destroy its 2-dimensional crystal structure and uncover the phospholipids in the membrane, making them available for contribution to various coagulation mechanisms.
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The majority of reports on hepoxilin formation have not defined the pathways evolved. Human and other mammalian cytochrome P450 enzymes convert 12(S)-HpETE to 12-oxo-ETE. 12-HETE (stereoisomer not determined), 12(S)-HETE, 12-oxo-ETE, hepoxilin B3, and trioxilin B3 are found in the sn-2 position of phospholipids isolated from normal human epidermis and human psoriatic scales. This indicates that the metabolites are acylated into the sn-2 position after being formed and/or directly produced by the metabolism of the arachidonic acid at the sn-2 position of these phospholipids.
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Scheme of a micelle spontaneously formed by phospholipids in an aqueous solution When phospholipids are placed in water, the molecules spontaneously arrange such that the tails are shielded from the water, resulting in the formation of membrane structures such as bilayers, vesicles, and micelles. In modern cells, vesicles are involved in metabolism, transport, buoyancy control, and enzyme storage. They can also act as natural chemical reaction chambers. A typical vesicle or micelle in aqueous solution forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single-tail regions in the micelle centre.
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Polybia paulista features a peptide Polybia-MP1 that causes increased permeability in cells featuring phospholipids phosphatidylserine (PS) and phosphatidylethanolamine (PE) on the outer membrane. As cancer cells feature the PS and PE phospholipids on the outside of the cell membrane, unlike with non-cancerous cells where they usually remain on the inside of the cell membrane, they are susceptible to the peptide which causes increased cell permeability to a degree that molecules critical for cell function may leak out. Further research is needed to ensure that Polybia-MP1 is safe for use as a chemotherapeutic drug.
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The toxicity of Taipoxin or other PLA2 toxins are often measured with their ability to cut short chain phospholipids or phospholipids- analogues. For Taipoxin PLA2 activity was set on 0.4 mmol/min/mg, and the binding constant (K) of taipoxin would be equal to: KTaipoxin = KA \+ KB \+ KC as it consist out of 3 enzymatic domains/subunits. However no correlation was made between PLA2 activity and toxicity, as the pharmacokinetics and the membrane binding properties are more important. A more specific membrane binding would lead to accumulation of taipoxin in the plasma membranes of motor-neurons.
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The availability of cholesterol at the membrane surface is dependent upon its interaction with other membrane components such as phospholipids and proteins; and the more cholesterol interacts with these components the less available it is to interact with extramembranous molecules. Some factors that affect cholesterols availability are size of the polar head groups and the ability of the phospholipid to hydrogen bond with the 3-β-OH group of cholesterol. Cholesterol associates with phospholipids, forming a stoichiometric complex and contributes to membrane fluidity. If cholesterol concentration exceeds a certain point, free cholesterol will begin to precipitate out of the membrane.
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Fat in meat can be either adipose tissue, used by the animal to store energy and consisting of "true fats" (esters of glycerol with fatty acids), or intramuscular fat, which contains considerable quantities of phospholipids and of unsaponifiable constituents such as cholesterol.
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The most common biological zwitterionic surfactants have a phosphate anion with an amine or ammonium, such as the phospholipids phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, and sphingomyelins. Lauryldimethylamine oxide and myristamine oxide are two commonly used zwitterionic surfactants of the tertiary amine oxides structural type.
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The PI3-kinase activity of this protein is sensitive to low nanomolar levels of the inhibitor wortmannin. The C2 domain of this protein was shown to bind phospholipids but not Ca2+, which suggests that this enzyme may function in a calcium- independent manner.
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However the gastric lipase activity against phospholipids and cholesterol esters is poor. Gastric lipase is composed of 379 amino acids. Fully glycosylated protein is 50kDa and unglycosylated enzyme is 43kDa. However deglycosylation of the enzyme does not affect the activity of the enzyme.
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WIPI-3 is a member of the WIPI or SVP1 family of WD40 repeat-containing proteins. The protein contains seven WD40 repeats that are thought to fold into a beta-propeller structure that mediates protein–protein interactions, and a conserved motif for interaction with phospholipids.
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Annexins are characterized by their calcium dependent ability to bind to negatively charged phospholipids (i.e. membrane walls). They are located in some but not all of the membranous surfaces within a cell, which would be evidence of a heterogeneous distribution of Ca2+ within the cell.
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It sources its versatile capacity for degradation by import of enzymes with specificity for different substrates; cathepsins are the major class of hydrolytic enzymes, while lysosomal alpha-glucosidase is responsible for carbohydrates, and lysosomal acid phosphatase is necessary to release phosphate groups of phospholipids.
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Red blood cells, or erythrocytes, have a unique lipid composition. The bilayer of red blood cells is composed of cholesterol and phospholipids in equal proportions by weight. Erythrocyte membrane plays a crucial role in blood clotting. In the bilayer of red blood cells is phosphatidylserine.
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Common sources of industrially produced phospholipids are soya, rapeseed, sunflower, chicken eggs, bovine milk, fish eggs etc. Each source has a unique profile of individual phospholipid species as well as fatty acids and consequently differing applications in food, nutrition, pharmaceuticals, cosmetics and drug delivery.
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Phosphatidylinositol transfer protein alpha isoform is a protein that in humans is encoded by the PITPNA gene. Phosphatidylinositol transfer proteins are a diverse set of cytosolic phospholipid transfer proteins that are distinguished by their ability to transfer phospholipids between membranes in vitro (Wirtz, 1991).
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They target molecules such as phospholipids, nucleic acids, and ATP. Class B metals are metals that form soft acids. Soft acids are acids with relatively covalent bonds. These metals, such as lead, gold, palladium, platinum, mercury, and rhodium, would rather bond with iodine than fluorine.
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The catalytic conversion of uridine triphosphate (UTP) to cytidine triphosphate (CTP) is accomplished by the enzyme cytidine-5-prime-triphosphate synthetase. This enzyme is important in the biosynthesis of phospholipids and nucleic acids, and plays a key role in cell growth, development, and tumorigenesis.
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The MAM is enriched in enzymes involved in lipid biosynthesis, such as phosphatidylserine synthase on the ER face and phosphatidylserine decarboxylase on the mitochondrial face. Because mitochondria are dynamic organelles constantly undergoing fission and fusion events, they require a constant and well-regulated supply of phospholipids for membrane integrity. But mitochondria are not only a destination for the phospholipids they finish synthesis of; rather, this organelle also plays a role in inter-organelle trafficking of the intermediates and products of phospholipid biosynthetic pathways, ceramide and cholesterol metabolism, and glycosphingolipid anabolism. Such trafficking capacity depends on the MAM, which has been shown to facilitate transfer of lipid intermediates between organelles.
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These specific properties allow phospholipids to play an important role in the cell membrane. Their movement can be described by the fluid mosaic model, that describes the membrane as a mosaic of lipid molecules that act as a solvent for all the substances and proteins within it, so proteins and lipid molecules are then free to diffuse laterally through the lipid matrix and migrate over the membrane. Sterols contribute to membrane fluidity by hindering the packing together of phospholipids. However, this model has now been superseded, as through the study of lipid polymorphism it is now known that the behaviour of lipids under physiological (and other) conditions is not simple.
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Phospholipids, a class of amphiphilic molecules, are the main components of biological membranes. The amphiphilic nature of these molecules defines the way in which they form membranes. They arrange themselves into bilayers, by positioning their polar groups towards the surrounding aqueous media (respectively the extracellular fluid and the intracellular solution, the cytosol), and their lipophilic chains towards the inside of the bilayer, defining a non-polar region between the two polar ones. Although phospholipids are the principal constituents of biological membranes, there are other constituents, such as cholesterol and glycolipids, which are also included in these structures and give them different physical and biological properties.
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One or both of these mechanisms appears to contribute to the ability of certain highly reactive PUFA- cyclopenetenones to exhibit SPM activity. The PUFA-cyclopentenones include two prostaglandins, (PG) Δ12-PGJ2 and 15-deoxy-Δ12,14-PGJ2, and two isoprostanes, 5,6-epoxyisoprostane E2 and 5,6-epoxyisoprostane A2. Both PGJ2's are arachidonic acid-derived metabolites made by cyclooxygenases, primarily COX-2, which is induced in many cell types during inflammation. Both isoprostanes form non-enzymatically as a result the attack on the arachidonic acid bond to cellular phospholipids by reactive oxygen species; they are then release from the phospholipids to become free in attacking their target proteins.
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Some species of vascular plants also contain intracellular structures called oil bodies. Vascular plant oil bodies consist mainly of triacylglycerols surrounded by a layer consisting of phospholipids and the protein oleosin. These oil bodies occur largely in seeds but also occur in other plant parts, including leaves.
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The PH domain is involved in intracellular targeting of the DH domain. It is generally thought to modulate membrane binding through interactions with phospholipids, but its function has been shown to vary in different proteins. This PH domain is also present in other proteins beyond RhoGEFs.
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This gene encodes a protein which contains a FYVE zinc finger binding domain. The presence of this domain is thought to target these proteins to Membrane lipids through interaction with Phospholipids in the membrane. Mutations in this gene are associated with autosomal recessive spastic paraplegia-15.
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Hsp-70 has also been linked to aiding granzyme B entry. Granzyme B has also been proposed to enter a target by first exchanging its bound serglycin for negative phospholipids in a target's plasma membrane. Entry then occurs by the less selective process of absorptive pinocytosis.
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Methanohalophilus mahii cells stain Gram negative, and are non-motile, irregular cocci approximately 0.8 to 1.8 micrometers in diameter. Additionally, the cells fluoresce under 420 nanometer light. Membrane phospholipids are composed of β-hydroxyarchaeol cores, glucose glycolipids, and ethanolamine, glycerol, and myo-inositol polar head groups.
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The phospholipids are stored in the lamellar bodies. Without this coating, the alveoli would collapse. The surfactant is continuously released by exocytosis. Reinflation of the alveoli following exhalation is made easier by the surfactant, which reduces surface tension in the thin fluid coating of the alveoli.
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An example of a phosphatidylcholine, a type of phospholipid in egg lecithin. Red - choline and phosphate group; Black - glycerol; Green - unsaturated fatty acid; Blue - saturated fatty acid Egg lecithin is a type of lecithin, a group of compounds primarily containing phospholipids, that is derived from eggs.
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Dietary sources involved in the construction of lipid raft, n-3 PUFA from oil fish as well as polyphenols, affect the molecular and structural shape of the phospholipids in the membrane. As such, this organisation model contributes to distinguishing effects of perturbations on cell membrane order and fluidity.
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Moreover, Prochlorococcus have adapted to use sulfolipids instead of phospholipids in their membranes to survive in phosphate deprived environments. This adaptation allows them to avoid competition with heterotrophs that are dependent on phosphate for survival. Typically, Prochlorococcus divide once a day in the subsurface layer or oligotrophic waters.
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This process is similar to the mechanism of contraction in a muscle cell. The entire OCS thus becomes indistinguishable from the initial platelet membrane as it forms the "fried egg". This dramatic increase in surface area comes about with neither stretching nor adding phospholipids to the platelet membrane.
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Bile acids comprise about 80% of the organic compounds in bile (others are phospholipids and cholesterol). An increased secretion of bile acids produces an increase in bile flow. Bile acids facilitate digestion of dietary fats and oils. They serve as micelle-forming surfactants, which encapsulate nutrients, facilitating their absorption.
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Overall, the monomer interchanging process is necessary in order to demonstrate the nearest neighbor recognition technique effective by observing changes in the phase composition of the host membranes/phospholipids. Each model membrane consists of a high concentration of one of the host membranes/phospholipids (95% mol %), low concentrations of two exchanging lipids (2.5 mol% each for a total of 5%), varied mole percentages of cholesterol (0–30 mol %) plus a constant concentration of ethanol (5% v/v). An aqueous buffer solution contains the 5% ethanol (v/v) which is desired but due to evaporation, the value is lowered to approximately 2.9% ethanol. ;Significance of research: All experiments are carried out at 60 °C.
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Biological bilayers are usually composed of amphiphilic phospholipids that have a hydrophilic phosphate head and a hydrophobic tail consisting of two fatty acid chains. Phospholipids with certain head groups can alter the surface chemistry of a bilayer and can, for example, serve as signals as well as "anchors" for other molecules in the membranes of cells. Just like the heads, the tails of lipids can also affect membrane properties, for instance by determining the phase of the bilayer. The bilayer can adopt a solid gel phase state at lower temperatures but undergo phase transition to a fluid state at higher temperatures, and the chemical properties of the lipids' tails influence at which temperature this happens.
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Fatty acids are usually not found in organisms in their standalone form, but instead exist as three main classes of esters: triglycerides, phospholipids, and cholesteryl esters. In any of these forms, fatty acids are both important dietary sources of fuel for animals and they are important structural components for cells.
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Together with nitrogen, arsenic, antimony, and bismuth, phosphorus is classified as a pnictogen. Phosphorus is essential for life. Phosphates (compounds containing the phosphate ion, PO43−) are a component of DNA, RNA, ATP, and phospholipids. Elemental phosphorus was first isolated from human urine, and bone ash was an important early phosphate source.
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One of the serum substances which is part of the dissolution process of bacteria, the enzymes will promote the dissolution of the bacterial cell wall and cause the death of the bacteria. Bacteriolysin probably functions by deregulating lipoteichoic acid (LTA) in Gram-positive bacteria and phospholipids in Gram-negative bacteria.
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Methionine is an intermediate in the biosynthesis of cysteine, carnitine, taurine, lecithin, phosphatidylcholine, and other phospholipids. Improper conversion of methionine can lead to atherosclerosis due to accumulation of homocysteine. Methionine might also be essential to reversing damaging methylation of glucocorticoid receptors caused by repeated stress exposures, with implications for depression.
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But also plays an important role in the energy supply. In addition phosphorus acts as a buffer, is involved in phospholipids and fatty acids transfer, in the formation of amino acids and in makes part of DNA and RNA. Therefore, phosphorus is indispensable for live and animals cannot live without.
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Meclofenoxate (INN, BAN; brand name Lucidril, also known as centrophenoxine) is a cholinergic nootropic used as a dietary supplement. It is an ester of dimethylethanolamine (DMAE) and 4-chlorophenoxyacetic acid (pCPA). In elderly patients, meclofenoxate has been shown to improve performance on certain memory tests. Meclofenoxate also increases cellular membrane phospholipids.
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Ethanolamine is biosynthesized by decarboxylation of serine: :HOCH2CH(CO2H)NH2 → HOCH2CH2NH2 \+ CO2 Ethanolamine is the second-most- abundant head group for phospholipids, substances found in biological membranes (particularly those of prokaryotes); e.g., phosphatidylethanolamine. It is also used in messenger molecules such as palmitoylethanolamide, which has an effect on CB1 receptors.
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It seems to do so by blocking the phosphorylation of MARCKS. It is thought that the dendrotoxin-like B chain acts first by inhibition of ion channels, causing cessation of twitches followed by a prolonged facilitatory phase. The A chain (bearing phospholipase activity) then induces a blocking phase by destruction of phospholipids.
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Dock6 was identified as one of a family of proteins which share high sequence similarity with Dock180, the archetypal member of the DOCK family. It has a similar domain arrangement to other DOCK proteins, with a DHR1 domain known in other proteins to bind phospholipids, and a DHR2 domain containing the GEF activity.
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It has been proposed that FerA may be involved in membrane interaction as well. It can in fact interact with neutral or negatively charged phospholipids and the interaction is enhanced in the presence of calcium ions. The molecular mechanism by which FerA interacts with the membrane or calcium ions however, is currently unknown.
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Excessive consumption of choline (greater than 7.5 g/day) can cause low blood pressure, sweating, diarrhea and fish-like body odor due to trimethylamine, which forms in its metabolism. Rich dietary sources of choline and choline phospholipids include hen egg yolk, wheat germ, and meats, especially organ meats, such as beef liver.
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Activation may also to cause CERK to localize within endosomes. CERK’s PH domain plays an integral role in this localization. Once localized, to the trans-golgi CERK activates cytosolic phospholipase A2 (cPLA2) that has localized to the trans-golgi. Activation of cPLA2 results in hydrolysis of membrane phospholipids to produce arachidonic acid.
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Phosphatidylethanolamine Glycerophospholipids, usually referred to as phospholipids (though sphingomyelins are also classified as phospholipids), are ubiquitous in nature and are key components of the lipid bilayer of cells, as well as being involved in metabolism and cell signaling. Neural tissue (including the brain) contains relatively high amounts of glycerophospholipids, and alterations in their composition has been implicated in various neurological disorders. Glycerophospholipids may be subdivided into distinct classes, based on the nature of the polar headgroup at the sn-3 position of the glycerol backbone in eukaryotes and eubacteria, or the sn-1 position in the case of archaebacteria. Examples of glycerophospholipids found in biological membranes are phosphatidylcholine (also known as PC, GPCho or lecithin), phosphatidylethanolamine (PE or GPEtn) and phosphatidylserine (PS or GPSer).
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In the blood Lp-PLA2 travels mainly with low-density lipoprotein (LDL). Less than 20% is associated with high-density lipoprotein HDL. Several lines of evidence suggest that HDL-associated Lp-PLA2 may substantially contribute to the HDL antiatherogenic activities. It is an enzyme produced by inflammatory cells and hydrolyzes oxidized phospholipids in LDL.
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Schematic illustration of a MSP nanodisc with a 7-transmembrane protein embedded. Diameter is about 10 nm. Picture from Sligar Lab A nanodisc is a synthetic model membrane system which assists in the study of membrane proteins. It is composed of a lipid bilayer of phospholipids with the hydrophobic edge screened by two amphipathic proteins.
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In the plasma membrane, flippases transfer specific phospholipids selectively, so that different types become concentrated in each monolayer. Using selective flippases is not the only way to produce asymmetry in lipid bilayers, however. In particular, a different mechanism operates for glycolipids—the lipids that show the most striking and consistent asymmetric distribution in animal cells.
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Calmodulin, when activated by calcium may bind weakly to the CH domain and inhibit calponin binding with α-actin. Calponin is responsible for binding many actin binding proteins, phospholipids, and regulates the actin/myosin interaction. Calponin is also thought to negatively affect the bone making process due to being expressed in high amounts in osteoblasts.
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At the bottom is the common phospholipid, phosphatidylcholine.Voet (2005), Ch. 12 Lipids and Membranes. Lipids comprise a diverse range of molecules and to some extent is a catchall for relatively water-insoluble or nonpolar compounds of biological origin, including waxes, fatty acids, fatty-acid derived phospholipids, sphingolipids, glycolipids, and terpenoids (e.g., retinoids and steroids).
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KP Talaro Foundations in Microbiology, McGraw Hill 6thEd. It acts as regulator of autolytic wall enzymes (muramidases). It has antigenic properties being able to stimulate specific immune response. Structure of the lipoteichoic acid polymer LTA may bind to target cells non-specifically through membrane phospholipids, or specifically to CD14 and to Toll-like receptors.
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It was not until much later that the subcomponents of thromboplastin and partial thromboplastin were identified. Thromboplastin contains phospholipids as well as tissue factor, both of which are needed in the activation of the extrinsic pathway, whereas partial thromboplastin does not contain tissue factor. Tissue factor is not needed to activate the intrinsic pathway.
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It has been proposed to be conjugated from arachidonoyl-CoA or arachidonoyl phospholipids and dopamine, but in vitro experiments do not support this theory. However, the indirect biosynthesis of phospholipid esters with dopamine may be possible, as dopamine can induce the aminolysis of the glycerol-fatty acid bonds in phospholipid chains (arachidonoyl, palmitoyl, linoleyl, etc.).
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Schematic of a Cytomegalovirus A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life-cycle when traveling between host cells. Not all viruses have envelopes. The envelopes are typically derived from portions of the host cell membranes (phospholipids and proteins), but include some viral glycoproteins.
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Initially milk fat is secreted in the form of a fat globule surrounded by a membrane.Fox, P.F. Advanced Dairy Chemistry: Vol 2 Lipids. 2nd Ed. Chapman and Hall: New York, 1995. Each fat globule is composed almost entirely of triacylglycerols and is surrounded by a membrane consisting of complex lipids such as phospholipids, along with proteins.
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WD40 repeat proteins are key components of many essential biologic functions. They regulate the assembly of multiprotein complexes by presenting a beta-propeller platform for simultaneous and reversible protein–protein interactions. Members of the WIPI subfamily of WD40 repeat proteins, such as WIPI1, have a 7-bladed propeller structure and contain a conserved motif for interaction with phospholipids.
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TPTE is a member of a large class of membrane-associated phosphatases with substrate specificity for the 3-position phosphate of inositol phospholipids. TPTE is a primate-specific duplicate of the TPTE2 (TPIP) inositol phospholipd phosphatase; TPTE itself is predicted to lack phosphatase activity. TPTE and TPTE2 are the mammalian homologues to the subfamily of voltage sensitive phosphatases.
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469 The thylakoid lipid bilayer shares characteristic features with prokaryotic membranes and the inner chloroplast membrane. For example, acidic lipids can be found in thylakoid membranes, cyanobacteria and other photosynthetic bacteria and are involved in the functional integrity of the photosystems. The thylakoid membranes of higher plants are composed primarily of phospholipids"photosynthesis."Encyclopædia Britannica. 2008.
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Encyclopædia Britannica 2006 Ultimate Reference Suite DVD 9 Apr. 2008 and galactolipids that are asymmetrically arranged along and across the membranes. Thylakoid membranes are richer in galactolipids rather than phospholipids; also they predominantly consist of hexagonal phase II forming monogalacotosyl diglyceride lipid. Despite this unique composition, plant thylakoid membranes have been shown to assume largely lipid-bilayer dynamic organization.
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While no drugs targeting NAAA have entered the market yet, there is currently substantial research being done on the activation, and specific targeting and inhibition of NAAA. Activation of NAAA is spurred by the addition of phospholipids, and targeted inhibition by different buffers. Findings in these areas may be able to develop drugs to combat chronic pain and obesity.
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Examples of amphiphilic compounds are the salts of fatty acids, phospholipids. Many simple amphiphiles are used as detergents. A mixture of soap and water is an everyday example of a lyotropic liquid crystal. Biological structures such as fibrous proteins showings relatively long and well-defined hydrophobic and hydrophilic ‘‘blocks’’ of aminoacids can also show lyotropic liquid crystalline behaviour.
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The proteins are mostly alpha-helical, and the dimer is formed in an antiparallel way. The dimer interface features a cavity formed across the two monomers, which can accommodate small to medium sized ligands like steroids and phospholipids. The binding and release may be coupled with the redox state of the cystines, i.e. the presence of these disulfide bonds.
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Steroids and their metabolites often function as signalling molecules (the most notable examples are steroid hormones), and steroids and phospholipids are components of cell membranes. Steroids such as cholesterol decrease membrane fluidity. Similar to lipids, steroids are highly concentrated energy stores. However, they are not typically sources of energy; in mammals, they are normally metabolized and excreted.
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They accomplish this by being exposed to the extracellular face of the cell membrane after the inactivation of flippases which place them exclusively on the cytosolic side and the activation of scramblases, which scramble the orientation of the phospholipids. After this occurs, other cells recognize the phosphatidylserines and phagocytosize the cells or cell fragments exposing them.
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Wendy Boss is an American botanist and the current William Neal Reynolds Distinguished Professor Emeritus at North Carolina State University. Her research focuses on plant physiology and phosphoinositide mediated signalling in plants. Phosphoinositols are derived from the phospholipids found in plasma membrane of the cell. Phosphoinositols are known to be key molecules in signal transduction pathways.
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The fatty acids of the genus Salisediminibacterium mostly consist of anteiso-C15 : 0, anteiso-C17 : 0 and iso-C15 : 0. The cell-wall peptidoglycan contains the diagnostic diamino acid meso-diaminopimelic acid. The predominant menaquinone is MK-7. The polar lipids include four phospholipids (PL1, 3, 5 and 6) including diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol and an unknown aminophospholipid (APL1).
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The hallmark feature of ferroptosis is the iron- dependent accumulation of oxidatively damaged phospholipids (i.e. lipid peroxides). This occurs when free radical molecules take electrons from a lipid molecule, promoting their oxidation by oxygen. The primary cellular mechanism of protection against ferroptosis is mediated by GPX4, a glutathione-dependent peroxidase that converts lipid peroxides into non-toxic lipid alcohols.
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Human cells release arachidonic acid (i.e. 5Z,8Z,11Z,14Z-eicosatetraenoic acid) from its storage site in phospholipids by reactions that involve phospholipase C and/or lipase enzymes. This release is stimulated or enhanced by cell stimulation. The freed arachidonic acid is then converted to 15-hydroperoxy/hydroxy products by one or more of the following five pathways.
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06 to 2.92 ± .05 which relates to the distance between the phosphorus atoms on opposite sides of the membrane. The study also supports the fact that ethanol prefers to bond just below the hydrophilic region of the phospholipids near the phosphate groups. The location of the ethanol creates a strong hydrogen bond between the water molecules.
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1-acyl-sn-glycerol-3-phosphate acyltransferase alpha is an enzyme that in humans is encoded by the AGPAT1 gene. This gene encodes an enzyme that converts lysophosphatidic acid (LPA) into phosphatidic acid (PA). LPA and PA are two phospholipids involved in signal transduction and in lipid biosynthesis in cells. This enzyme localizes to the endoplasmic reticulum.
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CF1 bound to membranes was found to be much more resistant to heat and cold than solubilised protein. Mitochondrial coupling factor F1 is similarly protected by phospholipids and SQDGs although, in that case, both were equally effective.Bennun and Racker, 1969Livn and Racker, 1969 Information about SQDG and the Rieske protein interaction in the cyt b6f structures is also present.
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The cells of Methanofollis are highly irregular cocci, with diameter of 1.25-2.0 µm. The major polar lipids are phospholipids, glycolipids, and phosphoglycolipids. It utilizes H2/CO2, formate, 2-propanol/CO2, and 2-butanol/CO2 for growth and methanogenesis. No growth has been observed on acetate, trimethylamine, methanol, ethanol, 2-propanol, isobutanol, or 2-butanol as catabolic substrates.
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The conserved domain of this protein possesses the binding activities to Ca++-calmodulin, actin, tropomyosin, myosin, and phospholipids. This protein is a potent inhibitor of the actin-tropomyosin activated myosin MgATPase, and serves as a mediating factor for Ca++-dependent inhibition of smooth muscle contraction. Alternative splicing of this gene results in multiple transcript variants encoding distinct isoforms.
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This gene encodes a member of the membrane- bound O-acyltransferases family of integral membrane proteins that have acyltransferase activity. The encoded protein is a lysophosphatidylinositol acyltransferase that has specificity for arachidonoyl-CoA as an acyl donor. This protein is involved in the re-acylation of phospholipids as part of the phospholipid remodeling pathway known as the Land cycle.
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Clotrimazole is an imidazole derivative which works by inhibiting the growth of individual Candida or fungal cells by altering the permeability of the fungal cell wall. It binds to phospholipids in the cell membrane and inhibits the biosynthesis of ergosterol and other sterols required for cell membrane production. Clotrimazole may slow fungal growth or result in fungal cell death.
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Gangliosides are present and concentrated on cell surfaces, with the two hydrocarbon chains of the ceramide moiety embedded in the plasma membrane and the oligosaccharides located on the extracellular surface, where they present points of recognition for extracellular molecules or surfaces of neighboring cells. They are found predominantly in the nervous system where they constitute 6% of all phospholipids.
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Unlike plant cells, animal cells have neither a cell wall nor chloroplasts. Vacuoles, when present, are more in number and much smaller than those in the plant cell. The body tissues are composed of numerous types of cell, including those found in muscles, nerves and skin. Each typically has a cell membrane formed of phospholipids, cytoplasm and a nucleus.
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Phospholipid arrangement in cell membranes. Phosphatidylcholine is the major component of lecithin. It is also a source for choline in the synthesis of acetylcholine in cholinergic neurons. Phospholipids (PL) are a class of lipids whose molecule has a hydrophilic "head" containing a phosphate group, and two hydrophobic "tails" derived from fatty acids, joined by an alcohol residue.
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That is the dominant structural motif of the membranes of all cells and of some other biological structures, such as vescicles or virus coatings. Phospholipid bilayers are the main structural component of cell membranes. In biological membranes, the phospholipids often occur with other molecules (e.g., proteins, glycolipids, sterols) in a bilayer such as a cell membrane.
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The combination provides fluidity in two dimensions combined with mechanical strength against rupture. Purified phospholipids are produced commercially and have found applications in nanotechnology and materials science. The first phospholipid identified in 1847 as such in biological tissues was lecithin, or phosphatidylcholine, in the egg yolk of chickens by the French chemist and pharmacist Theodore Nicolas Gobley.
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Phospholipids are optically highly birefringent, i.e. their refractive index is different along their axis as opposed to perpendicular to it. Measurement of birefringence can be achieved using cross polarisers in a microscope to obtain an image of e.g. vesicle walls or using techniques such as dual polarisation interferometry to quantify lipid order or disruption in supported bilayers.
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The intracellular, group IV PLA2 are also Ca-dependent, but they have a different 3D structure and are significantly larger than secreted PLA2 (more than 700 residues). They include a C2 domain and a large catalytic domain. These phospholipases are involved in cell signaling processes, such as inflammatory response. They release arachidonic acid from membrane phospholipids.
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Lipid-containing foods undergo digestion within the body and are broken into fatty acids and glycerol, which are the final degradation products of fats and lipids. Lipids, especially phospholipids, are also used in various pharmaceutical products, either as co- solubilisers (e.g., in parenteral infusions) or else as drug carrier components (e.g., in a liposome or transfersome).
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Immune stimulating complexes (ISCOMs) are spherical open cage-like structures (typically 40 nm in diameter) that are spontaneously formed when mixing together cholesterol, phospholipids and Quillaja saponins under a specific stoichiometry. The complex displays immune stimulating properties and is thus mainly used as a vaccine adjuvant in order to induce a stronger immune response and longer protection.
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Rates of DHA production in women are 15% higher than in men. DHA is a major fatty acid in brain phospholipids and the retina. While the potential roles of DHA in the mechanisms of Alzheimer's disease are under active research, studies of fish oil supplements, which contain DHA, have failed to support claims of preventing cardiovascular diseases.
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There are thirteen kinds of mammalian phospholipase C that are classified into six isotypes (β, γ, δ, ε, ζ, η) according to structure. Each PLC has unique and overlapping controls over expression and subcellular distribution. Activators of each PLC vary, but typically include heterotrimeric G protein subunits, protein tyrosine kinases, small G proteins, Ca2+, and phospholipids.
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Assembly of organs, tissues, cells and subcellular components are in part determined by their physical properties. For example, the cell membrane that forms a barrier between the inside and outside of the cell is a lipid bilayer that forms as result of the thermodynamic properties of the phospholipids it's made of (hydrophilic head and hydrophobic tails).
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Another hypothesis is based on the specific binding with receptors and proteins to create intracellular enzyme dependent and independent reactions. Membrane damage by the PLA2 activity allows PLA2 to enter cells and specifically bind to proteins and receptors either agonistic or antagonistic, inducing pharmacological effects non-enzymatically. The intracellular PLA2 could also remain enzymatically active and hydrolyze membrane phospholipids.
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One proposed mechanism is that an increase in cell membrane fluidity, consisting largely of lipid, activates the insulin receptor. A decrease in MUFA content of the membrane phospholipids in the SCD-1−/− mice is offset by an increase in polyunsaturated fatty acids, effectively increasing membrane fluidity due to the introduction of more double bonds in the fatty acyl chain.
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This enzyme participates in streptomycin biosynthesis and inositol phosphate metabolism. It employs one cofactor, NAD+. The reaction this enzyme catalyses represents the first committed step in the production of all inositol-containing compounds, including phospholipids, either directly or by salvage. The enzyme exists in a cytoplasmic form in a wide range of plants, animals, and fungi.
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Hydrogen and oxygen are found in water and organic molecules, both of which are essential to life. Carbon is found in all organic molecules, whereas nitrogen is an important component of nucleic acids and proteins. Phosphorus is used to make nucleic acids and the phospholipids that comprise biological membranes. Sulfur is critical to the three-dimensional shape of proteins.
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Biosynthesis of Phosphatidylethanolamine in Bacteria Phosphatidylethanolamines are a class of phospholipids found in biological membranes. They are synthesized by the addition of cytidine diphosphate-ethanolamine to diglycerides, releasing cytidine monophosphate. S-Adenosyl methionine can subsequently methylate the amine of phosphatidylethanolamines to yield phosphatidylcholines. It can mainly be found in the inner (cytoplasmic) leaflet of the lipid bilayer.
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Adipose differentiation-related protein, also known as perilipin 2 , ADRP or adipophilin, is a protein which belongs from PAT family of cytoplasmic lipid droplet(CLD) binding protein. In humans it is encoded by the ADFP gene. This protein surrounds the lipid droplet along with phospholipids and are involved in assisting the storage of neutral lipids within the lipid droplets.
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Choline is needed to produce acetylcholine. This is a neurotransmitter which plays a necessary role in muscle contraction, memory and neural development, for example. Nonetheless, there is little acetylcholine in the human body relative to other forms of choline. Neurons also store choline in the form of phospholipids to their cell membranes for the production of acetylcholine.
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Other simultaneously occurring mechanisms explaining the observed liver damage have also been suggested. For example, choline phospholipids are also needed in mitochondrial membranes. Their inavailability leads to the inability of mitochondrial membranes to maintain proper electrochemical gradient, which, among other things, is needed for degrading fatty acids via β-oxidation. Fat metabolism within liver therefore decreases.
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Amphiphiles are molecules that have both hydrophobic and hydrophilic domains. Detergents are composed of amphiphiles that allow hydrophobic molecules to be solubilized in water by forming micelles and bilayers (as in soap bubbles). They are also important to cell membranes composed of amphiphilic phospholipids that prevent the internal aqueous environment of a cell from mixing with external water.
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These three proteins are colocalized within spherical particles containing phospholipids and cholesterol. The protein components of TLF-2 include IgM and apolipoprotein A-I. Trypanolytic factors are found only in a few species, including humans, gorillas, mandrills, baboons and sooty mangabeys. This appears to be because haptoglobin-related protein and apolipoprotein L-1 are unique to primates.
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Decapacitation factor (DF) is composed of factors in seminal plasma which modulates the fertilizing ability of spermatozoa. The activity is achieved by interaction between cholesterol, phospholipids and fibronectin-like substances and delivered via small vesicles in seminal plasma. DF prevents onset of capacitation. Physiologically it is achieved through spermatozoal membrane stabilization by maintaining physiological cholesterol/phospholipid ratio.
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Phosphorylethanolamine or phosphoethanolamine is an ethanolamine derivative that is used to construct two different categories of phospholipids. One category termed a glycerophospholipid and the other a sphingomyelin, or more specifically within the sphingomyelin class, a sphingophospholipid. Phosphorylethanolamine is a polyprotic acid with two pKa values at 5.61 and 10.39. Phosphorylethanolamine has been falsely promoted as a cancer treatment.
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Phospholipid is available as an independent reagent or in combination with tissue factor as thromboplastin. Complete thromboplastin consists of tissue factor, phospholipids (since platelets were removed from blood sample being tested), and CaCl2 to reintroduce calcium ions which were chelated by sodium citrate originally used to prevent coagulation of the sample blood during transportation and/or storage.
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DHR1 ( _D_ OCK _h_ omology _r_ egion 1), also known as CZH1 or Docker1, is a protein domain of approximately 200–250 amino acids that is present in the DOCK family of signalling proteins. This domain binds phospholipids and so may assist in recruitment to cellular membranes. There is evidence that this domain may also mediate protein–protein interactions.
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According to the model, membrane proteins are in three classes based on how they are linked to the lipid bi-layer: # Integral proteins: Immersed in the bi-layer and held in place by the affinity of hydrophobic parts of the protein for the hydrophobic tails of phospholipids on interior of the layer. # Peripheral proteins: More hydrophilic, and thus are non-covalently linked to the polar heads of phospholipids and other hydrophilic parts of other membrane proteins on the surface of the membrane. # Lipid anchored proteins: Essentially hydrophilic, so, are also located on the surface of the membrane, and are covalently attached to lipid molecules embedded in the layer. As for the fluid nature of the membrane, the lipid components are capable of moving parallel to the membrane surface and are in constant motion.
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This allows it to travel through the blood via emulsification. Unbound cholesterol, being amphipathic, is transported in the monolayer surface of the lipoprotein particle along with phospholipids and proteins. Cholesterol esters bound to fatty acid, on the other hand, are transported within the fatty hydrophilic core of the lipoprotein, along with triglyceride. There are several types of lipoproteins in the blood.
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Glycolipid transfer protein is a cytosolic protein that catalyses the transfer of glycolipids between different intracellular membranes. It was discovered by Raymond J. Metz and Norman S. Radin in 1980 and partially purified and characterized in 1982. Recent reviews on structure and possible function are available. This protein transports primarily different glycosphingolipids and glyceroglycolipids between intracellular membranes, but not phospholipids.
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Spanning from amino acid 1886 until amino acid 1983, this domain is referred to as a Pleckstrin Homology domain in the BEACH domain. It has a PH because the fold of this domain is similar to the PH domain, but is not identical in the sequence of the canonical PH domains. The PH_BEACH domain is not able to bind phospholipids.
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It is usually available from sources such as egg yolk, marine sources, soybeans, milk, rapeseed, cottonseed, and sunflower oil. It has low solubility in water, but is an excellent emulsifier. In aqueous solution, its phospholipids can form either liposomes, bilayer sheets, micelles, or lamellar structures, depending on hydration and temperature. This results in a type of surfactant that usually is classified as amphipathic.
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Pantothenic acid is precursory to biosynthesis of coenzyme A (CoA), which is not only required for cellular respiration, but also serves a role in the synthesis of structural and functional brain cell components such as cholesterol, amino acids, fatty acids and phospholipids. Vitamin B5 also plays a more direct role in cognitive function by participating in the synthesis of steroid hormones and neurotransmitters.
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VSPs have been used as an tool to manipulate phospholipids in experimental settings. Because membrane potential can be controlled using patch clamp techniques, placing VSPs in a membrane allows for experimenters to rapidly dephosphorylate substrates of VSPs. VSPs' voltage sensors have also been used to engineer genetically encodable voltage sensitive fluorescent probes. These probes allow experimenters to visualize voltage in membranes using fluorescence.
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This accumulation of damage on the biological molecules changes the framework and leads to a reduction in the molecules' activity levels. Lipid peroxides accumulate in the membrane phospholipids, which in turn diminishes the mitochondrial membrane's effectiveness as a barrier. The process of DNA transcription and translation also acquires oxidative damage. The result is alterations in the base pairings of the DNA sequence.
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Alpha-synuclein is a protein that, in humans, is encoded by the SNCA gene. It is abundant in the brain, while smaller amounts are found in the heart, muscle and other tissues. In the brain, alpha-synuclein is found mainly at the tips of neurons in specialized structures called presynaptic terminals. Within these structures, alpha-synuclein interacts with phospholipids and proteins.
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Cell membranes are bilayer structures principally formed from phospholipids, molecules which have a highly water interactive, ionic phosphate head groups attached to two long alkyl tails. By contrast, fluorosurfactants are not amphiphilic or detergents because fluorocarbons are not lipophilic. Oxybenzone, a common cosmetic ingredient often used in sunscreens, is particularly penetrative because it is not very lipophilic.Hanson KM, Gratton E, Bardeen CJ. 2006.
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Phospholipidosis is a lysosomal storage disorder characterized by the excess accumulation of phospholipids in tissues. Certain cases may be triggered by medications. The traditional method to evaluate DIPL is visual confirmation of myeloid bodies in tissues by electron microscopy. Electron microscopy has limited utility to monitor DIPL in humans because of the invasive nature of acquiring patient tissue biopsy samples.
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Dirty- appearing white matter (referred to as DAWM like the former case) is defined as a region with ill-defined borders of intermediate signal intensity between that of normal-appearing white matter (NAWM) and that of plaque on T2-weighted and proton density imaging. It is probably created by loss of myelin phospholipids, detected by the short T2 component, and axonal reduction.
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Sphingomyelin consists of a phosphocholine head group, a sphingosine, and a fatty acid. It is one of the few membrane phospholipids not synthesized from glycerol. The sphingosine and fatty acid can collectively be categorized as a ceramide. This composition allows sphingomyelin to play significant roles in signaling pathways: the degradation and synthesis of sphingomyelin produce important second messengers for signal transduction.
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In RBC studies, 30% of the plasma membrane is lipid. However, for the majority of eukaryotic cells, the composition of plasma membranes is about half lipids and half proteins by weight. The fatty chains in phospholipids and glycolipids usually contain an even number of carbon atoms, typically between 16 and 20. The 16- and 18-carbon fatty acids are the most common.
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In the body PGF2α is synthesized in several distinct steps. First, Phospholipase A2 (PLA2) facilitates the conversion of phospholipids to Arachidonic Acid, the framework from which all prostaglandins are formed. The Arachidonic Acid then reacts with two Cyclooxygenase (COX) receptors, COX-1 and COX-2 to form Prostaglandin H2, an intermediate. Lastly, the compound reacts with Aldose Reductase (AKR1B1) to form PGF2α.
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The largest family includes known and putative adhesins. The other four families are porins, iron transporters, flagellum-associated proteins, and proteins of unknown function. Like other typical Gram-negative bacteria, the outer membrane of H. pylori consists of phospholipids and lipopolysaccharide (LPS). The O antigen of LPS may be fucosylated and mimic Lewis blood group antigens found on the gastric epithelium.
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Fatty acids (or their salts) often do not occur as such in biological systems. Instead fatty acids such as oleic acid occur as their esters, commonly triglycerides, which are the greasy materials in many natural oils. Oleic acid is the most common monounsaturated fatty acid in nature. It is found in fats (triglycerides), the phospholipids that make membranes, cholesterol esters, and wax esters.
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The liposome can be used as a vehicle for administration of nutrients and pharmaceutical drugs.Kimball's Biology Pages, "Cell Membranes." Liposomes can be prepared by disrupting biological membranes (such as by sonication). Liposomes are most often composed of phospholipids, especially phosphatidylcholine, but may also include other lipids, such as egg phosphatidylethanolamine, so long as they are compatible with lipid bilayer structure.
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This gene encodes a member of the cytosolic phospholipase A2 group IV family. The enzyme catalyzes the hydrolysis of membrane phospholipids to release arachidonic acid which is subsequently metabolized into eicosanoids. Eicosanoids, including prostaglandins and leukotrienes, are lipid-based cellular hormones that regulate hemodynamics, inflammatory responses, and other intracellular pathways. The hydrolysis reaction also produces lysophospholipids that are converted into platelet- activating factor.
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Scramblase is a protein responsible for the translocation of phospholipids between the two monolayers of a lipid bilayer of a cell membrane. In humans, phospholipid scramblases (PLSCRs) constitute a family of five homologous proteins that are named as hPLSCR1–hPLSCR5. Scramblases are not members of the general family of transmembrane lipid transporters known as flippases. Scramblases are distinct from flippases and floppases.
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SCD-1 deficiency has also been shown to reduce ceramide synthesis by downregulating serine palmitoyltransferase. This consequently increases the rate of beta- oxidation in skeletal muscle. In carbohydrate metabolism studies, knockout SCD-1 mice show increased insulin sensitivity. Oleate is a major constituent of membrane phospholipids and membrane fluidity is influenced by the ratio of saturated to monounsaturated fatty acids.
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Each member of the PKC family has a specific expression profile and is believed to play a distinct role in cells. The protein encoded by this gene is one of the PKC family members. It is a calcium-independent and phospholipids-dependent protein kinase. It is predominantly expressed in epithelial tissues and has been shown to reside specifically in the cell nucleus.
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This fluid lipid bilayer cross section is made up entirely of phosphatidylcholine. The three main structures phospholipids form in solution; the liposome (a closed bilayer), the micelle and the bilayer. The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules. These membranes are flat sheets that form a continuous barrier around all cells.
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The packing of lipids within the bilayer also affects its mechanical properties, including its resistance to stretching and bending. Many of these properties have been studied with the use of artificial "model" bilayers produced in a lab. Vesicles made by model bilayers have also been used clinically to deliver drugs. Biological membranes typically include several types of molecules other than phospholipids.
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Common feedstock used in biodiesel production include yellow grease (recycled vegetable oil), "virgin" vegetable oil, and tallow. Recycled oil is processed to remove impurities from cooking, storage, and handling, such as dirt, charred food, and water. Virgin oils are refined, but not to a food-grade level. Degumming to remove phospholipids and other plant matter is common, though refinement processes vary.
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Flippases are described as transporters that move lipids from the exoplasmic to the cytosolic face, while floppases transport in the reverse direction. Many cells maintain asymmetric distributions of phospholipids between their cytoplasmic and exoplasmic membrane leaflets.Lodish, H, Berk A, Matsudaira P, Kaiser CA, Krieger M, Scott MP, Zipursky SL, Darnell J. (2004). Molecular Cell Biology, 5th, New York: WH Freeman.
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Immunological responses could be the cause in many cases of infertility and miscarriage. Some immunological reasons that contribute to infertility are reproductive autoimmune failure syndrome, the presence of anti-phospholipid antibodies, and antinuclear antibodies. Anti-phospholipid antibodies are targeted toward the phospholipids of the cell membrane. Studies have shown that antibodies against phosphatidylserine, phosphatidylcholine, phosphatidylglycerol, phosphatidylinositol and phosphatidylethanolamine target the pre-embryo.
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Calcium-dependent phospholipase A2 is an enzyme that in humans is encoded by the PLA2G5 gene. This gene is a member of the secretory phospholipase A2 family. It is located in a tightly-linked cluster of secretory phospholipase A2 genes on chromosome 1. The encoded enzyme catalyzes the hydrolysis of membrane phospholipids to generate lysophospholipids and free fatty acids including arachidonic acid.
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Antiphospholipid syndrome is an autoimmune disease characterized by thrombosis and complications during pregnancy, often leading to fetal death. It is caused by the presence of antibodies against anionic phospholipids and β2-glycoprotein I (β2GPI). The anti-β2GPI antibodies are most prevalent in causing the symptoms of the disease. When bound by an antibody, β2GPI begins to interact with monocytes, endothelial cells, and platelets.
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Prostaglandins are local chemical messengers that exert multiple effects including but not limited to the transmission of pain information to the brain, modulation of the hypothalamic thermostat, and inflammation. They are produced in response to the stimulation of phospholipids within the plasma membrane of cells resulting in the release of arachidonic acid (prostaglandin precursor).(Sherwood, Lauralee. Human Physiology : from Cells to Systems.
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Sucrosomial iron is a new oral iron preparation containing ferric pyrophosphate covered by phospholipids plus sucrose ester of fatty acid matrix. This allows the molecule to be absorbed in the gastrointestinal tract by trans-cellular, para-cellular and M-cells independently of hepcidin and due to gastro-resistant properties it does not causes the side effects such as gastric irritation which is commonly associated to oral iron.
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Located with research and manufacturing facilities in Mirjole, (Ratnagiri district) in Maharashtra. In the pharmaceutical segment, VAV Life Sciences’ presence straddles four main therapeutic areas—hepatology, neurology, cardiovascular and oncology. The c-GMP compliant Ratnagiri plant, is equipped to produce lecithin and phospholipids for functional foods, nutritional supplements, novel pharmaceuticals and cosmetics. VAV Life Sciences wins the Business Today SME award 2013 under the Innovation category.
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Scheme of a liposome formed by phospholipids in an aqueous solution Mifamurtide is muramyl tripeptide phosphatidylethanolamine (MTP-PE), a synthetic analogue of muramyl dipeptide. The side chains of the molecule give it a longer elimination half-life than the natural substance. The substance is applied encapsulated into liposomes (L-MTP-PE). Being a phospholipid, it accumulates in the lipid bilayer of the liposomes in the infusion.
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They have a high carbon and hydrogen content and are considerably lacking in oxygen compared to other organic compounds and minerals; they tend to be relatively nonpolar molecules, but may include both polar and nonpolar regions as in the case of phospholipids and steroids.Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter. Molecular Biology of the Cell. New York: Garland Science, 2002, pp.
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Antibodies directed against annexin A5 are found in patients with a disease called the antiphospholipid syndrome (APS), a thrombophilic disease associated with autoantibodies against phospholipid compounds. Annexin A5 forms a shield around negatively charged phospholipid molecules. The formation of an annexin A5 shield blocks the entry of phospholipids into coagulation (clotting) reactions. In the antiphospholipid antibody syndrome, the formation of the shield is disrupted by antibodies.
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By study of connexins still in membranes lipids associated with the connexins have been studied. It was found that specific connexins tended to associate preferentially with specific phospholipids. As formation plaques precede connexins these results still give no certainty as to what is unique about the composition of plaques themselves. Other findings show connexins associate with protein scaffolds used in another junction, the zonula occludens ZO1.
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Kringles are found throughout the blood clotting and fibrinolytic proteins. Kringle domains are believed to play a role in binding mediators (e.g., membranes, other proteins or phospholipids), and in the regulation of proteolytic activity. Kringle domains are characterised by a triple loop, 3-disulfide bridge structure, whose conformation is defined by a number of hydrogen bonds and small pieces of anti-parallel beta-sheet.
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The foundation of all biomembranes consists of a bilayer structure of phospholipids. The phospholipid molecule is amphipathic; it contains a hydrophilic polar head and a hydrophobic nonpolar tail. The phospholipid heads interact with each other and aqueous media, while the hydrocarbon tails orient themselves in the center, away from water. These latter interactions drive the bilayer structure that acts as a barrier for ions and molecules.
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Vesicles can be formed with molecules and ions inside the vesicle by forming the vesicle with the desired molecule or ion present in the solution. Proteins can also be embedded into the membrane through solubilizing the desired proteins in the presence of detergents and attaching them to the phospholipids in which the liposome is formed. These provide researchers with a tool to examine various membrane protein functions.
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Another part of their structure is polar or hydrophilic ("water- loving") and will tend to associate with polar solvents like water. This makes them amphiphilic molecules (having both hydrophobic and hydrophilic portions). In the case of cholesterol, the polar group is a mere –OH (hydroxyl or alcohol). In the case of phospholipids, the polar groups are considerably larger and more polar, as described below.
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Endothelial lipase (LIPG) is a form of lipase secreted by vascular endothelial cells in tissues with high metabolic rates and vascularization, such as the liver, lung, kidney, and thyroid gland. The LIPG enzyme is a vital component to many biological process. These processes include lipoprotein metabolism, cytokine expression, and lipid composition in cells. Unlike the lipases that hydrolyze Triglycerides, endothelial lipase primarily hydrolyzes phospholipids.
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The C2A domain was shown to bind negatively charged phospholipids in a Ca2+-dependent fashion. Ca2+-binding alters the protein-protein interactions of synaptotagmin such as increasing the affinity of synaptotagmin for syntaxin. The C2B domain binds to phosphatidyl-inositol-3,4,5-triphosphate (PIP3) in the absence of calcium ions and to phosphatidylinositol bisphosphate (PIP2) in their presence, suggesting that a lipid-interaction switch occurs during depolarization.
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Phospholipids, such as this glycerophospholipid, have amphipathic character. An amphiphile (from the Greek αμφις, amphis: both and φιλíα, philia: love, friendship) is a chemical compound possessing both hydrophilic (water-loving, polar) and lipophilic (fat-loving) properties. Such a compound is called amphiphilic or amphipathic. This forms the basis for a number of areas of research in chemistry and biochemistry, notably that of lipid polymorphism.
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The protein encoded by this gene is one of at least two lipid transfer proteins found in human plasma. The encoded protein transfers phospholipids from triglyceride-rich lipoproteins to high density lipoprotein (HDL). In addition to regulating the size of HDL particles, this protein may be involved in cholesterol metabolism. At least two transcript variants encoding different isoforms have been found for this gene.
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Bruch's membrane thickens with age, slowing the transport of metabolites. This may lead to the formation of drusen in age-related macular degeneration. There is also a buildup of deposits (Basal Linear Deposits or BLinD and Basal Lamellar Deposits BLamD) on and within the membrane, primarily consisting of phospholipids. The accumulation of lipids appears to be greater in the central fundus than in the periphery.
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Aseptic technique should be used when handling Cleviprex since it contains phospholipids and can support microbial growth. Cleviprex is administered intravenously and should be titrated to achieve the desired blood pressure reduction. Blood pressure and heart rate should be monitored continually during infusion. Cleviprex is a single use product that should not be diluted and should not be administered in the same line as other medications.
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Cleavage sites of phospholipases. Phospholipase C enzymes cut just before the phosphate attached to the R3 moiety. Phospholipase C (PLC) is a class of membrane-associated enzymes that cleave phospholipids just before the phosphate group (see figure). It is most commonly taken to be synonymous with the human forms of this enzyme, which play an important role in eukaryotic cell physiology, in particular signal transduction pathways.
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The composition and characteristics of the cell membrane varies in different cells (plant cells, mammalian cells, bacterial cells, etc). In a membrane bilayer, often the composition of the phospholipids is different between the inner and outer leaflets. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, and sphingomyelin are some of the most common lipids most animal cell membranes. These lipids are widely different in charge, length, and saturation state.
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The protein encoded by this gene belongs to the protein kinase C superfamily. This kinase is activated by Rho family of small G proteins and may mediate the Rho-dependent signaling pathway. This kinase can be activated by phospholipids and by limited proteolysis. The 3-phosphoinositide dependent protein kinase-1 (PDPK1/PDK1) is reported to phosphorylate this kinase, which may mediate insulin signals to the actin cytoskeleton.
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Profilin also binds sequences rich in the amino acid proline in diverse proteins. While most profilin in the cell is bound to actin, profilins have over 50 different binding partners. Many of those are related to actin regulation, but profilin also seems to be involved in activities in the nucleus such as mRNA splicing. Profilin binds some variants of membrane phospholipids (phosphatidylinositol (4,5)-bisphosphate and inositol trisphosphate).
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HRG is also reported to be involved in clearance of apoptotic phagocytes, immune complexes, cell adhesion, migration and angiogenesis, due to its ability to bind various ligands such as phospholipids, fibrinogen, plasminogen, heparin, heparansulfate, tropomysin, and heme, as well as the divalent metal ions zinc, copper, mercury, cadmium and nickel. Mutations in this gene lead to thrombophilia due to abnormal histidine-rich glycoprotein levels.
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Choline is an essential nutrient for humans and many other animals. Choline occurs as a cation that forms various salts (X− in the depicted formula is an undefined counteranion). To maintain health, it must be obtained from the diet as choline or as choline phospholipids, like phosphatidylcholine. Humans and most animals make choline de novo, but production is insufficient in humans and most species.
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Choline and its derivatives have many functions in humans and in other organisms. The most notable function is that choline serves as a synthetic precursor for other essential cell components and signalling molecules, such as phospholipids that form cell membranes, the neurotransmitter acetylcholine, and the osmoregulator trimethylglycine (betaine). Trimethylglycine in turn serves as a source of methyl groups by participating in the biosynthesis of S-adenosylmethionine.
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Fluid mosaic model of a cell membrane The fluid mosaic model explains various observations regarding the structure of functional cell membranes. According to this biological model, there is a lipid bilayer (two molecules thick layer consisting primarily of amphipathic phospholipids) in which protein molecules are embedded. The lipid bilayer gives fluidity and elasticity to the membrane. Small amounts of carbohydrates are also found in the cell membrane.
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They mainly control smooth and vascular muscle dilation. Strength of response is dependent upon the concentration of receptors of target cell and the amount of ligand ( the specific local hormone). Eicosanoids (ī′kō-să-noydz; eicosa = twenty, eidos = formed) are a primary type of local hormone. These local hormones are formed by a chain of 20 amino acids and fatty acids from phospholipids in the cell membrane.
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Retinoids can bind mammalian receptors other than RAR and RXR such as, PPAR, RORb, or COUP-TFII. Furthermore, RXR is sensitive to a wide range of molecules including retinoids, fatty acids, and phospholipids. # Study of steroid receptor evolution revealed that the ancestral steroid receptor could bind a ligand, estradiol. Conversely, the estrogen receptor found in mollusks is constitutively active and did not bind estrogen-related hormones.
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The main components of rice bran wax are aliphatic acids (wax acids) and higher alcohol esters. The aliphatic acids consist of palmitic acid (C16), behenic acid (C22), lignoceric acid (C24), other higher wax acids. The higher alcohol esters consist mainly of ceryl alcohol (C26) and melissyl alcohol (C30). Rice bran wax also contains constituents such as free fatty acids (palmitic acid), squalene and phospholipids.
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This large gathering of materials most likely came from what scientists now call the prebiotic soup. The prebiotic soup refers to the collection of every organic compound that appeared on earth after it was formed. This soup would have most likely contained the compounds necessary to form early cells. Phospholipids are composed of a hydrophilic head on one end, and a hydrophobic tail on the other.
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Dipalmitoylphosphatidylcholine (DPPC) is a phospholipid with two 16-carbon saturated chains and a phosphate group with quaternary amine group attached. The DPPC is the strongest surfactant molecule in the pulmonary surfactant mixture. It also has higher compaction capacity than the other phospholipids, because the apolar tail is less bent. Nevertheless, without the other substances of the pulmonary surfactant mixture, the DPPC's adsorption kinetics is very slow.
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The relationship of bile acids to cholesterol saturation in bile and cholesterol precipitation to produce gallstones has been studied extensively. Gallstones may result from increased saturation of cholesterol or bilirubin, or from bile stasis. Lower concentrations of bile acids or phospholipids in bile reduce cholesterol solubility and lead to microcrystal formation. Oral therapy with chenodeoxycholic acid and/or ursodeoxycholic acid has been used to dissolve cholesterol gallstones.
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Interactions between hydrophobic amino-acid residues and the adjacent membranes cause destabilization of the membranes. This allows the phospholipids in the outer layer of each membrane to interact with each other. The outer leaflets of the two membranes form a hemifusion stalk to minimize energetically unfavorable interactions between hydrophobic phospholipid tails and the environment. This stalk expands, allowing the inner leaflets of each membrane to interact.
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Given that snake venom contains many biologically active ingredients, some may be useful to treat disease. For instance, phospholipases type A2 (PLA2s) from the Tunisian vipers Cerastes cerastes and Macrovipera lebetina have been found to have antitumor activity. Anticancer activity has been also reported for other compounds in snake venom. PLA2s hydrolyze phospholipids, thus could act on bacterial cell surfaces, providing novel antimicrobial (antibiotic) activities.
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Lung surfactant (LS) is a surface-active material produced by most air-breathing animals for the purpose of reducing the surface tension of the water layer where gas exchange occurs in the lungs, given that the movements due to inhalation and exhalation may cause damage if there is not enough energy to sustain alveolar structural integrity. The monolayer formed by the LS on the interface is composed primarily of phospholipids (80%), in addition to proteins (12%) and neutral lipids (8%). Among the phospholipids, the most prevalent one is phosphatidylcholine (PC, or lecithin) (70–85%), which in turn is the basis of a pool of similar diacylphophatidylcholines of which 50% is dipalmitoylphosphatidylcholine or DPPC. While DPPC itself already has the ability to reduce the surface tension of the alveolar liquid, the proteins and other lipids in the surfactant further facilitate the adsorption of oxygen into the air-liquid interface.
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The C-terminal C2-like PLAT domain binds calcium and allows the toxin to bind to the phospholipid head-groups on the cell surface. The C-terminal domain enters the phospholipid bilayer. The N-terminal domain has phospholipase activity. This property allows hydrolysis of phospholipids such as phosphatidyl choline, mimicking endogenous phospholipase C. The hydrolysis of phosphatidyl choline produces diacylglycerol, which activates a variety of second messenger pathways.
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2007 Oct;1(1):5-23Bikov A, Gajdocsy R, Huszar E, Szili B, Lazar Z, Antus B, Losonczy G, Horvath I. Exercise increases exhaled breath condensate cysteinyl leukotriene concentration in asthmatic patients. JOURNAL OF ASTHMA 47:(9) pp. 1057-1062. (2010) and macromolecules such as mucin, phospholipids and DNA.Jackson AS, Sandrini A, Campbell C, Chow S, Thomas PS, Yates DH. Comparison of Biomarkers in Exhaled Breath Condensate and Bronchoalveolar Lavage.
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In addition, other AGC kinases, such as D6PK, phosphorylate and activate PIN transporters. AGC kinases, including PINOID and D6PK, target to the plasma membrane via binding to phospholipids. Upstream of D6PK, 3'-phosphoinositide dependent protein kinase 1 (PDK1) acts as a master regulator. PDK1 phosphorylates and activates D6PK at the basal side of plasma membrane, executing the activity of PIN-mediated polar auxin transport and subsequent plant development.
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The synthesis of the phospholipids contained in pulmonary surfactant takes place in the endoplasmic reticulum of type II pneumocytes. Pulmonary surfactant has both protein and lipid components. More specifically, it has been found that phosphatidylcholine (PC) is the most abundant phospholipid (70%–85%), and that PC is primarily present as dipalmitoylphosphatidylcholine (DPPC). De novo synthesis of phosphatidylcholine in the lung arises primarily from cytidine diphosphate-choline (CDP-choline).
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The main function of beta-ketoacyl-ACP synthase is to produce fatty acids of various lengths for use by the organism. These uses include energy storage and creation of cell membranes. Fatty acids can also be used to synthesize prostaglandins, phospholipids, and vitamins, among many other things. Further, palmitic acid, which is created by the beta-ketoacyl-synthases on type I FAS, is used in a number of biological capacities.
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Due to this role, an imbalance in the concentrations of lysophosphatidic acid phosphatase can frequently lead to several metabolic diseases. Lysophosphatidic acid phosphatase is also responsible for the digestion of lysophosphatidic acids when the cell enters a state of phosphate starvation. These enzymes break down LPAs and release phosphate groups. This stops the production of phospholipids and phosphatidic acids to signal the end of a cell's proliferation process.
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In those patients, there was also a markedly high rate of citrate synthase. The second phenotype presented with similar clinical symptoms, but no strokes. As phosphatidic acid is also involved in the synthesis of phospholipids, its loss will result in changes to the lipid composition of the inner mitochondrial membrane. These effects manifest as cataract formation in the eye, respiratory chain dysfunction and cardiac hypertrophy in heart tissue.
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Animal fats are complex mixtures of triglycerides, with lesser amounts of both the phospholipids and cholesterol molecules from which all animal (and human) cell membranes are constructed. Since all animal cells manufacture cholesterol, all animal-based foods contain cholesterol in varying amounts. Major dietary sources of cholesterol include red meat, egg yolks and whole eggs, liver, kidney, giblets, fish oil, and butter. Human breast milk also contains significant quantities of cholesterol.
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Thudichum discovered in human brain some phospholipids (cephalin), glycolipids (cerebroside) and sphingolipids (sphingomyelin). The terms lipoid, lipin, lipide and lipid have been used with varied meanings from author to author. In 1912, Rosenbloom and Gies proposed the substitution of "lipoid" by "lipin". In 1920, Bloor introduced a new classification for "lipoids": simple lipoids (greases and waxes), compound lipoids (phospholipoids and glycolipoids), and the derived lipoids (fatty acids, alcohols, sterols).
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C2A in otoferlin's longer form with six C2 domains is structurally similar to dysferlin C2A. However, the loop 1 in calcium binding site of otoferlin C2A is significantly shorter than the homologous loop in dysferlin and myoferlin C2A domains. Therefore, it is unable to bind to calcium. Otoferlin C2A is also unable to bind to phospholipids and hence it is structurally and functionally different from other C2 domains.
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Churning cream into butter using a hand-held mixer. Unhomogenized milk and cream contain butterfat in microscopic globules. These globules are surrounded by membranes made of phospholipids (fatty acid emulsifiers) and proteins, which prevent the fat in milk from pooling together into a single mass. Butter is produced by agitating cream, which damages these membranes and allows the milk fats to conjoin, separating from the other parts of the cream.
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Studies have shown significant increase in the levels of plasma glucose, phospholipids, nitrite and nitrate, and lipidperoxides with a decrease in plasma cholesterol. It is also shown that inhaling d-trans-Allethrin can irritate the nose, throat and lungs. High exposure may cause headache, dizziness, irritability, seizures, and a loss of consciousness. Exposure may also cause a skin allergy or asthma-like allergy, and damage the liver and kidneys.
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They are a subclass of eicosanoids and form the prostanoid class of fatty acid derivatives. The prostaglandins are synthesized in the cell membrane by the cleavage of arachidonate from the phospholipids that make up the membrane. This is catalyzed either by phospholipase A2 acting directly on a membrane phospholipid, or by a lipase acting on DAG (diacyl-glycerol). The arachidonate is then acted upon by the cyclooxygenase component of prostaglandin synthase.
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A number of preclinical studies have been conducted using MFGM and combinations of MFGM-derived components. Liu et al. (2014) studied brain development and spatial learning and memory in neonatal piglets. Piglets that were fed with a formula containing milk phospholipids and gangliosides to mimic levels in human milk made choices more rapidly and with fewer errors in a spatial T-maze cognitive test compared to controls, implying improved spatial learning.
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The three main structures phospholipids form in solution; the liposome (a closed bilayer), the micelle and the bilayer. Self-assembled vesicles are essential components of primitive cells. The second law of thermodynamics requires that the universe move in a direction in which disorder (or entropy) increases, yet life is distinguished by its great degree of organization. Therefore, a boundary is needed to separate life processes from non-living matter.
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After its synthesis, cardiolipin cannot exert its proper functions until it is actively remodeled. Tafazzin, an acyl-specific transferase, catalyzes the acyl transfer reaction between phospholipids and lysophospholipids in a CoA- independent manner. The remodeling process of cardiolipin involves reaching a final acyl composition that is primarily linoleoyl residues. TAZ interacts with an immature cardiolipin by adding the fatty acid linoleic acid, which catalyzes the remodeling of the cardiolipin.
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The activity of phospholipase D is extensively regulated by hormones, neurotransmitters, lipids, small monomeric GTPases, and other small molecules that bind to their corresponding domains on the enzyme. In most cases, signal transduction is mediated through production of phosphatidic acid, which functions as a secondary messenger. Specific phospholipids are regulators of PLD activity in plant and animal cells. Most PLDs require phosphatidylinositol 4,5-bisphosphate (PIP2), as a cofactors for activity.
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Blocks of similar length form layers (often called lamellae in the technical literature). Between the cylindrical and lamellar phase is the gyroid phase. The nanoscale structures created from block copolymers could potentially be used for creating devices for use in computer memory, nanoscale-templating and nanoscale separations. Block copolymers are sometimes used as a replacement for phospholipids in model lipid bilayers and liposomes for their superior stability and tunability.
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Delta toxin is quite heat-stable, unlike S. aureus alpha and beta toxins. However, the addition of lecithin specifically prevents delta toxin from lysing cells. Delta toxin activity can also both enhanced and prevented with saturated, straight-chain fatty acids of varying lengths. Phospholipids 13 to 19 carbons in length enhanced the lytic activity of delta toxin, whereas those that were 21 to 23 carbons long were inhibitory.
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There are several examples of molecules that present amphiphilic properties: Hydrocarbon-based surfactants are an example group of amphiphilic compounds. Their polar region can be either ionic, or non-ionic. Some typical members of this group are: sodium dodecyl sulfate (anionic), benzalkonium chloride (cationic), cocamidopropyl betaine (zwitterionic), and 1-octanol (long-chain alcohol, non- ionic). Many biological compounds are amphiphilic: phospholipids, cholesterol, glycolipids, fatty acids, bile acids, saponins, local anaesthetics, etc.
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Electrical pulses are also used to intracellularly deliver siRNA into cells. The cell membrane is made of phospholipids which makes it susceptible to an electric field. When quick but powerful electrical pulses are initiated the lipid molecules reorient themselves, while undergoing thermal phase transitions because of heating. This results in the making of hydrophilic pores and localized perturbations in the lipid bilayer cell membrane also causing a temporary loss of semipermeability.
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PDPK1 stands for 3- _p_ hosphoinositide- _d_ ependent _p_ rotein _k_ inase _1_. PDPK1 functions downstream of PI3K through PDPK1's interaction with membrane phospholipids including phosphatidylinositols, phosphatidylinositol (3,4)-bisphosphate and phosphatidylinositol (3,4,5)-trisphosphate. PI3K indirectly regulates PDPK1 by phosphorylating phosphatidylinositols which in turn generates phosphatidylinositol (3,4)-bisphosphate and phosphatidylinositol (3,4,5)-trisphosphate. However, PDPK1 is believed to be constitutively active and does not always require phosphatidylinositols for its activities.
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The major membrane lipids PtdCho - Phosphatidylcholine; PtdEtn - Phosphatidylethanolamine; PtdIns - Phosphatidylinositol; PtdSer - Phosphatidylserine. Membrane lipids are a group of compounds (structurally similar to fats and oils) which form the double- layered surface of all cells (lipid bilayer). The three major classes of membrane lipids are phospholipids, glycolipids, and cholesterol. Lipids are amphiphilic: they have one end that is soluble in water ('polar') and an ending that is soluble in fat ('nonpolar').
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The remaining protein C zymogen comprises slightly modified forms of the protein. Activation of the enzyme occurs when a thrombin molecule cleaves away the activation peptide from the N-terminus of the heavy chain. The active site contains a catalytic triad typical of serine proteases (His253, Asp299 and Ser402). The Gla domain is particularly useful for binding to negatively charged phospholipids for anticoagulation and to EPCR for cytoprotection.
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Sulfolobus metallicus could be used for mass-producing archeal phospholipids. These lipids have promising applications in drug delivery by acting as liposomes, or they can be used as lubricants but can be expensive to synthesize. Sulfolobus metallicus can potentially be used to provide a cheaper way to synthesize these lipids. If Sulfolobus metallicus is used as a bioleacher on the industrial scale, it grows in volume in tons per day.
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This membrane enzyme forms homodimers, partly separated by an internal ∼9-Å-wide channel. The metallo beta-lactamase protein fold is adapted to associate with membrane phospholipids. A hydrophobic cavity provides an entry way for the substrate NAPE into the active site, where a binuclear zinc center catalyzes its hydrolysis. Bile acids bind with high affinity to selective pockets in this cavity, enhancing dimer assembly and enabling catalysis.
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All G protein α sub-units contain palmitate, which is a 16-carbon saturated fatty acid, that is attached near the N-terminus through a labile, reversible thioester linkage to a cysteine amino acid. It is this palmitoylation that allows the G protein to interact with membrane phospholipids due to the hydrophobic nature of the alpha sub-units. The gamma sub-unit is also lipid modified and can attach to the plasma membrane as well.
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The basis for the defect in PS translocation is, at present, unknown. A candidate protein, scramblase,Sims PJ, Wiedmer T. Unraveling the mysteries of phospholipid scrambling. Thromb Haemost 2001; 86:266-275 that may be involved in this process appears to be normal in Scott syndrome platelets.Zhou Q, Sims PJ, Wiedmer T. Expression of proteins controlling transbilayer movement of plasma membrane phospholipids in the B lymphocytes from a patient with Scott syndrome.
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This protein is a member of the MDR/TAP subfamily. Members of the MDR/TAP subfamily are involved in multidrug resistance as well as antigen presentation. The function of this half-transporter has not yet been determined; however, it may involve the compartmentalization and transport of heme, as well as peptides, from the mitochondria to the nucleus and cytosol. This protein may also play a role in the transport of phospholipids into mitochondrial membranes.
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While initially studied as a cancer medication, due to side effects it was never used for this purpose. Phospholipid group alkylphosphocholine were known since the early 1980s, particularly in terms of their binding affinity with cobra venom. In 1987 the phospholipids were found to be potent toxins on leukemic cell culture. Initial in vivo investigation on the antineoplastic activity showed positive result, but then only at high dosage and at high toxicity.
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Glycerol is a precursor for synthesis of triacylglycerols and of phospholipids in the liver and adipose tissue. When the body uses stored fat as a source of energy, glycerol and fatty acids are released into the bloodstream. Glycerol is mainly metabolized in the liver. Glycerol injections can be used as a simple test for liver damage, as its rate of absorption by the liver is considered an accurate measure of liver health.
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ENPP7 is fully developed in the intestine before birth, which gives the infant ability to digest sphingomyelin in the milk. The daily intake of sphingomyelin for human with Western diet is about 300 mg. Under physiological conditions, only part of the sphingomyelin can be digested and absorbed. The limitation is thought to be caused by several factors that are present in the intestine such as cholesterol, phospholipids, fat and high concentrations of bile salts.
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When PA activates the channel, PIP2 blocks the effect of PA inhibiting the channels. Ethanol When ethanol is consumed, phospholipase D incorporates the ethanol into phospholipids generating the unnatural and long lived lipid phosphatidylethanol(PEth) in a process called transphoshatidylation. The PEth competes with PA and the competition antagonizes TREK-1 channels. The competition of PEth on potassium channel is thought to contribute to the anesthetic effect of ethanol and perhaps hangover.
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WD40 repeat proteins are key components of many essential biologic functions. They regulate the assembly of multiprotein complexes by presenting a beta-propeller platform for simultaneous and reversible protein-protein interactions. Members of the WIPI subfamily of WD40 repeat proteins, such as WIPI2, have a 7-bladed propeller structure and contain a conserved motif for interaction with phospholipids. WIPI2 is the mammalian homolog of Atg18, not Atg21, along with the closely related protein, WIPI1.
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The hydrophilic region contains the polar head group. This region is exposed to aqueous substances located mainly in the exterior portion of the biomembrane. The hydrophilic region consists of the non-polar acyl chains or fatty acids groups facing the interior of the biomembrane. Phospholipids consist of two non-polar hydrocarbon chains with ester or ether bonds to the phosphate group which is also linked by ester or ether bonds to the polar hydrophilic region.
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Yeagle, Philip. The Structure of Biological Membranes. 2nd. ed. CRC Press, (2005). 173–194. For example, the strength of the intermolecular forces within the biomembrane are fairly strong but when lipids are extracted from biomembranes for analytical purposes there is a decrease in the constraints by the intermolecular forces against the phospholipids which may cause the lipid to undergo polymorphism as well as a temporary rearrangement of other lipids or proteins in the biomembrane.
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Superparamagnetic iron–platinum particles (SIPPs) have been reported and had significantly better T2 relaxivities compared with the more common iron oxide nanoparticles. SIPPs were also encapsulated with phospholipids to create multifunctional SIPP stealth immunomicelles that specifically targeted human prostate cancer cells. These are, however, investigational agents which have not yet been tried in humans. In a recent study, multifunctional SIPP micelles were synthesized and conjugated to a monoclonal antibody against prostate-specific membrane antigen.
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Bacteria such as Legionella pneumophila utilize phospholipase A2 end- products (fatty acids and lysophospholipids) to cause host cell (macrophage) apoptosis through cytochrome C release. LPCs are present as minor phospholipids in the cell membrane (≤ 3%) and in the blood plasma (8–12%). Since LPCs are quickly metabolized by lysophospholipase and LPC- acyltransferase, they last only shortly in vivo. By replacing the acyl-group within the LPC with an alkyl-group, alkyl-lysophospholipids (ALP) were synthesized.
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These are all energy- requiring processes. Under physiologic conditions, the plasma membrane of cells has an asymmetric distribution of phospholipids. aminophospholipids, phosphatidylserine, and phosphatidylethanolamine are specifically sequestered in the inner leaflet of the membrane. The transbilayer lipid distribution is under the control of three phospholipidic pumps: an inward-directed pump, or flippase; an outward-directed pump, or floppase; and a lipid scramblase, responsible for non-specific redistribution of lipids across the membrane.
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These shortening pathways also are likely to serve in inactivating 20-HETE, although the initial product of this shortening pathway, 20-carboxy-HETE, dilates coronary microvessels in the pig heart and thereby could serve to antagonize the vasoconstrictor actions of 20-HETE, at least in this organ and species. Coronary artery endothelial cells isolated from pigs incorporate 20-HETE primarily into the sn-2 position of phospholipids through a coenzyme A-dependent process.
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Vitamin K has been found to be associated with sulfatide. Not only in animals, but also in bacteria, vitamin K has been observed to influence sulfatide concentrations in the brain. Vitamin K in the nervous system is responsible for the activation of enzymes that are essential for the biosynthesis of brain phospholipids, such as sulfatide. When warfarin, a vitamin K antagonist, is added to an animal model system, sulfatide synthesis is impaired.
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Members of the genus are not characterized chemotaxonomically by type III/B cell walls (meso-diaminopimelic acid and madurose are present) with peptidoglycan structures of the acetyl type. The predominant menaquinone types are MK-9(H4), MK-9(H6) and MK-9(H8). The phospholipid pattern is PI (diphosphatidylglycerol and phosphatidylinositol are present as major phospholipids) and the fatty acid pattern is type 3a (branched saturated and unsaturated fatty acids plus tuberculostearic acid).
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The Lurpak brand of butter and spreads is owned by the Danish Dairy Board, and Castello is a cheese brand including blue cheese and yellow cheeses. Arla Foods incorporates Arla Foods Ingredients, a former division established as an independent subsidiary in 2011. The company develops and manufactures milk based ingredients, primarily functional and nutritional milk proteins, bioactive phospholipids, minerals, permeate and lactose for the food industry. The head office is located in Denmark.
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Cells are immersed in a medium where access to nutrients is limited to synthetically modified analogues of standard fuels such as sugars. As a consequence, these altered biomolecules are incorporated into the cells in the same manner as the unmodified metabolites. A probe is then incorporated into the system to image the fate of the altered biomolecules. Other methods of functionalization include enzymatically inserting azides into proteins, and synthesizing phospholipids conjugated to cyclooctynes.
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The PEMT enzyme converts phosphatidylethanolamine (PE) to phosphatidylcholine (PC) via three sequential methylations by S-adenosyl methionine (SAM). The enzyme is found in endoplasmic reticulum and mitochondria-associated membranes. It accounts for ~30% of PC biosynthesis, with the CDP-choline, or Kennedy, pathway making ~70%. PC, typically the most abundant phospholipid in animals and plants, accounts for more than half of cell membrane phospholipids and approximately 30% of all cellular lipid content.
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The biliary tract, (biliary tree or biliary system) refers to the liver, gall bladder and bile ducts, and how they work together to make, store and secrete bile. Bile consists of water, electrolytes, bile acids, cholesterol, phospholipids and conjugated bilirubin. Some components are synthesised by hepatocytes (liver cells), the rest are extracted from the blood by the liver. Bile is secreted by the liver into small ducts that join to form the common hepatic duct.
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Antiphospholipid syndrome is an autoimmune disease, in which "antiphospholipid antibodies" (anticardiolipin antibodies and lupus anticoagulant) react against proteins that bind to anionic phospholipids on plasma membranes. Like many autoimmune diseases, it is more common in women than in men. The exact cause is not known, but activation of the system of coagulation is evident. Clinically important antiphospholipid antibodies (those that arise as a result of the autoimmune process) are associated with thrombosis and vascular disease.
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Among their physiological substrates, human and rodent AlOX15 enzymes act on linoleic acid, alpha-linolenic acid, gamma-linolenic acid, arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid when presented not only as free acids but also when incorporated as esters in phospholipids, glycerides, or Cholesteryl esters. The human enzyme is particularly active on linoleic acid, preferring it over arachidonic acid. It is less active on PUFA that are esters within the cited lipids.
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Omega−3 fatty acids occur naturally in two forms, triglycerides and phospholipids. In the triglycerides, they, together with other fatty acids, are bonded to glycerol; three fatty acids are attached to glycerol. Phospholipid omega−3 is composed of two fatty acids attached to a phosphate group via glycerol. The triglycerides can be converted to the free fatty acid or to methyl or ethyl esters, and the individual esters of omega−3 fatty acids are available.
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The HDV (hepatitis delta virus) is a small, spherical virus with a 36 nm diameter. It has an viral envelope containing host phospholipids and three kinds of HBV envelope protein – large, medium, and small hepatitis B surface antigens; this surrounds an inner nucleocapsid. The nucleocapsid contains the genome surrounded by about 200 molecules of hepatitis D antigen (HDAg) for each genome. The central region of HDAg has been shown to bind RNA.
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The term lipid comprises a diverse range of molecules and to some extent is a catchall for relatively water-insoluble or nonpolar compounds of biological origin, including waxes, fatty acids (including essential fatty acids), fatty-acid derived phospholipids, sphingolipids, glycolipids and terpenoids, such as retinoids and steroids. Some lipids are linear aliphatic molecules, while others have ring structures. Some are aromatic, while others are not. Some are flexible, while others are rigid.
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Scheme of a liposome formed by phospholipids in an aqueous solution. In cell biology, a vesicle is a structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer. Vesicles form naturally during the processes of secretion (exocytosis), uptake (endocytosis) and transport of materials within the plasma membrane. Alternatively, they may be prepared artificially, in which case they are called liposomes (not to be confused with lysosomes).
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When phospholipids are exposed to water, they self-assemble into a two-layered sheet with the hydrophobic tails pointing toward the center of the sheet. This arrangement results in two “leaflets” that are each a single molecular layer. The center of this bilayer contains almost no water and excludes molecules like sugars or salts that dissolve in water. The assembly process is driven by interactions between hydrophobic molecules (also called the hydrophobic effect).
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Archaeol in the sediments typically originates from the hydrolysis of archaea membrane phospholipids during diagenesis. Due to its high preservation potential, it is often detected and used by organic geochemists as a biomarker for archaea activity, especially for methanogen biomass and activity. As a methanogen proxy, it is used by Michinari Sunamura et al. to directly measure the methanogens in the sediments of Tokyo Bay, and also used by Katie L. H. Lim et al.
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Whereas mantle dentin forms from the preexisting ground substance of the dental papilla, primary dentin forms through a different process. Odontoblasts increase in size, eliminating the availability of any extracellular resources to contribute to an organic matrix for mineralization. Additionally, the larger odontoblasts cause collagen to be secreted in smaller amounts, which results in more tightly arranged, heterogeneous nucleation that is used for mineralization. Other materials (such as lipids, phosphoproteins, and phospholipids) are also secreted.
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A smaller mean cellular volume recorded in free living flamingos coupled with similar mean hemoglobin content between captive and free living flamingos could show different oxygen diffusion characteristics between these two groups. Plasma chemistry remains relatively stable with age but lower values of protein content, uric acid, cholesterol, triglycerides, and phospholipids were seen in free living flamingos. This trend can be attributed to shortages and variances in food intake in free living flamingos.
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Multiple lung diseases, like ISD or RDS, in newborns and late-onsets cases have been linked to dysfunction of surfactant metabolism. Surfactant is a mixture of 90% phospholipids and 10% other proteins, produced by epithelial type II cells in the alveolar. This mixture is made and packaged into lysosomally- derived structures called lamellar bodies. Lamellar bodies are then secreted into the liquid-air interphase surface of alveolar through membrane fusion initiated by influx of Ca2+.
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This gene encodes a member of the phospholipase C family, which catalyze the hydrolysis of phosphatidylinositol 4,5-bisphosphate to generate the second messengers diacylglycerol and inositol 1,4,5-trisphosphate (IP3). Diacylglycerol and IP3 mediate a variety of cellular responses to extracellular stimuli by inducing protein kinase C and increasing cytosolic Ca2+ concentrations. This enzyme localizes to the plasma membrane and requires calcium for activation. Its activity is inhibited by spermine, sphingosine, and several phospholipids.
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In 2014 Enzymotec settled litigation with Canada-based Neptune Technologies & Bioressources over patents held by Neptune related to phospholipids like omega-3 oil extracted from krill oil. In 2015 shareholders filed a class action securities fraud case against Enzymotec over the IPO prospectus, claiming that the company's management had misrepresented its future profitability and the regulatory status of its products in China; most claims in the suit survived a motion to dismiss in December 2015.
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Neohemocyte ("new blood cell") is the name given by its University of California at San Francisco creators to artificial red blood cells. These cells are created by packing natural hemoglobin molecules in fat bubbles made from phospholipids and cholesterol, resulting in cells roughly one-twelfth the size of human erythrocytes. They provide an advantage over real blood cells in their longer storage capacity (about six months versus 35 days).Marieb, Elaine Nicpon.
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Keller studies the organization of lipids in membranes. Cell membranes are composed of lipids and proteins. Her early work "Separation of liquid phases in giant vesicles of ternary mixtures of phospholipids and cholesterol" used fluorescence microscopy to observe a mixture of saturated and unsaturated lipids and observed microscopic separations of two coexisting liquid phases—miscibility transition. Her works contributed to models of protein aggregation within membranes and the theory of membrane lateral pressure.
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He left Germany and moved to England, arriving on 2 April 1933 with £10 in his pocket. Geneticist and physiologist J.B.S. Haldane helped him obtain a position at University College Hospital, London. After a couple of months he was accepted as a PhD student at Fitzwilliam House, Cambridge University, where he began working on phospholipids under the direction of Sir Frederick Gowland Hopkins. In 1935, he accepted a job at Oxford University as a lecturer in pathology.
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Like nitrogen, phosphorus is involved with many vital plant processes. Within a plant, it is present mainly as a structural component of the nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), as well as a constituent of fatty phospholipids, that are important in membrane development and function. It is present in both organic and inorganic forms, both of which are readily translocated within the plant. All energy transfers in the cell are critically dependent on phosphorus.
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Names of acyl groups of amino acids are formed by the replacement of the ending -ine by the ending -yl. For example, the acyl group of glycine is glycyl, and of lysine is lysyl. Names of acyl groups of ribonucleoside monophosphates such as AMP (5′-adenylic acid), GMP (5′-guanylic acid), CMP (5′-cytidylic acid), and UMP (5′-uridylic acid) are adenylyl, guanylyl, cytidylyl, and uridylyl respectively. In phospholipids, the acyl group of phosphatidic acid is called phosphatidyl-.
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Most of the fat found in food is in the form of triglycerides, cholesterol, and phospholipids. Some dietary fat is necessary to facilitate absorption of fat-soluble vitamins (A, D, E, and K) and carotenoids.Bhagavan, p. 903. Humans and other mammals have a dietary requirement for certain essential fatty acids, such as linoleic acid (an omega-6 fatty acid) and alpha-linolenic acid (an omega-3 fatty acid) because they cannot be synthesized from simple precursors in the diet.
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The properties of the supercritical fluid can be altered by varying the pressure and temperature, allowing selective extraction. For example, volatile oils can be extracted from a plant with low pressures (100 bar), whereas liquid extraction would also remove lipids. Lipids can be removed using pure CO2 at higher pressures, and then phospholipids can be removed by adding ethanol to the solvent. The same principle can be used to extract polyphenols and unsaturated fatty acids separately from wine wastes.
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Ions cannot passively diffuse through the gastrointestinal tract because the epithelial cell membrane is made up of a phospholipid bilayer. The bilayer is made up of two layers of phospholipids in which the charged hydrophilic heads face outwards and the non-charged hydrophobic fatty acid chains are in the middle of the layer. The uncharged fatty acid chains repel ionized, charged molecules. This means that the ionized molecules cannot pass through the intestinal membrane and be absorbed.
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The proposed mechanism, is that low levels of folate or vitamin B12 can disrupt transmethylation reaction, leading to an accumulation of homocysteine (hyperhomocysteinemia) and to impaired metabolism of neurotransmitters (especially the hydroxylation of dopamine and serotonin from tyrosine and tryptophan), phospholipids, myelin, and receptors. High homocysteine levels in the blood can lead to vascular injuries by oxidative mechanisms which can contribute to cerebral dysfunction. All of these can lead to the development of various disorders, including depression.
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Apolipoproteins are proteins that bind lipids (oil-soluble substances such as fat and cholesterol) to form lipoproteins. They transport lipids (and fat soluble vitamins) in blood, cerebrospinal fluid and lymph. The lipid components of lipoproteins are insoluble in water. However, because of their detergent-like (amphipathic) properties, apolipoproteins and other amphipathic molecules (such as phospholipids) can surround the lipids, creating a lipoprotein particle that is itself water-soluble, and can thus be carried through water-based circulation (i.e.
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Since its implementation, SIESTA has become quite popular, being increasingly used by researchers in geosciences, biology, and engineering (apart from those in its natural habitat of materials physics and chemistry) and has been applied to a large variety of systems including surfaces, adsorbates, nanotubes, nanoclusters, biological molecules, amorphous semiconductors, ferroelectric films, low-dimensional metals, etc.Mashaghi A et al. Hydration strongly affects the molecular and electronic structure of membrane phospholipids J. Chem. Phys. 136, 114709 (2012) Mashaghi A et al.
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MFGM lipid components such as sphingolipids are involved in the intestinal uptake of cholesterol. Studies in adult rodents have shown that milk sphingomyelin could lower the intestinal absorption of cholesterol in a dose-dependent manner. Intestinal cholesterol absorption in adult rodents consuming a high fat diet was limited by sphingomyelin supplementation. Milk sphingomyelin and other phospholipids with high affinity for cholesterol could limit the micellar solubility of intestinal cholesterol, thereby limiting the cholesterol uptake by the enterocyte.
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1-Oleoyl-2-palmitoyl-phosphatidylcholine Phosphatidylcholines (PC) are a class of phospholipids that incorporate choline as a headgroup. They are a major component of biological membranes and can be easily obtained from a variety of readily available sources, such as egg yolk or soybeans, from which they are mechanically or chemically extracted using hexane. They are also a member of the lecithin group of yellow-brownish fatty substances occurring in animal and plant tissues. Dipalmitoyl phosphatidylcholine (a.k.a.
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An unhealthy or malnourished cell will get stuck at this checkpoint. The G2/M checkpoint is where the cell ensures that it has enough cytoplasm and phospholipids for two daughter cells. But sometimes more importantly, it checks to see if it is the right time to replicate. There are some situations where many cells need to all replicate simultaneously (for example, a growing embryo should have a symmetric cell distribution until it reaches the mid- blastula transition).
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August first worked in the catalytic synthesis of fatty acids and other lipids as an undergraduate student in Prof. Dea's laboratory at California State University, Los Angeles. This work resulted in the publication on methods to easily catalyze the insertion of deuterium into unsaturated fatty acids, which could then be used as probes of membrane structure.A. August, C.J. Dao, D. Jensen, Q. Zhang, and P.Dea. “A facile catalytic deuteration of unsaturated fatty acids and phospholipids.” (1993) Microchem.
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Specialized cells can have a lot of smooth endoplasmic reticulum and in these cells the smooth ER has many functions. It synthesizes lipids, phospholipids, and steroids. Cells which secrete these products, such as those in the testes, ovaries, and sebaceous glands have an abundance of smooth endoplasmic reticulum. It also carries out the metabolism of carbohydrates, detoxification of natural metabolism products and of alcohol and drugs, attachment of receptors on cell membrane proteins, and steroid metabolism.
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Surfactant is synthesised by type II alveolar cells and is made of a complex of phospholipids, proteins and saccharides. It functions to lower surface tension (to allow for lung expansion during inspiration), stabilise alveoli at the end of expiration (to prevent alveolar collapse) and prevents lung oedema. Surfactant also contributes to lung protection and defence as it is also an anti-inflammatory agent. Surfactant enhances the removal of inhaled particles and senescent cells away from the alveolar structure.
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The Ceragenins have been the subject of in vitro analysis and have demonstrated a range of action against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Staphylococcus aureus (VRSA), tobramycin-resistant Pseudomonas aeruginosa (PATR), Escherichia coli, vaccinia virus, HIV, and Bacillus anthracis (anthrax) among others. The compounds work by breaching the outer membranes of their targets. The compounds are positively charged and are electrostatically attracted to the negatively charged phospholipids that tend to distinguish prokaryotic from eukaryotic cells.
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N-Acylphosphatidylethanolamines are also an important intermediaries in the biosynthesis of endocannabinoids. NAPEs are formed from phosphatidylethanolamines, a group of cell membrane phospholipids characteristic of nervous tissue. After being cleaved by phospholipases, NAPEs can be transformed into N-acylethanolamines, including the endocannabinoid anandamide. While NAPE-PLD is the enzyme responsible for catalyzing said release of N-acylethanolamine (NAE) from N-acyl-phosphatidylethanolamine (NAPE), this specific subtype of phospholipase D is not responsible for the formation of the anandamide.
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Acetylcholine is used by organisms in all domains of life for a variety of purposes. It is believed that choline, a precursor to acetylcholine, was used by single celled organisms billions of years ago for synthesizing cell membrane phospholipids. Following the evolution of choline transporters, the abundance of intracellular choline paved the way for choline to become incorporated into other synthetic pathways, including acetylcholine production. Acetylcholine is used by bacteria, fungi, and a variety of other animals.
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The Framingham Heart Study and other epidemiological studies have found a correlation between lipoproteins and cardiovascular disease.Therapeutic lipidology, p. vii-viii A class of lipids known as phospholipids help make up what is known as lipoproteins, and a type of lipoprotein is called high density lipoprotein (HDL). A high concentration of high density lipoproteins-cholesterols (HDL-C) have what is known as a vasoprotective effect on the body, a finding that correlates with an enhanced cardiovascular effect.
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P-ATPases (sometime known as E1-E2 ATPases) are found in bacteria and also in eukaryotic plasma membranes and organelles. Its name is due to short time attachment of inorganic phosphate at the aspartate residues at the time of activation. Function of P-ATPase is to transport a variety of different compounds, like ions and phospholipids, across a membrane using ATP hydrolysis for energy. There are many different classes of P-ATPases, which transports a specific type of ion.
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Choline is often not classified as a vitamin, but as a nutrient with an amino acid–like metabolism. In most animals, choline phospholipids are necessary components in cell membranes, in the membranes of cell organelles, and in very low-density lipoproteins. Choline is required to produce acetylcholine - a neurotransmitter - and S-adenosylmethionine, a universal methyl donor involved in the synthesis of homocysteine. Symptomatic choline deficiency - rare in humans - causes nonalcoholic fatty liver disease and muscle damage.
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Lipophagy is the degradation of lipids by autophagy, a function which has been shown to exist in both animal and fungal cells. The role of lipophagy in plant cells, however, remains elusive. In lipophagy the target are lipid structures called lipid droplets (LDs), spheric "organelles" with a core of mainly triacylglycerols (TAGs) and a unilayer of phospholipids and membrane proteins. In animal cells the main lipophagic pathway is via the engulfment of LDs by the phagophore, macroautophagy.
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Antinuclear antibodies cause an inflammation in the uterus that does not allow it to be a suitable host for implantation of the embryo. Natural killer cells misinterpret the fetal cells as cancer cells and attack them. An individual that presents with reproductive autoimmune failure syndrome has unexplained infertility, endometriosis, and repetitive miscarriages due to elevated levels of antinuclear antibodies circulating. Both the presence of anti-phospholipids antibodies and antinuclear antibodies have toxic effects on the implantation of embryos.
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Krill oil and oceanic fish oil are rich in omega-3 fatty acids, mainly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). While both contain some EPA and DHA as free fatty acids, krill oil contains particularly rich amounts of choline-containing phospholipids and a phosphatidylcholine concentration of 34 grams per 100 grams of oil. Krill oil also contains appreciable content of astaxanthin at 0.1 to 1.5 mg/mL depending on processing methods, and is responsible for its red color.
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The practical uses of an instrument that uses a single probe are that it allows for the developing of a high throughput device. A high throughput surface tension device can be used for formulation in real time for understanding the penetration of drugs in the blood–brain barrier (BBB), understanding the solubility of drugs, development of a screen to test a drugs toxicity, determining the physicochemical properties of oxidized phospholipids, and development of new surfactant/polymers.
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A.3) which, as of early 2016, includes 20 different protein families. Most members of this transporter superfamily catalyze cation uptake and/or efflux, however one subfamily, the flippases, (TC# 3.A.3.8) is involved in flipping phospholipids to maintain the asymmetric nature of the biomembrane. In humans, P-type ATPases serve as a basis for nerve impulses, relaxation of muscles, secretion and absorption in the kidney, absorption of nutrient in the intestine and other physiological processes.
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A lipid emulsion (intralipid) 20% Lipid emulsion or fat emulsion refers to an emulsion of lipid for human intravenous use. It is often referred to by the brand name of the most commonly used version, Intralipid, which is an emulsion of soy bean oil, egg phospholipids and glycerin, and is available in 10%, 20% and 30% concentrations. The 30% concentration is not approved for direct intravenous infusion, but should be mixed with amino acids and dextrose as part of a total nutrient admixture.
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As a mammary gland, the breast comprises lobules (milk glands at each lobe-tip) and the lactiferous ducts (milk passages), which widen to form an ampulla (sac) at the nipple. # Adipose tissue. The fat tissue of the breast is composed of lipidic fluid (60–85% weight) that is 90–99 per cent triglycerides, free fatty acids, diglycerides, cholesterol phospholipids, and minute quantities of cholesterol esters, and monoglycerides; the other components are water (5–30% weight) and protein (2–3% weight). # The skin envelope.
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Fixed nitrogen sources are required for most organisms to synthesize proteins, nucleic acids and other cellular components. Depending on the enzyme capabilities of the organism, nitrogen may be provided as bulk protein, such as soy meal; as pre-digested polypeptides, such as peptone or tryptone; or as ammonia or nitrate salts. Cost is also an important factor in the choice of a nitrogen source. Phosphorus is needed for production of phospholipids in cellular membranes and for the production of nucleic acids.
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Sterol carrier proteins (also known as nonspecific lipid transfer proteins) is a family of proteins that transfer steroids and probably also phospholipids and gangliosides between cellular membranes. These proteins are different from plant nonspecific lipid transfer proteins but structurally similar to small proteins of unknown function from Thermus thermophilus. This domain is involved in binding sterols. The human sterol carrier protein 2 (SCP2) is a basic protein that is believed to participate in the intracellular transport of cholesterol and various other lipids.
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Viral replication is nucleo-cytoplasmic. Replication follows the DNA strand displacement model, and DNA-templated transcription is the method of transcription. The virus exits the host cell by lysis via lytic phospholipids, with passive diffusion being the mechanism behind transmission routes. In three dimensional recreations of PBCV-1 (Paramecium bursaria chlorella virus), a prototype of chlorovirus, it is seen that the spike first contacts the host’s cell wall and is aided by fibres in order to secure the virus to the host.
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LPL will remove triglycerides from VLDL for storage or energy production. VLDL now meets back up with HDL where apoC-II is transferred back to HDL (but keeps apoE). HDL also transfers cholesteryl esters to the VLDL in exchange for phospholipids and triglycerides via cholesterylester transfer protein (CETP). As more and more triglycerides are removed from the VLDL because of the action of LPL and CETP enzymes, the composition of the molecule changes, and it becomes intermediate-density lipoprotein (IDL).
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This is referred to as cooperative binding. We also see cooperativity in large chain molecules made of many identical (or nearly identical) subunits (such as DNA, proteins, and phospholipids), when such molecules undergo phase transitions such as melting, unfolding or unwinding. This is referred to as subunit cooperativity. However, the definition of cooperativity based on apparent increase or decrease in affinity to successive ligand binding steps is problematic, as the concept of "energy" must always be defined relative to a standard state.
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Liposomes are composed of vesicular bilayers, lamellae, made of biocompatible and biodegradable lipids such as sphingomyelin, phosphatidylcholine, and glycerophospholipids. Cholesterol, a type of lipid, is also often incorporated in the lipid-nanoparticle formulation. Cholesterol can increase stability of a liposome and prevent leakage of a bilayer because its hydroxyl group can interact with the polar heads of the bilayer phospholipids. Liposomes have the potential to protect the drug from degradation, target sites for action, and reduce toxicity and adverse effects.
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Instead they possess a DHR2 domain which mediates G protein activation by stabilising it in its nucleotide free state. They also contain a DHR1 domain which, in many DOCK family members, interacts with phospholipids. Dock7 shares the highest level of sequence similarity with Dock6 and Dock8, the other members of the DOCK-C subfamily. However, the specificity of the Dock7 DHR2 domain appears to resemble that of DOCK-A/B subfamily proteins in that it binds Rac but not Cdc42.
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Folate deficiency during gestation or infancy due to development by the fetus or infant of autoantibodies to the folate receptor might result in various developmental disorders. Studies suggest that insufficient folate and vitamin B12 status may contribute to major depressive disorder and that supplementation might be useful in this condition. The role of vitamin B12 and folate in depression is due to their role in transmethylation reactions, which are crucial for the formation of neurotransmitters (e.g. serotonin, epinephrine, nicotinamides, purines, phospholipids).
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Experimental evidence has been collected on the interaction of alpha-synuclein with membrane and its involvement with membrane composition and turnover. Yeast genome screening has found that several genes that deal with lipid metabolism and mitochondrial fusion play a role in alpha-synuclein toxicity. Conversely, alpha-synuclein expression levels can affect the viscosity and the relative amount of fatty acids in the lipid bilayer. Alpha-synuclein is known to directly bind to lipid membranes, associating with the negatively charged surfaces of phospholipids.
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A subset of AHAA appear to mimic the activity of lupus anticoagulant and increase Apo-H binding to phospholipids. These two activities can be differentiated by the binding to Apo-H domains, whereas binding to the 5th domain promotes that anti-coagulant activity binding to the more N-terminal domains promotes lupus anticoagulant-like activities. structure of Apolipoprotein H AAHA interferes with factor Xa inhibition by Apo-H increasing factor Xa generation. However, like Apo-H the Lupus anticoagulant inhibits factor Xa generation.
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Dietary fats are emulsified in the duodenum by soaps in the form of bile salts and phospholipids, such as phosphatidylcholine. The fat droplets thus formed can be attacked by pancreatic lipase. Structure of a bile acid (cholic acid), represented in the standard form, a semi-realistic 3D form, and a diagrammatic 3D form Diagrammatic illustration of mixed micelles formed in the duodenum in the presence of bile acids (e.g. cholic acid) and the digestion products of fats, the fat soluble vitamins and cholesterol.
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Generally speaking, all bacteria contain a fraction (1-2%) of phosphorus in their biomass due to its presence in cellular components, such as membrane phospholipids and DNA. Therefore, as bacteria in a wastewater treatment plant consume nutrients in the wastewater, they grow and phosphorus is incorporated into the bacterial biomass. When PAOs grow they not only consume phosphorus for cellular components but also accumulate large quantities of polyphosphate within their cells. Thus, the phosphorus fraction of phosphorus accumulating biomass is 5-7%.
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The milk fat globule is surrounded by a phospholipid trilayer containing associated proteins, carbohydrates, and lipids derived primarily from the membrane of the secreting mammary epithelial cell (lactocyte). This trilayer is collectively known as MFGM. While MFGM makes up only an estimated 2% to 6% of the total milk fat globule, it is an especially rich phospholipid source, accounting for the majority of total milk phospholipids. In contrast, the inner core of the milk fat globule is composed predominantly of triacylglycerols.
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In molecular biology, copines is a name for the group of human proteins that includes members such as CPNE1, CPNE4, CPNE6, and CPNE8. These are highly conserved, calcium-dependent membrane proteins found in a variety of eukaryotes. The domain structure of these 55 kDa proteins suggests that they may have a role in membrane trafficking in some prokaryotes as well as eukaryotes. Copines contains two C2 domains which play a role in signal transduction by binding to calcium, phospholipids, or polyphosphates.
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Another protocell model is the Jeewanu. First synthesized in 1963 from simple minerals and basic organics while exposed to sunlight, it is still reported to have some metabolic capabilities, the presence of semipermeable membrane, amino acids, phospholipids, carbohydrates and RNA-like molecules. However, the nature and properties of the Jeewanu remains to be clarified. Electrostatic interactions induced by short, positively charged, hydrophobic peptides containing 7 amino acids in length or fewer, can attach RNA to a vesicle membrane, the basic cell membrane.
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This system of replicating > clays and their metabolic phenotype then evolved into the sulfide rich > region of the hotspring acquiring the ability to fix nitrogen. Finally > phosphate was incorporated into the evolving system which allowed the > synthesis of nucleotides and phospholipids. If biosynthesis recapitulates > biopoiesis, then the synthesis of amino acids preceded the synthesis of the > purine and pyrimidine bases. Furthermore, the polymerization of the amino > acid thioesters into polypeptides preceded the directed polymerization of > amino acid esters by polynucleotides.
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Gastrointestinal perforation can be caused by VEGF inhibition although the mechanism is unknown. Abscesses, diverticula as well as bowel resection and anastomosis have been related to some cases. Haemorrhage and thrombosis can occur when VEGF is inhibited as VEGF promotes endothelial cell survival and helps maintaining vascular integrity. When VEGF is inhibited, the regenerative capacity of endothelial cells may diminish and pro-coagulant phospholipids could be exposed on the plasma membrane or the underlying matrix, possibly leading to either thrombosis or haemorrhage.
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Research has been conducted on in vivo biodistribution and highly efficient tumor targeting of carbon nanotubes in mice for cancer therapy. Investigations are being done on the biodistribution of radio- labelled SWNTs in mice by in vivo positron emission tomography (PET), ex vivo biodistribution and Raman spectroscopy. It was found that SWNTs that are functionalized with phospholipids bearing polyethylene glycol (PEG) are surprisingly stable in vivo. The effect of PEG chain length on the biodistribution and circulation of the SWNTs was studied.
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Every living cell is encased in a membrane that separates it from its surroundings. Cellular membranes are composed of a phospholipid matrix and proteins, typically in the form of a bilayer. Phospholipids are derived from glycerol with two of the glycerol hydroxyl (OH) protons replaced by fatty acids as an ester, and the third hydroxyl proton has been replaced with phosphate bonded to another alcohol.Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. .
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The carbon dioxide released by sodium bicarbonate aids in the expansion and the unilateral stretching of the protein network during production. A variety of emulsifiers can be used to stabilize the meat analog system. These could include, but are not limited to polyglycerol monoesters of fatty acids, monoacylglycerol esters of dicarboxylic acids, sucrose monoesters of fatty acids, and phospholipids. Polyglycerol monoesters consist on average of 2 to 10 glycerol units and an average of one acyl fatty acid group per glycerol component.
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Liposomes are composite structures made of phospholipids and may contain small amounts of other molecules. Though liposomes can vary in size from low micrometer range to tens of micrometers, unilamellar liposomes, as pictured here, are typically in the lower size range, with various targeting ligands attached to their surface, allowing for their surface-attachment and accumulation in pathological areas for treatment of disease.Torchilin, VP “Multifunctional Nanocarriers.” Adv Drug Deliv Rev 2006 Dec; 58 (14): 1532-55 doi: 10.1016/j.addr.2006.09.
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It is much more important to the metabolism of plants, particularly many grasses, and silicic acid (a type of silica) forms the basis of the striking array of protective shells of the microscopic diatoms. Phosphorus is essential for life. As phosphate, it is a component of DNA, RNA, ATP, and also the phospholipids that form all cell membranes. Demonstrating the link between phosphorus and life, elemental phosphorus was historically first isolated from human urine, and bone ash was an important early phosphate source.
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Within the envelope membranes, in the region called the stroma, there is a system of interconnecting flattened membrane compartments, called the thylakoids. The thylakoid membrane is quite similar in lipid composition to the inner envelope membrane, containing 78% galactolipids, 15.5% phospholipids and 6.5% sulfolipids in spinach chloroplasts. The thylakoid membrane encloses a single, continuous aqueous compartment called the thylakoid lumen. These are the sites of light absorption and ATP synthesis, and contain many proteins, including those involved in the electron transport chain.
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Nucleic acids, phospholipids, and amino acids are important cell building- blocks, which are greatly needed by highly proliferating cells, such as tumor cells. Due to the key position of pyruvate kinase within glycolysis, the tetramer:dimer ratio of PKM2 determines whether glucose carbons are converted to pyruvate and lactate under the production of energy (tetrameric form) or channelled into synthetic processes (dimeric form). In tumor cells, PKM2 is mainly in the dimeric form and has, therefore, been termed Tumor M2-PK.
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An annotated diagram of the alveolus Type II cells are cuboidal and much smaller than type I cells. They are the most numerous cells in the alveoli, yet do not cover as much surface area as the squamous type I cells. Type II cells in the alveolar wall contain secretory organelles known as lamellar bodies that fuse with the cell membranes and secrete pulmonary surfactant. This surfactant is a film of fatty substances, a group of phospholipids that reduce alveolar surface tension.
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Egg lecithin is usually extracted chemically using ethanol, acetone, petroleum ether but not benzene or hexane due to restrictions on residual solvents by the pharmaceutical regulations.ICH Topic Q3C (R4) Impurities: Guideline for Residual Solvents It is an emulsifier, especially for parenteral use since it does not need to be metabolized. In aqueous solution, its phospholipids can form either liposomes, bilayer sheets, micelles, or lamellar structures, depending on hydration and temperature. This results in a type of surfactant that is usually classified as amphipathic.
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As a mammary gland, the breast comprises lobules (milk glands at each lobe-tip) and the lactiferous ducts (milk passages), which widen to form an ampulla (sac) at the nipple. # Adipose tissue. The fat tissue of the breast is composed of lipidic fluid (60–85% weight) that is 90–99 per cent triglycerides, free fatty acids, diglycerides, cholesterol phospholipids, and minute quantities of cholesterol esters, and monoglycerides; the other components are water (5–30% weight) and protein (2–3% weight). # Fatty tissue.
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Humans can convert short-chain omega−3 fatty acids to long-chain forms (EPA, DHA) with an efficiency below 5%. The omega−3 conversion efficiency is greater in women than in men, but less studied. Higher ALA and DHA values found in plasma phospholipids of women may be due to the higher activity of desaturases, especially that of delta-6-desaturase. These conversions occur competitively with omega−6 fatty acids, which are essential closely related chemical analogues that are derived from linoleic acid.
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For topical applications on skin, specialized lipids like phospholipids and sphingolipids may be used to make drug-free liposomes as moisturizers, and with drugs such as for anti-ultraviolet radiation applications. In biomedical research, unilamellar liposomes are extremely useful to study biological systems and mimicking cell functions. As a living cell is very complicated to study, unilamellar liposomes provide a simple tool to study membrane interaction events such as membrane fusion, protein localization in the plasma membrane, study ion channels, etc.
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Chylomicron structure ApoA, ApoB, ApoC, ApoE (apolipoproteins); T (triacylglycerol); C (cholesterol); green (phospholipids) Chylomicrons transport lipids absorbed from the intestine to adipose, cardiac, and skeletal muscle tissue, where their triglyceride components are hydrolyzed by the activity of the lipoprotein lipase, allowing the released free fatty acids to be absorbed by the tissues. When a large portion of the triglyceride core has been hydrolyzed, chylomicron remnants are formed and are taken up by the liver, thereby also transferring dietary fat to the liver.
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The cause of asteroid hyalosis is unknown, but it has been associated with diabetes mellitus, hypertension, hypercholesterolemia, and, in certain animals, tumors of the ciliary body. In dogs, asteroid hyalosis is considered to be an age related change. The asteroid bodies are made up of hydroxylapatite, which in turn consists of calcium and phosphates or phospholipids. While asteroid hyalosis does not usually severely affect vision, the floating opacities can be quite annoying, and may interfere significantly with visualization and testing of the retina.
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Structure of a chylomicron. ApoA, ApoB, ApoC, ApoE are apolipoproteins; green particles are phospholipids; T is triacylglycerol; C is cholesterol ester. A lipoprotein is a biochemical assembly whose primary purpose is to transport hydrophobic lipid (also known as fat) molecules in water, as in blood plasma or other extracellular fluids. They consist of a Triglyceride and Cholesterol center, surrounded by a phospholipid outer shell, with the hydrophilic portions oriented outward toward the surrounding water and lipophilic portions oriented inward toward the lipid center.
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Where phosphatidylcholine is the principal phospholipid in animals, phosphatidylethanolamine is the principal one in bacteria. One of the primary roles for phosphatidylethanolamine in bacterial membranes is to spread out the negative charge caused by anionic membrane phospholipids. In the bacterium E. coli, phosphatidylethanolamine play a role in supporting lactose permeases active transport of lactose into the cell, and may play a role in other transport systems as well. Phosphatidylethanolamine plays a role in the assembly of lactose permease and other membrane proteins.
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They used Sendai virus to force human and mouse cells to fuse and form a heterokaryon. Using antibody staining, they were able to show that the mouse and human proteins remained segregated to separate halves of the heterokaryon a short time after cell fusion. However, the proteins eventually diffused and over time the border between the two halves was lost. Lowering the temperature slowed the rate of this diffusion by causing the membrane phospholipids to transition from a fluid to a gel phase.
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In molecular biology, the fatty acid metabolism regulator protein FadR, is a bacterial transcription factor. Bacteria regulate membrane fluidity by manipulating the relative levels of saturated and unsaturated fatty acids within the phospholipids of their membrane bilayers. In Escherichia coli, the transcription factor, FadR, functions as a switch that co-ordinately regulates the machinery required for fatty acid beta-oxidation and the expression of a key enzyme in fatty acid biosynthesis. This single [repressor controls the transcription of the whole fad regulon.
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Since SP-B has a major role in surfactant biogenesis and spreading of surfactant and lipid layer, any disruption to existence of SP-B results in ineffective respiration and lethal pulmonary conditions at birth. Pathology manifestation in full-term infant resembles characteristics of newborn with Respiratory Distress Syndrome. Imaging of epithelial type II cells with SP-B deficiency shows immature lamellar bodies without tightly packed membranes, but rather with loose and unorganized membranes. The ratio of phospholipid-protein also decreases with abnormal phospholipids.
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In the human endocrine system, a spongiocyte is a cell in the zona fasciculata of the adrenal cortex containing lipid droplets that show pronounced vacuolization, due to the way the cells are prepared for microscopic examination. The lipid droplets contain neutral fats, fatty acids, cholesterol, and phospholipids; all of which are precursors to the steroid hormones secreted by the adrenal glands. The principal hormone secreted from the cells of the zona fasciculata are glucocorticoids, but some androgens are produced as well.
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The best characterized function of Protein S is its role in the anti coagulation pathway, where it functions as a cofactor to Protein C in the inactivation of Factors Va and VIIIa. Only the free form has cofactor activity. Protein S binds to negatively charged phospholipids via the carboxylated Gla domain. This property allows Protein S to facilitate the removal of cells that are undergoing apoptosis, a form of structured cell death used by the body to remove unwanted or damaged cells.
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Shewanella violacea has an abnormally high percent of polyunsaturated fatty acids (PUFA) integrated into its phospholipids. In Shewanella violacea 14% of its fatty acids are eicosapentaenoic acids (EPA) which are a specific type of polyunsaturated fatty acid also known as 20:5ω3. Increased PUFA concentrations decrease the membrane fluidity and help the bacterium thrive in the cold temperatures. The exact function of the unusual lipid composition found in S. violacea and other members of Group 1 Shewanella species is not yet fully understood.
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Specific organismal chemical signatures can be used to detect biomass of more cryptic organisms, such as AM fungi or soil bacteria. Lipids, more specifically phospholipids and neutral lipids, contain fatty acids connected to a glycerol backbone. The fatty acid composition of organisms varies, and the proportions of specific fatty acids can be organism specific. For example, in AM fungi the proportion of the fatty acids, 16:1ω5 and 18:1ω7, in the phospholipid portion account for approximately 58% of total fatty acid composition.
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Magnetotactic bacteria is a class of bacteria known to use magnetic fields for orientation. These bacteria demonstrate a behavioral phenomenon known as magnetotaxis which is how the bacterium orients itself and migrates in the direction along the Earth's magnetic field lines. The bacteria contain magnetosomes, which are nanometer- sized particles of magnetite or iron sulfide enclosed within the bacterial cells. The magnetosomes are surrounded by a membrane composed of phospholipids and fatty acids and contain at least 20 different proteins.
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Lipoproteins have long been divided into 5 subgroups, by density/size (an inverse relationship), which also correlates with function and incidence of cardiovascular events. Unlike the larger lipoprotein particles which deliver fat molecules to cells, HDL particles remove fat molecules from cells which need to export fat molecules. The lipids carried include cholesterol, phospholipids, and triglycerides; amounts of each are quite variable. Increasing concentrations of HDL particles are strongly associated with decreasing accumulation of atherosclerosis within the walls of arteries.
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The annexins are a family of calcium-dependent phospholipid- binding proteins. Members of the annexin family contain 4 internal repeat domains, each of which includes a type II calcium-binding site. The calcium- binding sites are required for annexins to aggregate and cooperatively bind anionic phospholipids and extracellular matrix proteins. This gene encodes a divergent member of the annexin protein family in which all four homologous type II calcium-binding sites in the conserved tetrad core contain amino acid substitutions that ablate their function.
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From 1940 to 1945, McManus served in the Royal Canadian Army Medical Corps. While he was stationed in England at Aldershot outside of Farnsborough at No.8 Canadian General Hospital, he met Professor J. R. Baker. It was in Baker's laboratory in the Department of Zoology and Comparative Anatomy at Oxford University, Dr. McManus developed a number of histochemical procedures including a Sudan black B procedure for demonstrating phospholipids. This work was to mark the beginning of his influence in identifying the chemistry of microscopic structure.
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Attempted suicide by intake of a large dose of quinine has caused irreversible tunnel vision and very severe visual impairment. Patients treated with quinine may also suffer from low blood sugar, especially if it is administered intravenously, and hypotension (low blood pressure). Quinine, like chloroquine, inactivates enzymes in the lysosomes of cells and has an anti-inflammatory effect, hence its use in the treatment of rheumatoid arthritis. However, inactivation of these enzymes can also cause abnormal accumulation of glycogen and phospholipids in lysosomes, causing toxic myopathy.
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Cytosolic phospholipase A2 associates with natural membranes in response to physiological increases in Ca2+ and selectively hydrolyses arachidonyl phospholipids, the aligned region corresponds the carboxy-terminal Ca2+-independent catalytic domain of the protein as discussed in. The systematic name of this enzyme class is 2-lysophosphatidylcholine acylhydrolase. Other names in common use include lecithinase B, lysolecithinase, phospholipase B, lysophosphatidase, lecitholipase, phosphatidase B, lysophosphatidylcholine hydrolase, lysophospholipase A1, lysophopholipase L2, lysophospholipase transacylase, neuropathy target esterase, NTE, NTE-LysoPLA, and NTE-lysophospholipase. This enzyme participates in glycerophospholipid metabolism.
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Plasma Gelsolin is a sticky protein known to bind to a number of peptides and proteins: Actin (see also: Relationships with actin), Apo-H, Aβ, α-Synuclein, Integrin, Tcp-1, Fibronectin, Syntaxin-4, Tropomyosin, fatty acids and phospholipids (see also: Binding and inactivation of diverse inflammatory mediators): LPA, LPS (endotoxin), LTA, PAF, S1P, polyphosphoinositides including PIP2; and nucleic acids: Ap3A, ATP, ADP. PIP2, a phospholipid component of cell membranes, competes with ATP and actin for pGSN binding, and will dissociate F-Actin-capped pGSN.
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Bavituximab is an antibody that binds to complexes of the phosphatidylserine-binding plasma protein β2-glycoprotein 1 and anionic phospholipids. In laboratory experiments, treatment with bavituximab was found to rescue mice from otherwise lethal infections of mouse cytomegalovirus (CMV), and Pichinde virus, a model of Lassa fever virus. Proposed mechanisms for this therapeutic effect included bavituximab directly clearing infectious virus from the bloodstream, and the induction of antibody-dependent cellular cytotoxicity of virus-infected cells. Bavituximab inhibited replication of influenza in preliminary experiments in chicken eggs.
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The middle structure is a triglyceride composed of oleoyl, stearoyl, and palmitoyl chains attached to a glycerol backbone. At the bottom is the common phospholipid phosphatidylcholine. In biology and biochemistry, a lipid is a macrobiomolecule that is soluble in nonpolar solvents. Non-polar solvents are typically hydrocarbons used to dissolve other naturally occurring hydrocarbon lipid molecules that do not (or do not easily) dissolve in water, including fatty acids, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E, and K), monoglycerides, diglycerides, triglycerides, and phospholipids.
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Marzipan is a food emulsion that contains four phases: a solid phase of suspended particles including almonds and sugars, a suspended air pocket phase formed from incorporated air during mixing, a water phase, and a lipid phase from almond oil. The phases can separate when left alone for long periods of time. It is stabilized by the phospholipids and triglycerides found in the almond cells. The fatty acids found in almonds include saturated fats such as stearic acid and unsaturated fats such as linoleic acid.
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These are unique secretory organelles that store phospholipids and cholesterol and are used for rapid mitotic events needed for dispersal of infectious cells (Coppens 2005). The gametocyst of Nematopsis, the cyst in which gametes are produced in gregarines, is spherical and around 110-160 μm in diameter (Prasadan and Janardana 2001). They are generally found in close contact with host tissue (gastro-intestinal tract, gills or mantle) (Prasadan and Janardana 2001). The surface of the gametocyst is wrinkled and has a central pore at one pole.
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Human talin-1 is 270.0 kDa molecular weight and 2541 amino acids. The N-terminal region of talin-1 is ~50 kDa in size and homologous to members of the ERM protein family which have a globular FERM domain (residues 86-400) that links the actin cytoskeleton to adhesion proteins. In addition to F-actin, the N-terminal region of talin-1 binds layilin, β1- and β3-integrin, and focal adhesion kinase. Talin-1 N-terminal region also binds acidic phospholipids for insertion into lipid bilayers.
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Posaconazole works by disrupting the close packing of acyl chains of phospholipids, impairing the functions of certain membrane-bound enzyme systems such as ATPase and enzymes of the electron transport system, thus inhibiting growth of the fungi. It does this by blocking the synthesis of ergosterol by inhibiting of the enzyme lanosterol 14α-demethylase and accumulation of methylated sterol precursors. Posaconazole is significantly more potent at inhibiting 14-alpha demethylase than itraconazole.Brunton L, Lazo J, Parker K. Goodman and Gilman's The Pharmacological Basis of Therapeutics.
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However, antiphospholipid antibodies bind phospholipids at sites similar to sites bound by anti-coagulants such as PAP1 sites and augment anti-coagulation activity. This contrasts with the major, specific, activity of AAHA, defining a subset of anti-cardiolipin antibodies that specifically interacts with Apo-H. AHAA only inhibits the anti-coagulation activity in the presence of Apo-H and the AAHA component of ACLA correlates with a history of frequent thrombosis. This can be contrasted with lupus anticoagulant which inhibits agglutination in the presence of thrombin.
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The occurrence of seminal vesicles, in spite of their interspecific variability in size, gross morphology and function, has not been related to the mode of fertilization. They are typically paired, multi- chambered, and connected with the sperm duct, and have been reported to play a glandular and a storage function. Seminal vesicle secretion may include steroids and steroid glucuronides, with hormonal and pheromonal functions, but it appears to be primarily constituted of mucoproteins, acid mucopolysaccharides, and phospholipids. Fish ovaries may be of two types: gymnovarian or cystovarian.
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In order to conduct DNA separation by silica adsorption, a sample (this may be anything from purified cells to a tissue specimen) is placed onto a specialized chip and lysed. The resultant mix of proteins, DNA, phospholipids, etc., is then run through the channel where the DNA is adsorbed by a silica surface in the presence of solutions with high ionic strength. The highest DNA adsorption efficiencies occur in the presence of buffer solution with a pH at or below the pKa of the surface silanol groups.
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For this, the solution of the solubilized protein is subject to dialysis or ion exchange chromatography in the presence of phospholipids or membrane lipid mixtures to remove the surfactant. For example, 95% of the OTG can be removed from a 43 mM surfactant solution under standard conditions within 6 hours. Octylthioglucoside (15 mM) is clearly superior to its O-analog octyl glucoside (OT) in the solubilization and stabilization against thermal and light-induced denaturation of the light- driven proton pump Bacteriorhodopsin from the biomembranes of halobacteria.
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Liposomes are composite structures made of phospholipids and may contain small amounts of other molecules. Though liposomes can vary in size from low micrometer range to tens of micrometers, unilamellar liposomes, as pictured here, are typically in the lower size range with various targeting ligands attached to their surface allowing for their surface-attachment and accumulation in pathological areas for treatment of disease. Drug-loaded polymeric micelle formed from self-assembly of amphiphilic block copolymers in aqueous media. Drug-loaded polymeric micelles with various targeting functions.
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DNA contains the chemical blueprint for the synthesis of proteins which are made up of amino acid subunits. Cell membranes contain fatty acid esters such as phospholipids. An α-amino acid has a central carbon (the α or alpha carbon) which is covalently bonded to a carboxyl group (thus they are carboxylic acids), an amino group, a hydrogen atom and a variable group. The variable group, also called the R group or side chain, determines the identity and many of the properties of a specific amino acid.
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Strictly speaking, phospholipase D is a transphosphatidylase: it mediates the exchange of polar headgroups covalently attached to membrane-bound lipids. Utilizing water as a nucleophile, this enzyme catalyzes the cleavage of the phosphodiester bond in structural phospholipids such as phosphatidylcholine and phosphatidylethanolamine. The products of this hydrolysis are the membrane-bound lipid phosphatidic acid (PA), and choline, which diffuses into the cytosol. As choline has little second messenger activity, PLD activity is mostly transduced by the production of PA. PA is heavily involved in intracellular signal transduction.
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The composition of a membrane can also affect its fluidity. The membrane phospholipids incorporate fatty acids of varying length and saturation. Lipids with shorter chains are less stiff and less viscous because they are more susceptible to changes in kinetic energy due to their smaller molecular size and they have less surface area to undergo stabilizing London forces with neighboring hydrophobic chains. Lipid chains with carbon-carbon double bonds (unsaturated) are more rigid than lipids that are saturated with hydrogens, as double bonds cannot freely turn.
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Diagram of the arrangement of amphipathic lipid molecules to form a lipid bilayer. The yellow polar head groups separate the grey hydrophobic tails from the aqueous cytosolic and extracellular environments. Lipid bilayers form through the process of molecular self-assembly. The cell membrane consists primarily of a thin layer of amphipathic phospholipids that spontaneously arrange so that the hydrophobic "tail" regions are isolated from the surrounding water while the hydrophilic "head" regions interact with the intracellular (cytosolic) and extracellular faces of the resulting bilayer.
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The primary function of alpha-actinin 2 is to crosslink filamentous actin molecules and titin molecules from adjoining sarcomeres at Z-discs, a function that is modulated by phospholipids. It is clear from studies by Hampton et al. that this crosslinking can assume a variety of conformations, with preferences for 60° and 120° angles. Alpha- actinin 2 also functions in docking signalling molecules at Z-discs, and additional studies have also implicated alpha-actinin 2 in the binding of cardiac ion channels, Kv1.5 in particular.
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The enzymatic activity of scramblase depends on the calcium concentration present inside the cell. The calcium concentration inside cells is, under normal conditions, very low; therefore, scramblase has a low activity under resting conditions. Phospholipid redistribution is triggered by increased cytosolic calcium and seems to be scramblase-dependent, resulting in a symmetric distribution of negatively charged phospholipids between both leaflets of the lipid bilayer. All scramblases contain an EF hand-like Ca2+binding domain that is probably responsible for the calcium activation of the enzyme.
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Hydration strongly affects the molecular and electronic structure of membrane phospholipids. 136, 114709 (2012) The lipid bilayer is very thin compared to its lateral dimensions. If a typical mammalian cell (diameter ~10 micrometers) were magnified to the size of a watermelon (~1 ft/30 cm), the lipid bilayer making up the plasma membrane would be about as thick as a piece of office paper. Despite being only a few nanometers thick, the bilayer is composed of several distinct chemical regions across its cross-section.
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The length of glycerophospholipid acyl chain and the degree of saturation are important determinants of many membrane characteristics including the formation of lateral domains that are rich in polyunsaturated fatty acids. Receptor-mediated degradation of glycerophospholipids by phospholipases A(l), A(2), C, and D results in generation of second messengers, such as prostaglandins, eicosanoids, platelet activating factor and diacylglycerol. Thus, neural membrane phospholipids are a reservoir for second messengers. They are also involved in apoptosis, modulation of activities of transporters, and membrane-bound enzymes.
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The mechanism by which Amcinonide causes anti-inflammatory responses is unclear with current research focused on similar topical steroids that may possess the same mechanism.DrugBank.ca: Amcinonide This is thought to occur via the induction of lipocortin (phospholipase A2 inhibitor proteins). Ongoing research predicts that Amcinonide presents the release of arachidonic acid which, in turn, stops the synthesis of the inflammation mediators prostaglandins and leukotrienes. Phospholipase A2 normally causes membrane phospholipids to release arachidonic acid, therefore causing a cascade of reactions leading to inflammation of the skin.
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400px The third mechanism responsible for the translocation is based on the formation of the inverted micelles. Inverted micelles are aggregates of colloidal surfactants in which the polar groups are concentrated in the interior and the lipophilic groups extend outward into the solvent. According to this model, a penetratin dimer combines with the negatively charged phospholipids, thus generating the formation of an inverted micelle inside of the lipid bilayer. The structure of the inverted micelles permits the peptide to remain in a hydrophilic environment.
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The long association with aphids and the limitation of crossover events due to strictly vertical transmission has seen the deletion of genes required for anaerobic respiration, the synthesis of amino sugars, fatty acids, phospholipids, and complex carbohydrates. This has resulted not only in one of the smallest known genomes of any living organism, but also one of the most genetically stable. The symbiotic relationship with aphids began between 160 million and 280 million years ago, and has persisted through maternal transmission and cospeciation. Aphids have developed bacteriocyte cells to house Buchnera.
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A number of PRRs do not remain associated with the cell that produces them. Complement receptors, collectins, ficolins, pentraxins such as serum amyloid and C-reactive protein, lipid transferases, peptidoglycan recognition proteins (PGRs) and the LRR, XA21D are all secreted proteins. One very important collectin is mannan- binding lectin (MBL), a major PRR of the innate immune system that binds to a wide range of bacteria, viruses, fungi and protozoa. MBL predominantly recognizes certain sugar groups on the surface of microorganisms but also binds phospholipids, nucleic acids and non-glycosylated proteins.
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Dock8 shares the same core domain arrangement as all other DOCK proteins, with a DHR2 domain which, in other proteins, contains GEF activity and a DHR1 domain known, in other proteins, to interact with phospholipids. In the YTH system Dock8 was reported to interact with both Rac1 and Cdc42. However, no stable interaction between Dock8 and these small G proteins was observed in a GST-pulldown assay. This may be due to the fact many DOCK-G protein interactions require the presence of adaptor proteins to stabilise the complex and thus facilitate nucleotide exchange.
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The chemical analysis of fatty acids in lipids typically begins with an interesterification step that breaks down their original esters (triglycerides, waxes, phospholipids etc) and converts them to methyl esters, which are then separated by gas chromatography. or analyzed by gas chromatography and mid-infrared spectroscopy. Separation of unsaturated isomers is possible by silver ion (argentation) thin-layer chromatography. Other separation techniques include high-performance liquid chromatography (with short columns packed with silica gel with bonded phenylsulfonic acid groups whose hydrogen atoms have been exchanged for silver ions).
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DPPC is the main phospholipid of pulmonary surfactant, and it is surface-active due to its amphipathic behaviour and its adsorption capacity. However, adsorption is not optimal at human body temperature for DPPC alone, because at 37 °C it is found in a gel phase. The presence of some unsaturated phospholipids (such as dioleoylphosphatidylcholine [DOPC] or phosphatidylglycerol) and cholesterol increases the surfactant's fluidity, so it can adsorb oxygen more efficiently. When this mixture contacts water, for example, it accumulates at the water-air interface and forms a thin superficial pellicule of surfactant.
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The criteria that a protein has to meet to be classified as an annexin are: it has to be capable of binding negatively charged phospholipids in a calcium dependent manner and must contain a 70 amino acid repeat sequence called an annexin repeat. Several proteins consist of annexin with other domains like gelsolin. The basic structure of an annexin is composed of two major domains. The first is located at the COOH terminal and is called the “core” region. The second is located at the NH2 terminal and is called the “head” region.
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Approximately 98% of alveolar wall surface area is due to the presence of type I cells, with type II cells producing pulmonary surfactant covering around 2% of the alveolar walls. Once surfactant is secreted by the type II cells, it must be spread over the remaining type I cellular surface area. Phosphatidylglycerol is thought to be important in spreading of surfactant over the Type I cellular surface area. The major surfactant deficiency in premature infants relates to the lack of phosphatidylglycerol, even though it comprises less than 5% of pulmonary surfactant phospholipids.
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In enzymology, a lysophospholipase () is an enzyme that catalyzes the chemical reaction :2-lysophosphatidylcholine + H2O \rightleftharpoons glycerophosphocholine + a carboxylate Thus, the two substrates of this enzyme are 2-lysophosphatidylcholine and H2O, whereas its two products are glycerophosphocholine and carboxylate. This enzyme belongs to the family of hydrolases, specifically those acting on carboxylic ester bonds. This family consists of lysophospholipase / phospholipase B and cytosolic phospholipase A2 which also has a C2 domain . Phospholipase B enzymes catalyse the release of fatty acids from lysophospholipids and are capable in vitro of hydrolyzing all phospholipids extractable from yeast cells.
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The comparison of cellular fatty acid profiles revealed that the concentrations of iso-C15 : 0 and iso-C17 : 0 3-OH in S. olei were much lower than those in S. alkalisoli, while the concentration of summed feature 3 in S. olei was much higher than that in S. alkalisoli. In the polar lipid profiles, sphingophospholipid and two unknown phospholipids (PL1, PL2) were present in S. alkalisoli but not detected in S. olei; however, PGLs and Ls were present in S. olei but not detected in S. alkalisoli.
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Phosphatidylserine (PS) is the major acidic phospholipid class that accounts for 13–15 % of the phospholipids in the human cerebral cortex [1]. In the plasma membrane, PS is localized exclusively in the cytoplasmic leaflet where it forms part of protein docking sites necessary for the activation of several key signaling pathways. These include the Akt, protein kinase C (PKC) and Raf-1 signaling that is known to stimulate neuronal survival, neurite growth, and synaptogenesis [2–7]. Modulation of the PS level in the plasma membrane of neurons has a significant impact on these signaling processes.
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The scavenger receptor superfamily is defined by its ability to recognize and bind a broad range of common ligands. These ligands include: polyanionic ligands including lipoproteins, apoptotic cells, cholesterol ester, phospholipids, proteoglycans, ferritin, and carbohydrates. This broad recognition range allows scavenger receptors to play an important role in homeostasis and the combating of diseases. This is accomplished via the recognition of various PAMP's and DAMP's, which leads to the removal or scavenging of pathogens with the recognition of PAMP's and the removal of apoptotic cells, self reactive antigens and the products of oxidative stress.
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These polarity complexes are localized at the cytoplasmic side of the cell membrane, asymmetrically within cells. For example, in epithelial cells the PAR and Crumbs complexes are localized along the apical membrane and the Scribble complex along the lateral membrane. Together with a group of signaling molecules called Rho GTPases, these polarity complexes can regulate vesicle transport and also control the localization of cytoplasmic proteins primarily by regulating the phosphorylation of phospholipids called phosphoinositides. Phosphoinositides serve as docking sites for proteins at the cell membrane, and their state of phosphorylation determines which proteins can bind.
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1988 The parameters that are measured are referred to as the glass transition value (Tg) and melting temperature (Tm). These values are measured over time and are comparable between an inert reference sample and the analyte. Changes in the (Tm) and (Tg) values evaluate phase changes (solid, liquid-gel, liquid, etc.) in which an endothermic or exothermic process occurs. This technique is useful for monitoring the phase changes in phospholipids by providing information such as the amount of heat released or absorbed and time for phase transitions to occur, etc.
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General chemical structures of phosphotidylethanol, where R1 and R2 are fatty acid chains Phosphatidylethanols (PEth) are a group of phospholipids formed only in the presence of ethanol via the action of phospholipase D (PLD). The lipid accumulates in the brain and competes at agonists sites of lipid-gated ion channels contributing to alcohol intoxication. The chemical similarity of PEth to phosphatidic acid (PA) and phosphatidylinositol 4,5-bisphosphate (PIP2) suggest a likely broad perturbation to lipid signaling, the exact role of PEth as a competitive lipid ligand has not been studied extensively.
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Cholesterol interacts preferentially, although not exclusively, with sphingolipids due to their structure and the saturation of the hydrocarbon chains. Although not all of the phospholipids within the raft are fully saturated, the hydrophobic chains of the lipids contained in the rafts are more saturated and tightly packed than the surrounding bilayer. Cholesterol is the dynamic "glue" that holds the raft together. Due to the rigid nature of the sterol group, cholesterol partitions preferentially into the lipid rafts where acyl chains of the lipids tend to be more rigid and in a less fluid state.
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Ceramide-based lipids self- aggregate in cell membranes and form separate phases less fluid than the bulk phospholipids. These sphingolipid-based microdomains, or "lipid rafts" were originally proposed to sort membrane proteins along the cellular pathways of membrane transport. At present, most research focuses on the organizing function during signal transduction. Sphingolipids are synthesized in a pathway that begins in the ER and is completed in the Golgi apparatus, but these lipids are enriched in the plasma membrane and in endosomes, where they perform many of their functions.
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The primary biological importance of phosphates is as a component of nucleotides, which serve as energy storage within cells (ATP) or when linked together, form the nucleic acids DNA and RNA. The double helix of our DNA is only possible because of the phosphate ester bridge that binds the helix. Besides making biomolecules, phosphorus is also found in bone and the enamel of mammalian teeth, whose strength is derived from calcium phosphate in the form of hydroxyapatite. It is also found in the exoskeleton of insects, and phospholipids (found in all biological membranes).
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The function of this hydrophobic tunnel is unknown, though two hypotheses have been postulated concerning its utility. The first is that the binding of the terminal phospholipids alters the conformation of the active sites, implying that the tunnel acts as an effector, only allowing the enzyme to be active in certain areas of the cell. The second hypothesis postulates that the tunnel regulates lipid membrane rigidity through its degradation of phenolic hydrocarbons and ability to bind to other lipids. Studies have shown that phenolic hydrocarbons affect the functional and structural properties of cell membranes.
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To address this problem, Wächtershäuser proposed that concentration might occur by concentration upon ("adsorption to") the surfaces of minerals. With the accumulation of enough amphipathic molecules (such as phospholipids), a bilayer will self-organize, and any molecules caught inside will become the contents of a liposome, and would be concentrated enough to allow chemical reactions to transform organic molecules into prebiotic molecules. Although developed for his own iron-sulfur world model, the idea of the primordial sandwich has also been adopted by some adherents of the RNA world model.
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In plants, ATP citrate lyase generates acetyl-CoA for cytosolically-synthesized metabolites; Acetyl-CoA is not transported across subcellular membranes of plants. Such metabolites include: elongated fatty acids (used in seed oils, membrane phospholipids, the ceramide moieties of sphingolipids, cuticle, cutin, and suberin); flavonoids; malonic acid; acetylated phenolics, alkaloids, isoprenoids, anthocyanins, and sugars; and, mevalonate-derived isoprenoids (e.g., sesquiterpenes, sterols, brassinosteroids); malonyl and acyl-derivatives (d-amino acids, malonylated flavonoids, acylated, prenylated and malonated proteins). De novo fatty acid biosynthesis in plants occurs in plastids; thus, ATP citrate lyase is not relevant to this pathway.
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AE1 in human red blood cells has been shown to transport a variety of inorganic and organic anions. Divalent anions may be symported with H+. Additionally, it catalyzes flipping of several anionic amphipathic molecules such as sodium dodecyl sulfate (SDS) and phosphatidic acid from one monolayer of the phospholipid bilayer to the other monolayer. The rate of flipping is sufficiently rapid to suggest that this AE1-catalyzed process is physiologically important in red blood cells and possibly in other animal tissues as well. Anionic phospholipids and fatty acids are likely to be natural substrates.
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A549 cells, as found in the lung tissue of their origin, are squamous and responsible for the diffusion of some substances, such as water and electrolytes, across alveoli. If A549 cells are cultured in vitro, they grow as a monolayer; adherent or attaching to the culture flask. The cells are able to synthesize lecithin and contain high levels of unsaturated fatty acids, which are important to maintain membrane phospholipids. A549 cells are widely used as a type II pulmonary epithelial cell model for drug metabolism and as a transfection host.
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The three main structures phospholipids form spontaneously in solution: the liposome (a closed bilayer), the micelle and the bilayer. A protocell is a self-organized, self-ordered, spherical collection of lipids proposed as a stepping-stone to the origin of life. A central question in evolution is how simple protocells first arose and differed in reproductive contribution to the following generation driving the evolution of life. Although a functional protocell has not yet been achieved in a laboratory setting, there are scientists who think the goal is well within reach.
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Choline is an important methyl donor involved in one-carbon metabolism that also becomes incorporated into phospholipids and the neurotransmitter acetylcholine. Because of its role in cellular synthesis, choline is an important nutrient during the prenatal and early postnatal development of offspring as it contributes heavily to the development of the brain. A study found that rats that were given supplements of choline in utero or in the weeks following birth had superior memories. The changes appeared to be a result of physical changes to the hippocampus, the area of the brain responsible for memory.
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Quisqualic acid The mGluRs in group I, including mGluR1 and mGluR5, are stimulated most strongly by the excitatory amino acid analog L-quisqualic acid. Stimulating the receptors causes the associated enzyme phospholipase C to hydrolyze phosphoinositide phospholipids in the cell's plasma membrane. This leads to the formation of inositol 1,4,5-trisphosphate (IP3) and diacyl glycerol. Due to its hydrophilic character, IP3 can travel to the endoplasmic reticulum, where it induces, via fixation on its receptor, the opening of calcium channels increasing in this way the cytosolic calcium concentrations.
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The bacterial cell is surrounded by a cell membrane, which is made primarily of phospholipids. This membrane encloses the contents of the cell and acts as a barrier to hold nutrients, proteins and other essential components of the cytoplasm within the cell. Unlike eukaryotic cells, bacteria usually lack large membrane-bound structures in their cytoplasm such as a nucleus, mitochondria, chloroplasts and the other organelles present in eukaryotic cells. However, some bacteria have protein-bound organelles in the cytoplasm which compartmentalize aspects of bacterial metabolism, such as the carboxysome.
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Hydrolysis of phosphatidylcholine (PC) by ARF-activated PLD produces phosphatidic acid (PA). PA subsequently recruits molecules that shape the inner face of the lipid bilayer, facilitating vesicle formation. Local enrichment of acidic phospholipids help recruit adaptor proteins (AP) and coat proteins (CP) to the membrane, initiating the budding of the vesicle. Vesicle fission is ultimately mediated by dynamin, which itself is a downstream effector of PA. Mammalian PLD directly interacts with kinases like PKC, ERK, TYK and controls the signalling indicating that PLD is activated by these kinases.
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Eukaryotic cell membrane Comparison of Eukaryotes vs. Prokaryotes The cell membrane (also known as the plasma membrane, or cytoplasmic membrane, and historically referred to as the plasmalemma) is the semipermeable membrane of a cell that surrounds and encloses its contents of cytoplasm and nucleoplasm. The cell membrane separates the cell from the surrounding interstitial fluid, the main component of the extracellular fluid.Kimball's Biology pages , Cell Membranes The cell membrane consists of a lipid bilayer, including cholesterols (a lipid component) that sit between phospholipids to maintain their fluidity at various temperatures.
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This core also carries varying numbers of triglycerides and other fats and is surrounded by a shell of phospholipids and unesterified cholesterol, as well as the single copy of Apo B-100. LDL particles are approximately 22 nm (0.00000087 in.) to 27.5 nm in diameter and have a mass of about 3 million daltons. Since LDL particles contain a variable and changing number of fatty acid molecules, there is a distribution of LDL particle mass and size. Determining the structure of LDL has been a tough task because of its heterogeneous structure.
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Enzymes of the smooth ER are vital to the synthesis of lipids, including oils, phospholipids, and steroids. Sex hormones of vertebrates and the steroid hormones secreted by the adrenal glands are among the steroids produced by the smooth ER in animal cells. The cells that synthesize these hormones are rich in smooth ER. Liver cells are another example of specialized cells that contain an abundance of smooth ER. These cells provide an example of the role of smooth ER in carbohydrate metabolism. Liver cells store carbohydrates in the form of glycogen.
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The gamma subunit also seems to function as a protector of the alpha complex, preventing fast renal clearance or proteolytic degradation. It also boosts the specificity on the target and could be involved in the binding of the alpha unit. The whole complex is slightly acidic with a pH(I) of 5, but under a lower pH and/or high ionic strength the subunits dissociate. Just as the PLA2 enzyme the PLA2 toxin is Ca2+ dependent for hydrolysing fatty acyl ester bonds at the sn-2 position of glycerol-phospholipids.
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People with Tangier disease have defective ABCA1 transporters resulting in a greatly reduced ability to transport cholesterol out of their cells, which leads to an accumulation of cholesterol and phospholipids in many body tissues, which can cause them to increase in size. Reduced blood levels of high-density lipoproteins is sometimes described as hypoalphalipoproteinemia. People affected by this condition also have slightly elevated amounts of fat in the blood (mild hypertriglyceridemia) and disturbances in nerve function (neuropathy). The tonsils are visibly affected by this disorder; they frequently appear orange or yellow and are extremely enlarged.
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The binding of vinculin to talin and actin is regulated by polyphosphoinositides and inhibited by acidic phospholipids. The complex then serves to anchor actin filaments to the membrane and thus, helps to reinforce force on talin within the focal adhesions. The loss of vinculin impacts a variety of cell functions; it disrupts the formation of the complex, and prevents cell adhesion and spreading. The absence of the protein demonstrates a decrease in spreading of cells, accompanied by reduced stress fiber formation, formation of fewer focal adhesions, and inhibition of lamellipodia extension.
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Clevidipine will still be rapidly metabolized in pseudocholinesterase-deficient patients. Clevidipine is formulated as a lipid emulsion in 20% soybean oil (Intralipid) and contains approximately 0.2 g of fat per mL (2.0 kcal/ml). Clevidipine also contains glycerin (22.5 mg/mL), purified egg yolk phospholipids (12 mg/mL), and sodium hydroxide to adjust pH. Clevidipine has a pH of 6.0–8.0 In the perioperative patient population Clevidipine produces a 4–5% reduction in systolic blood pressure within 2–4 minutes after starting a 1–2 mg/hour IV infusion.
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The word liposome derives from two Greek words: lipo ("fat") and soma ("body"); it is so named because its composition is primarily of phospholipid. Liposomes were first described by British haematologist Alec D Bangham in 1961 (published 1964), at the Babraham Institute, in Cambridge. They were discovered when Bangham and R. W. Horne were testing the institute's new electron microscope by adding negative stain to dry phospholipids. The resemblance to the plasmalemma was obvious, and the microscope pictures served as the first evidence for the cell membrane being a bilayer lipid structure.
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IP3 is the rate-limiting substrate for the synthesis of inositol polyphosphates, which stimulate multiple protein kinases, transcription, and mRNA processing. Regulation of PLC activity is thus vital to the coordination and regulation of other enzymes of pathways that are central to the control of cellular physiology. Additionally, phospholipase C plays an important role in the inflammation pathway. The binding of agonists such as thrombin, epinephrine, or collagen, to platelet surface receptors can trigger the activation of phospholipase C to catalyze the release of arachidonic acid from two major membrane phospholipids, phosphatidylinositol and phosphatidylcholine.
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Triglycerides are emulsified by bile and hydrolyzed by the enzyme lipase, resulting in a mixture of fatty acids and monoglycerides. These then pass from the intestinal lumen into the enterocyte, where they are re-esterified to form triglycerides. The triglycerides are then combined with phospholipids, cholesteryl esters, and apolipoprotein B-48 to form a nascent chylomicron. These are then released by exocytosis from the enterocytes into the lacteals, lymphatic vessels originating in the villi of the small intestine, and are then secreted into the bloodstream at the thoracic duct's connection with the left subclavian vein.
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There are some hypotheses and models that try to explain the pharmacological effects of phospholipase A2 (PLA2) activity. There is a hypothesis based on the damage that PLA2 does to membrane phospholipids via hydrolysis at the specific binding sites on exocytotically active parts of the membrane. This could lead to interference with the reabsorption of vesicles and the depletion of the acetylcholine store.Montecucco, Cesare, et al (2009). "Different Mechanisms of Inhibition of Nerve Terminals by Botulinum and Snake Presynaptic Neurotoxins", Toxicon, 54(5), 561–564. doi:10.1016/j.toxicon.2008.12.012.
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An example of a biological semi- permeable membrane is the lipid bilayer, on which is based on the plasma membrane that surrounds all biological cells. A group of phospholipids (consisting of a phosphate head and two fatty acid tails) arranged into a double layer, the phospholipid bilayer is a semipermeable membrane that is very specific in its permeability. The hydrophilic phosphate heads are in the outside layer and exposed to the water content outside and within the cell. The hydrophobic tails are the layer hidden in the inside of the membrane.
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The amphipathic nature of saponins gives them activity as surfactants with potential ability to interact with cell membrane components, such as cholesterol and phospholipids, possibly making saponins useful for development of cosmetics and drugs. Saponins have also been used as adjuvants in development of vaccines, such as Quil A, an extract from the bark of Quillaja saponaria. This makes them of interest for possible use in subunit vaccines and vaccines directed against intracellular pathogens. In their use as adjuvants for manufacturing vaccines, toxicity associated with sterol complexation remains a concern.
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In mammals, the SCD-1 reaction requires molecular oxygen, NAD(P)-cytochrome b5 reductase, cytochrome b5 to conduct an electron flow from NADPH to the terminal electron acceptor molecular oxygen, releasing water. Stearoyl-CoA desaturase (Δ-9-desaturase) is an endoplasmic reticulum enzyme that catalyzes the rate-limiting step in the formation of monounsaturated fatty acids (MUFAs), specifically oleate and palmitoleate from stearoyl-CoA and palmitoyl- CoA. Oleate and palmitoleate are major components of membrane phospholipids, cholesterol esters and alkyl-diacylglycerol. In humans, the enzyme is encoded by the SCD gene.
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Upon activation (in platelets) or injury (in erythrocytes, platelets, endothelium, and other cells), certain cells expose the phospholipid phosphatidylserine on their surface and act as catalysts to induce the coagulation cascade. Surface exposure of phosphatidylserine is thought to be brought about by the activation of scramblases. Several enzyme complexes of blood coagulation cascade such as tenase and prothrombinase are activated by the cell surface exposure of the phosphatidylserine. However, the most studied member of the scramblase family PLSCR1 was shown to be defective in translocation of phospholipids when reconstituted into proteoliposomes in vitro.
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Unlike other S-100 proteins, the second EF-hand of protein p11 is incapable of binding calcium due to a series of mutations caused by deletions and substitutions. Annexin II, which is attracted to negatively charged phospholipids, binds to p11 at the Ca2+ binding site. In addition, Annexin II has been implicated in membrane-cytoskeleton interactions and in regulations of ion currents and substances across the membrane. P11 and annexin II form a heterotetrameric protein complex that imitates the structure and function of S-100 proteins activated by the binding of calcium.
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Instead they possess a DHR2 domain which mediates Rac activation by stabilising it in its nucleotide-free state. Dock180-related proteins also possess a DHR1 domain which has been shown, in vitro, to bind phospholipids and which may be involved in their interaction with cellular membranes. Other structural features of Dock180 include an N-terminal SH3 domain involved in binding to ELMO proteins (see below) and a C-terminal proline-rich region which, in Myoblast city (the Drosophila melanogaster ortholog of Dock180), was shown to bind DCrk (the Drosophila ortholog of Crk).
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Cytohesin-1 (CYTH1) is a member of the cytohesin family. Members of this family have identical structural organization that consists of an N-terminal coiled-coil motif, a central Sec7 domain, and a C-terminal pleckstrin homology (PH) domain. The coiled-coil motif is involved in homodimerization, the Sec7 domain contains guanine-nucleotide exchange protein (GEP) activity, and the PH domain interacts with phospholipids and is responsible for association of CYTHs with membranes. Members of this family appear to mediate the regulation of protein sorting and membrane trafficking.
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The biosynthesis for leukotrienes as well as the mechanism of action of cysteinyl leukotriene receptor type 1 antagonists The cysteinyl leukotrienes (LTC4, LTD4, LTE4) are powerful inflammatory inducing eicosanoids that are produced and released by various cells of the immune system. Leukotrienes are produced from arachidonic acid by 5-lipoxygenase (which is made from phospholipids in the cell membrane) and other various enzymes. The cells of the immune system that release leukotrienes are basophils, eosinophils, mast cells and macrophages following various stimuli for example allergens. They bind to cysteinyl leukotriene receptors (CysLT).
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By this route, drugs cross the skin by directly passing through both the phospholipids membranes and the cytoplasm of the dead keratinocytes that constitute the stratum corneum. Although this is the path of shortest distance, the drugs encounter significant resistance to permeation. This resistance is caused because the drugs must cross the lipophilic membrane of each cell, then the hydrophilic cellular contents containing keratin, and then the phospholipid bilayer of the cell one more time. This series of steps is repeated numerous times to traverse the full thickness of the stratum corneum.
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The phospholipid composition of a cell membrane affects the arrangement of cholesterol within the membrane and the ability for CDC to bind and initiate pore-formation. For example, perfringolysin O will preferentially bind to cholesterol-rich membranes composed mainly of phospholipids containing 18-carbon acyl chains. Lipids having a conical molecular shape alter the energetic state of membrane cholesterol, augmenting the interaction of the sterol with the cholesterol-specific cytolysin. Since high cholesterol concentrations are required for CDC binding/pore-formation, it was thought that CDC would associate with lipid rafts.
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In coagulation factors V and VIII the repeated domains compose part of a larger functional domain which promotes binding to anionic phospholipids on the surface of platelets and endothelial cells. The C-terminal domain of the second FA58C repeat (C2) of coagulation factor VIII has been shown to be responsible for phosphatidylserine-binding and essential for activity. FA58C contains two conserved cysteines in most proteins, which link the extremities of the domain by a disulfide bond. A further disulfide bond is located near the C-terminal of the second FA58C domain in MFGM .
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Furthermore, two other human sEH, epoxide hydrolases 3 and 4 (see epoxide hydrolase), have been defined but their role in attacking EETs (and other epoxides) in vivo has not yet been determined. Besides these four epoxide hydrolase pathways, EETs may be acylated into phospholipids in an Acylation-like reaction. This pathway may serve to limit the action of EETs or store them for future release. EETs are also inactivated by being further metabolized though three other pathways: Beta oxidation, Omega oxidation, and elongation by enzymes involved in Fatty acid synthesis.
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400px The majority of early research suggested that the translocation of polycationic CPPs across biological membranes occurred via an energy- independent cellular process. It was believed that translocation could progress at 4 °C and most likely involved a direct electrostatic interaction with negatively charged phospholipids. Researchers proposed several models in attempts to elucidate the biophysical mechanism of this energy-independent process. Although CPPs promote direct effects on the biophysical properties of pure membrane systems, the identification of fixation artifacts when using fluorescent labeled probe CPPs caused a reevaluation of CPP-import mechanisms.
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These dihydroxy-DPAs typically are far less active than their epoxide precursors. The sEH pathway acts rapidly and is by far the predominant pathway of EDP inactivation; its operation causes EDPs to function as short-lived mediators whose actions are limited to their parent and nearby cells, i.e. they are autocrine and paracrine signaling agents, respectively. In addition to the sEH pathway, EDPs, similar to the EETs, may be acylated into phospholipids in an Acylation- like reaction; this pathway may serve to limit the action of EETs or store them for future release.
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Mature spores are spherical, irregularly shaped, and range from 6-10 μ in diameter. Both immature and mature spores can be easily separated from the aleuriophore, which usually ruptures slightly below the point of attachment, so free spores may be found with the top portion still attached. Thermophilic moulds grown at high temperatures (above 50 °C) contain dense body vesicles in their hyphae that function as storage organelles, mainly for phospholipids. In T. lanuginosus, nine times more lipid storage vesicles are grown at 52 °C than 37 °C.
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Detailed diagram of lipid bilayer cell membrane The cell membrane, or plasma membrane, is a biological membrane that surrounds the cytoplasm of a cell. In animals, the plasma membrane is the outer boundary of the cell, while in plants and prokaryotes it is usually covered by a cell wall. This membrane serves to separate and protect a cell from its surrounding environment and is made mostly from a double layer of phospholipids, which are amphiphilic (partly hydrophobic and partly hydrophilic). Hence, the layer is called a phospholipid bilayer, or sometimes a fluid mosaic membrane.
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Lipoprotein-X is a lamellar particle of 30 to 70 nm in diameter as revealed by electron microscopy. It is characterized by its high content of phospholipids (66% by weight) and unesterified cholesterol (22%), and its low content of protein (6%), cholesterol esters (3%), and triglycerides (3%). The protein component is dominated by albumin, located in the core, and by apolipoprotein C, located on the surface of the particle. Using zonal ultracentrifugation, lipoprotein-X can be divided into three distinct populations: Lp-X1, Lp-X2, and Lp-X3, differing in density and apolipoprotein composition.
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The toxicity of ribotoxins results from the combination of their specific catalytic activity and their ability to cross lipid membranes. Since no protein receptor has been found, the lipid composition of these membranes is a determining factor of their cytotoxic activity. Using phospholipid model systems it has been demonstrated that α-sarcin is able to bind to lipid vesicles enriched in acid phospholipids, promoting their aggregation, leading to fusion, and altering their permeability. This allows the protein to be translocated through certain lipid bilayers in absence of any other protein.
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In atherosclerosis, an underlying cause of Coronary artery disease and strokes, atheromatous plaques accumulate in the vascular tunica intima thereby narrowing blood vessel size and decreasing blood flow. In an animal model and in humans 13-HODE (primarily esterified to cholesterol, phospholipids, and possibly other lipids) is a dominant component of these plaques. Since these studies found that early into the progression of the plaques, 13-HODE consisted primarily of the S stereoisomer while more mature plaques contained equal amounts of S and R stereoisomers, it was suggested that 15-LOX-1 contributes to early accumulation while cytochrome and/or free radical pathways contributes to the later accumulation of the plaques. Further studies suggest that 13(S)-HODE contributes to plaque formation by activating the transcription factor, PPARγ (13(R)-HODE lacks this ability), which in turn stimulates the production of two receptors on the surface of macrophages resident in the plaques, 1) CD36, a scavenger receptor for oxidized low density lipoproteins, native lipoproteins, oxidized phospholipids, and long- chain fatty acids, and 2) adipocyte protein 2 (aP2), a fatty acid binding protein; this may cause macrophages to increase their uptake of these lipids, transition to lipid-laden foam cells, and thereby increase plaque size.
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These act as emulsifiers which keep the individual globules from coalescing and protect the contents of these globules from various enzymes in the fluid portion of the milk. Although 97–98% of lipids are triacylglycerols, small amounts of di- and monoacylglycerols, free cholesterol and cholesterol esters, free fatty acids, and phospholipids are also present. Unlike protein and carbohydrates, fat composition in milk varies widely in the composition due to genetic, lactational, and nutritional factor difference between different species. Like composition, fat globules vary in size from less than 0.2 to about 15 micrometers in diameter between different species.
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Cholesterol, glycerophospholipids and sphingolipids are major constituents of the cell membrane and in certain cases function as second messengers in cell proliferation, apoptosis and cell adhesion in inflammation and tumor metastasis. Far-eastern blot was established as a method for transferring lipids from an HPTLC plate to a polyvinylidene difluoride (PVDF) membrane within a minute. Applications of this with other methods have been studied. Far-eastern blotting allows for the purification of glycosphingolipids and phospholipids, structural analysis of lipids in conjunction with direct mass spectrometry, binding studies using various ligands such as antibodies, lectins, bacterium, viruses, and toxins, and enzyme reaction on membranes.
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The blood coagulation and left Factor IX is produced as a zymogen, an inactive precursor. It is processed to remove the signal peptide, glycosylated and then cleaved by factor XIa (of the contact pathway) or factor VIIa (of the tissue factor pathway) to produce a two-chain form, where the chains are linked by a disulfide bridge. When activated into factor IXa, in the presence of Ca2+, membrane phospholipids, and a Factor VIII cofactor, it hydrolyses one arginine-isoleucine bond in factor X to form factor Xa. Factor IX is inhibited by antithrombin. Factor IX expression increases with age in humans and mice.
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Prodan is a fluorescent dye (a naphthalene derivative) used as a membrane probe with environment-sensitive coloration, as well as a non-covalently bonding probe for proteins. Prodan was proposed as a membrane dye by Weber and Farris in 1979. Since then, multiple deivatives have been introduced, such as lypophilic Laurdan (derivative of lauric acid) and thiol-reactive Badan (bromoacetic acid derivative) and Acrylodan. Being a push-pull dye, Prodan has a large excited-state dipole moment and consequently high sensibility to the polarity of its environment (solvent or cell membrane, including the physical state of surrounding phospholipids).
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Pyridoxine (vitamin B6) is required in increased amounts because it is needed to produce amino acids. Vitamin B12 is an AAFCO-recommended vitamin that is essential in the metabolism of carbohydrates and protein and maintains a healthy nervous system, healthy mucous membranes, healthy muscle and heart function, and, in general, promotes normal growth and development. Choline is also a AAFCO recommended ingredient for kittens, which is important for neurotransmission in the brain and as a component of membrane phospholipids. Biotin is another AAFCO-recommended vitamin to support thyroid and adrenal glands and the reproductive and nervous systems.
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However, most accepted scientific models build on the Miller–Urey experiment and the work of Sidney Fox, which show that conditions on the primitive Earth favored chemical reactions that synthesize amino acids and other organic compounds from inorganic precursors, and phospholipids spontaneously form lipid bilayers, the basic structure of a cell membrane. Living organisms synthesize proteins, which are polymers of amino acids using instructions encoded by deoxyribonucleic acid (DNA). Protein synthesis entails intermediary ribonucleic acid (RNA) polymers. One possibility for how life began is that genes originated first, followed by proteins; the alternative being that proteins came first and then genes.
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Cytohesin-4 is a protein that in humans is encoded by the CYTH4 gene. This gene encodes a member of the cytohesin (CYTH) family, formerly known as the PSCD (pleckstrin homology, Sec7 and coiled-coil domains) family. Members of this family have identical structural organization that consists of an N-terminal coiled-coil motif, a central Sec7 domain, and a C-terminal pleckstrin homology (PH) domain. The coiled-coil motif is involved in homodimerization, the Sec7 domain contains guanine-nucleotide exchange protein (GEP) activity, and the PH domain interacts with phospholipids and is responsible for association of CYTHs with membranes.
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It does so in a time-dependent rather than dose-dependent manner, meaning that risk can be minimized by reducing the duration of use. Amikacin causes nephrotoxicity (damage to the kidneys), by acting on the proximal renal tubules. It easily ionizes to a cation and binds to the anionic sites of the epithelial cells of the proximal tubule as part of receptor-mediated pinocytosis. The concentration of amikacin in the renal cortex becomes ten times that of amikacin in the plasma; it then most likely interferes with the metabolism of phospholipids in the lysosomes, which causes lytic enzymes to leak into the cytoplasm.
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It is thus understandable why SM digestion occurs most effectively in the low part of the small intestine, where most fat, phospholipids, and bile salt have been absorbed or up taken. It is also understandable that considerable amount of dietary sphingomyelin is delivered into the colon and excreted in the feces. ENPP7 may have important roles in preventing tumorigenesis in the intestinal tract, as ceramide, the product of sphingomyelin hydrolysis, can inhibit cell proliferation and stimulate cell differentiation and apoptosis. Animal studies showed that supplement of SM or ceramide in the diet may inhibit the development of colon cancer.
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Cytohesin-3 is a protein that in humans is encoded by the CYTH3 gene. This gene encodes a member of the cytohesin (CYTH) family, formerly known as the PSCD (pleckstrin homology, Sec7 and coiled-coil domains) family. Cytohesin family members have identical structural organization that consists of an N-terminal coiled-coil motif, a central Sec7 domain, and a C-terminal pleckstrin homology (PH) domain. The coiled-coil motif is involved in homodimerization, the Sec7 domain contains guanine-nucleotide exchange protein (GEP) activity, and the PH domain interacts with phospholipids and is responsible for association of CYTHs with membranes.
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Cholesterol is also implicated in cell signaling processes, assisting in the formation of lipid rafts in the plasma membrane, which brings receptor proteins in close proximity with high concentrations of second messenger molecules. In multiple layers, cholesterol and phospholipids, both electrical insulators, can facilitate speed of transmission of electrical impulses along nerve tissue. For many neuron fibers, a myelin sheath, rich in cholesterol since it is derived from compacted layers of Schwann cell membrane, provides insulation for more efficient conduction of impulses. Demyelination (loss of some of these Schwann cells) is believed to be part of the basis for multiple sclerosis.
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Cerebral atherosclerosis is a type of atherosclerosis where build-up of plaque in the blood vessels of the brain occurs. Some of the main components of the plaques are connective tissue, extracellular matrix, including collagen, proteoglycans, fibronectin, and elastic fibers; crystalline cholesterol, cholesteryl esters, and phospholipids; cells such as monocyte derived macrophages, T-lymphocytes, and smooth muscle cells. The plaque that builds up can lead to further complications such as stroke, as the plaque disrupts blood flow within the intracranial arterioles. This causes the downstream sections of the brain that would normally be supplied by the blocked artery to suffer from ischemia.
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There are various usages of ethanol which include an additive to gasoline, a primary ingredient for food preservation as well as alcoholic beverages and being used for transdermal drug delivery. For example, it can function as an antiseptic in topical creams to kill bacteria by denaturing proteins. Ethanol is an amphiphilic molecule meaning that it has chemical and physical properties associated with hydrophobic and hydrophilic molecules. Although, studies show that when penetrating through the biomembrane its hydrophobic abilities appear to be limited based on its preference to bind closely to the hydrophilic region of the phospholipids.
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PLA1's are present in numerous species including humans, and have a variety of cellular functions that include regulation and facilitation of the production of lysophospholipid mediators, and acting as digestive enzymes. These enzymes are responsible for fast turnover rates of cellular phospholipids. In addition to this, the products of the reaction catalyzed by PLA1 which are a fatty acid and a lysophospholipid are important in various biological functions such as platelet aggregation and smooth muscle contraction. In addition, lysophospholipids can be found as surfactants in food techniques and cosmetics, and can be used in drug delivery.
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Alpha-synuclein is specifically upregulated in a discrete population of presynaptic terminals of the brain during a period of acquisition-related synaptic rearrangement. It has been shown that alpha- synuclein significantly interacts with tubulin, and that alpha-synuclein may have activity as a potential microtubule-associated protein, like tau. Recent evidence suggests that alpha-synuclein functions as a molecular chaperone in the formation of SNARE complexes. In particular, it simultaneously binds to phospholipids of the plasma membrane via its N-terminus domain and to synaptobrevin-2 via its C-terminus domain, with increased importance during synaptic activity.
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Dock10 shares the same domain arrangement as other members of the DOCK-D/Zizimin subfamily as well as a high level of sequence similarity. It contains a DHR2 domain that is involved in G protein binding and a DHR1 domain, which, in some DOCK family proteins, interacts with membrane phospholipids. Like other DOCK-D subfamily proteins Dock10 contains an N-terminal PH domain, which, in Dock9/Zizimin1, mediates recruitment to the plasma membrane. The DHR2 domain of Dock10 appears to bind to the small G proteins Cdc42, TC10 and TCL although these interactions are of low affinity.
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Like other GDGTs, crenarchaeol is a membrane lipid with distinct hydrophobic and hydrophilic regions. The long, nonpolar hydrocarbon chains are hydrophobic while the ether-linked glycerol head groups are polar and hydrophilic. In most organisms, the cell membrane consists of a lipid bilayer in which phospholipids arrange with their hydrophobic, nonpolar hydrocarbon tails facing inwards towards one another and their hydrophilic, polar head groups facing outwards to associate with the polar environments of the cytoplasm or cell exterior. This organization is promoted by the hydrophobic effect, which makes it energetically favorable for hydrophobic molecules to isolate themselves away from aqueous environments.
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A study conducted in 2016 used primary metabolite profiling through a combination of liquid chromatography and mass spectrometry to identify possible biomarkers for anxiety-related behavior. Primary metabolites are directly involved in more "natural" processes, such as reproduction and development, so abnormal differences could result in differences of mental development. Results identified changes in thirteen metabolites between dogs who had separation anxiety and those who did not; these changes included differences in hypoxanthine, indoxysulfate and phospholipids, all which control oxidative stress, tryptophan levels, and lipid metabolisms. Researchers concluded that biomarkers like primary metabolites play a prominent role in canine anxiety.
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Fatty acid metabolism consists of catabolic processes that generate energy, and anabolic processes that create biologically important molecules (triglycerides, phospholipids, second messengers, local hormones and ketone bodies). Fatty acids are a family of molecules classified within the lipid macronutrient class. One role of fatty acids in animal metabolism is energy production, captured in the form of adenosine triphosphate (ATP). When compared to other macronutrient classes (carbohydrates and protein), fatty acids yield the most ATP on an energy per gram basis, when they are completely oxidized to CO2 and water by beta oxidation and the citric acid cycle.
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A wide range of organisms synthesize polyynes. These chemicals have various biological activities, including as flavorings and pigments, chemical repellants and toxins, and potential application to biomedical research and pharmaceuticals. 8,10-Octadecadiynoic acid The simple fatty acid 8,10-octadecadiynoic acid is isolated from the root bark of the legume Paramacrolobium caeruleum of the family Caesalpiniaceae and has been investigated as a photopolymerizable unit in synthetic phospholipids. Thiarubrine B Thiarubrine B is the most prevalent among several related light-sensitive pigments that have been isolated from the Giant Ragweed (Ambrosia trifida), a plant used in herbal medicine.
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Structure of Milk fat globule membrane in the mammary alveolus Milk fat globule membrane (MFGM) is a complex and unique structure composed primarily of lipids and proteins that surrounds milk fat globule secreted from the milk producing cells of humans and other mammals. It is a source of multiple bioactive compounds, including phospholipids, glycolipids, glycoproteins, and carbohydrates that have important functional roles within the brain and gut. Preclinical studies have demonstrated effects of MFGM-derived bioactive components on brain structure and function, intestinal development, and immune defense. Similarly, pediatric clinical trials have reported beneficial effects on cognitive and immune outcomes.
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This leads to the surrounding of the droplet in a phospholipid monolayer that allows it to disperse within the aqueous cytoplasm. In the next stage, lipid droplets then migrate to the apical surface of the cell, where plasma membrane subsequently envelops the droplet and extrudes together with it. It fully encases the fat droplet in an additional bilayer of phospholipids. The milk fat globule thus released into the glandular lumen, measuring 3-6 μm in average diameter, is surrounded by a phospholipid trilayer containing associated proteins, carbohydrates, and lipids derived primarily from the membrane of the secreting lactocyte.
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Surfactant molecules arranged on an air – water interface Jeewanu protocells are synthetic chemical particles that possess cell-like structure and seem to have some functional living properties. First synthesized in 1963 from simple minerals and basic organics while exposed to sunlight, it is still reported to have some metabolic capabilities, the presence of semipermeable membrane, amino acids, phospholipids, carbohydrates and RNA-like molecules. However, the nature and properties of the Jeewanu remains to be clarified. In a similar synthesis experiment a frozen mixture of water, methanol, ammonia and carbon monoxide was exposed to ultraviolet (UV) radiation.
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Such cooperative interactions between the membrane and its encapsulated contents could greatly simplify the transition from simple replicating molecules to true cells. Furthermore, competition for membrane molecules would favour stabilized membranes, suggesting a selective advantage for the evolution of cross-linked fatty acids and even the phospholipids of today. Such micro-encapsulation would allow for metabolism within the membrane, the exchange of small molecules but the prevention of passage of large substances across it. The main advantages of encapsulation include the increased solubility of the contained cargo within the capsule and the storage of energy in the form of an electrochemical gradient.
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Anemia is common in children with SLE and develops in about 50% of cases. Low platelet count and white blood cell count may be due to the disease or a side effect of pharmacological treatment. People with SLE may have an association with antiphospholipid antibody syndrome (a thrombotic disorder), wherein autoantibodies to phospholipids are present in their serum. Abnormalities associated with antiphospholipid antibody syndrome include a paradoxical prolonged partial thromboplastin time (which usually occurs in hemorrhagic disorders) and a positive test for antiphospholipid antibodies; the combination of such findings have earned the term "lupus anticoagulant- positive".
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A variety of unicellular and colonial freshwater microalgae The chemical composition of microalgae is not an intrinsic constant factor but varies over a wide range, both depending on species and on cultivation conditions. Some microalgae have the capacity to acclimate to changes in environmental conditions by altering their chemical composition in response to environmental variability. A particularly dramatic example is their ability to replace phospholipids with non-phosphorus membrane lipids in phosphorus-depleted environments. It is possible to accumulate the desired products in microalgae to a large extent by changing environmental factors, like temperature, illumination, pH, CO2 supply, salt and nutrients.
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Cells with immune system recognition abilities include macrophages, dentritic cells, T cells, and B cells. Cell–cell recognition is especially important in the innate immune system, which identifies pathogens very generally. Central to this process is the binding of pattern recognition receptors (PRRs) of phagocytes and pathogen-associated molecular patterns (PAMPs) in pathogenic microorganisms. One type of PRR is a group of integral membrane glycoproteins called toll-like receptors (TLRs), which can recognize certain lipoproteins, peptidoglycan, CpG-rich DNA, and flagellar components in bacterial cells, as well as glycoproteins and phospholipids from protozoan parasites and conidia (fungal spores).
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PIP2 and other phosphoinositides are important modifiers of cytoskeletal dynamics and membrane transport and can traffic PLD to its substrate PC. PLDs regulated by these phospholipids are commonly involved in intracellular signal transduction. Their activity is dependent upon the binding of these phosphoinositides near the active site. In plants and animals, this binding site is characterized by the presence of a conserved sequence of basic and aromatic amino acids. In plants such as Arabidopsis thaliana, this sequence is constituted by a RxxxxxKxR motif together with its inverted repeat, where R is arginine and K is lysine.
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Another method involves coating the UCNP in long amphiphilic alkyl chains to create a pseudo bilayer. The hydrophobic tails of the amphiphiles are inserted in between the oleate ligands on the surface of the NP, leaving the hydrophilic heads to face outwards. Phospholipids have been used for this purpose with great success, as they are readily engulfed by biological cells Using this strategy, surface charge is easily controlled by choosing the second layer and some functionalized molecules can be loaded to the outer layer. Both surface charge and surface functional groups are important in bioactivity of nanoparticles.
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Lipoproteins transfer lipids (fats) around the body in the extracellular fluid, making fats available to body cells for receptor-mediated endocytosis. Lipoproteins are complex particles composed of multiple proteins, typically 80–100 proteins per particle (organized by a single apolipoprotein B for LDL and the larger particles). A single LDL particle is about 220–275 angstroms in diameter, typically transporting 3,000 to 6,000 fat molecules per particle, and varying in size according to the number and mix of fat molecules contained within. The lipids carried include all fat molecules with cholesterol, phospholipids, and triglycerides dominant; amounts of each varying considerably.
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Enzymes of the phospholipase C family catalyze the hydrolysis of phospholipids to yield diacylglycerols and water-soluble phosphorylated derivatives of the lipid head groups. A number of these enzymes have specificity for phosphoinositides. Of the phosphoinositide-specific phospholipase C enzymes, C-beta is regulated by heterotrimeric G protein-coupled receptors, while the closely related C-gamma-1 (PLCG1; MIM 172420) and C-gamma-2 enzymes are controlled by receptor tyrosine kinases. The C-gamma-1 and C-gamma-2 enzymes are composed of phospholipase domains that flank regions of homology to noncatalytic domains of the SRC oncogene product, SH2 and SH3.
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Dietary factors likely contribute to insulin resistance, however, causative foods are difficult to determine given the limitations of nutrition research. Foods that have independently been linked to insulin resistance include those high in sugar with high glycemic indices, high in dietary fat and fructose, low in omega-3 and fiber, and which are hyper-palatable which increases risk of overeating. Overconsumption of fat- and sugar-rich meals and beverages have been proposed as a fundamental factor behind the metabolic syndrome epidemic. Diet also has the potential to change the ratio of polyunsaturated to saturated phospholipids in cell membranes.
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Prothrombinase assembly begins with the binding of Factor Xa and Factor Va to negatively charged phospholipids on plasma membranes. Activated Factor Xa and Factor Va bind to the plasma membranes of a variety of different cell types, including monocytes, platelets, and endothelial cells. Both Factor Xa and Va bind to the membrane independently of each other, but they both bind to mutually exclusive binding sites. Both Factor Xa and Factor Va associate with the membrane via their light chains, with Factor Xa binding via its Gla-domain in a calcium- dependent manner and Factor Va via its C2 and C1 domains.
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They are intrinsically disordered proteins, with an acidic pH, with high proportions of alanine, glycine, proline, and glutamic acid. They are membrane-bound through a lipid anchor at the N-terminus, and a polybasic domain in the middle. They are regulated by Ca2+/calmodulin and protein kinase C. In their unphosphorylated form, they bind to actin filaments, causing them to crosslink, and sequester acidic membrane phospholipids such as PIP2. The protein encoded by this gene is a substrate for protein kinase C. It is localized to the plasma membrane and is an actin filament crosslinking protein.
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The primary role of the lipid bilayer in biology is to separate aqueous compartments from their surroundings. Without some form of barrier delineating “self” from “non-self,” it is difficult to even define the concept of an organism or of life. This barrier takes the form of a lipid bilayer in all known life forms except for a few species of archaea that utilize a specially adapted lipid monolayer. It has even been proposed that the very first form of life may have been a simple lipid vesicle with virtually its sole biosynthetic capability being the production of more phospholipids.
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This work led to the establishment of techniques of culture of young ovules and ovaries. This technique has also been used as an additional tool for obtaining improved varieties of rice, wheat, potato and other crops. She has also worked on regeneration of plants and mechanism of regeneration involving various enzymes, membrane phospholipids and second messengers during her time at the School of Life Sciences, Jawaharlal Nehru University, Delhi. Guha-Mukherjee then went to the US in late 1966 and worked with R. S. Bandurski at the Department of Botany and Plant Pathology as a research associate at Michigan State University.
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All of these elements are nonmetals. Sulfur is contained in the amino acids cysteine and methionine. Phosphorus is contained in phospholipids, a class of lipids that are a major component of all cell membranes, as they can form lipid bilayers, which keep ions, proteins, and other molecules where they are needed for cell function, and prevent them from diffusing into areas where they should not be. Phosphate groups are also an essential component of the backbone of nucleic acids (general name for DNA & RNA) and are required to form ATP – the main molecule used as energy powering the cell in all living creatures.
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They perform key roles in lipid metabolism and the conversion of reactive oxygen species. Peroxisomes are involved in the catabolism of very long chain fatty acids, branched chain fatty acids, bile acid intermediates (in the liver), D-amino acids, and polyamines, the reduction of reactive oxygen species – specifically hydrogen peroxide. – and the biosynthesis of plasmalogens, i.e., ether phospholipids critical for the normal function of mammalian brains and lungs They also contain approximately 10% of the total activity of two enzymes (Glucose-6-phosphate dehydrogenase and 6-Phosphogluconate dehydrogenase) in the pentose phosphate pathway , which is important for energy metabolism.
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Cytohesin-2 (CYTH2), formerly known as Pleckstrin homology, Sec7 and coiled/coil domains 2 (PSCD2), is a member of the cytohesin family. Members of this family have identical structural organization that consists of an N-terminal coiled-coil motif, a central Sec7 domain, and a C-terminal pleckstrin homology (PH) domain. The coiled-coil motif is involved in homodimerization, the Sec7 domain contains guanine-nucleotide exchange protein (GEP) activity, and the PH domain interacts with phospholipids and is responsible for association of CYTHs with membranes. Members of this family appear to mediate the regulation of protein sorting and membrane trafficking.
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Instead they possess a DHR2 domain which mediates Rac activation by stabilising it in its nucleotide-free state. They also contain a DHR1 domain which binds phospholipids and is required for the interaction between Dock2 and the plasma membrane. As with other members of the DOCK-A and DOCK-B subfamilies, Dock2 contains an N-terminal SH3 domain which is involved in binding to ELMO proteins (see below). Dock180 contains a C-terminal proline rich region which mediates binding to Crk, however, Dock2 lacks this feature despite the fact that it is able to bind the Crk-like protein CrkL.
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Under longer term flooding, the levels were 27%, 36% and 37% respectively and with total biomass being significantly lower. Dimethyl acetals (DMA) formed during derivatization are considered to be biomarkers of anaerobic bacteria. Archaea are universally distributed in soils and have been shown to control nitrification in acidic conditions and to contribute to ammonia oxidation in agricultural and forest soils. However, as the phospholipids of archaea are not ester linked as in bacteria, but are ether linked, they are not significantly present in routine PLFA sample preparation which is designed to cleave ester-linked fatty acids.
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Tissue factor belongs to the cytokine receptor protein superfamily and consists of three domains: # an extracellular domain, which consists of two fibronectin type III modules whose hydrophobic cores merge in the domain-domain interface. This serves as a (probably rigid) template for factor VIIa binding. # a transmembrane domain. # a cytosolic domain of 21 amino acids length inside the cell which is involved in the signaling function of TF. Note that one of factor VIIa's domains, GLA domain, binds in the presence of calcium to negatively charged phospholipids, and this binding greatly enhances factor VIIa binding to tissue factor.
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Thromboplastin (TPL) or thrombokinase is a mixture of both phospholipids and tissue factor found in plasma aiding blood coagulation through catalyzing the conversion of prothrombin to thrombin. It is a complex enzyme that is found in brain, lung, and other tissues and especially in blood platelets and that functions in the conversion of prothrombin to thrombin in the clotting of blood. Although sometimes used as a synonym for the protein tissue factor (with its official name "Coagulation factor III [thromboplastin, tissue factor]"), this is a misconception. Historically, thromboplastin was a lab reagent, usually derived from placental sources, used to assay prothrombin times (PT).
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Jeewanu (Sanskrit for "particles of life") are synthetic chemical particles that possess cell-like structure and seem to have some functional properties; that is, they are a model of primitive cells, or protocells. It was first synthesised by Krishna Bahadur (20 January 1926 — 5 August 1994), an Indian chemist and his team in 1963. Using photochemical reaction, they produced coacervates, microscopic cell-like spheres from a mixture of simple organic and inorganic compounds. Bahadur named these particles 'Jeewanu' because they exhibit some of the basic properties of a cell, such as the presence of semipermeable membrane, amino acids, phospholipids and carbohydrates.
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Langmuir film consisting of complex phospholipids in liquid-condensed state floating on water subphase, imaged with a Brewster Angle Microscope. A Langmuir–Blodgett (LB) film is a nanostructured system formed when Langmuir films—or Langmuir monolayers (LM)—are transferred from the liquid-gas interface to solid supports during the vertical passage of the support through the monolayers. LB films can contain one or more monolayers of an organic material, deposited from the surface of a liquid onto a solid by immersing (or emersing) the solid substrate into (or from) the liquid. A monolayer is adsorbed homogeneously with each immersion or emersion step, thus films with very accurate thickness can be formed.
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However, fatty acids are also important components of the phospholipids that form the phospholipid bilayers out of which all the membranes of the cell are constructed (the cell wall, and the membranes that enclose all the organelles within the cells, such as the nucleus, the mitochondria, endoplasmic reticulum, and the Golgi apparatus). The "uncombined fatty acids" or "free fatty acids" found in the circulation of animals come from the breakdown (or lipolysis) of stored triglycerides. Because they are insoluble in water, these fatty acids are transported bound to plasma albumin. The levels of "free fatty acids" in the blood are limited by the availability of albumin binding sites.
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Traditional models of coagulation developed in the 1960s envisaged two separate cascades, the extrinsic (tissue factor (TF)) pathway and the intrinsic pathway. These pathways converge to a common point, the formation of the Factor Xa/Va complex which together with calcium and bound on a phospholipids surface, generate thrombin (Factor IIa) from prothrombin (Factor II). A new model, the cell-based model of anticoagulation appears to explain more fully the steps in coagulation. This model has three stages: 1) initiation of coagulation on TF-bearing cells, 2) amplification of the procoagulant signal by thrombin generated on the TF- bearing cell and 3) propagation of thrombin generation on the platelet surface.
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When the probe is in an apolar solvent the shift emission is blue, and a red-shifted emission is observed in polar solvents. Due to its structure and its fluorescence characteristics, Laurdan is very useful in studies about lipid bilayer dynamics, more particularly about cell's plasmatic membrane's dynamics. The hydrophobic tail of the fatty acid allows the solubilization of the dye in the lipid bilayer, while the naphthalene moiety of the molecule stays at the level of the glycerol backbones of the membrane’s phospholipids. This means that the fluorescent part of the molecule is located towards the aqueous environment, which makes the reorientation of the solvent dipoles by Laurdan’s emission possible.
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The exact value of the adhesion force of a spatula varies with the surface energy of the substrate to which it adheres. Recent studies have moreover shown that the component of the surface energy derived from long-range forces, such as van der Waals forces, depends on the material's structure below the outermost atomic layers (up to 100 nm beneath the surface); taking that into account, the adhesive strength can be inferred. Apart from the setae, phospholipids—fatty substances produced naturally in their bodies—also come into play. These lipids lubricate the setae and allow the gecko to detach its foot before the next step.
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Different species that infect different host plants have differences in external morphology, for example, oil palm (Elaeis guineensis) infecting Phytomonas exhibit fewer twists than those in coconut (Cocos nucifera). Like other trypanosomatids, the cell surface of Phytomonas species can be divided into the three regions of body surface, flagellar surface, and the flagellar pocket. Also like other trypanosomatids, Phytomonas does not have a cell wall, but instead are protected from host responses and environmental conditions by membrane-anchored proteins and glycoinositol phospholipids. The pelicullar cell membrane is also lined with microtubules that run along the longitudinal axis of the organism, with a single row of 4 microtubules in the flagellar pocket.
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Dinogunellins are unusual phospholipids having a nucleotide instead of the typical glycerol in their structure. They consist of an adenine nucleotide, with a 2-aminosuccinimide attached to the phosphorus moiety and a fatty acid attached to the oxygen from either the C2' or the C3' of the sugar moiety. The fatty acid chain could be either the eicosapentaenoic acid (Dinogunellin-A and Dinogunellin-B) or the stearidonic acid (Dinogunellin-C and Dinogunellin-D). In consequence, Dinogunellin-A and Dinogunellin-B have the same molecular formula (C34H49N8O9P) and molecular weight (744.8 g/mol), an so do Dinogunellin-C and Dinogunellin-D (C32H47N8O9P; 718.7 g/mol).
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Facilitated diffusion in the cell membrane, showing ion channels (left) and carrier proteins (three on the right). Facilitated diffusion is the passage of molecules or ions across a biological membrane through specific transport proteins and requires no energy input. Facilitated diffusion is used especially in the case of large polar molecules and charged ions; once such ions are dissolved in water they cannot diffuse freely across cell membranes due to the hydrophobic nature of the fatty acid tails of the phospholipids that make up the bilayers. The type of carrier proteins used in facilitated diffusion is slightly different from those used in active transport.
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The thickness of the biomembrane determines the permeability of the membrane and ethanol, which can be used as a solvent, is able to reduce the thickness of the biomembrane which is one way this amphiphilic molecule is able to permeate through the biomembrane. There can also be free energy changes that can increase or decrease during the phase transitions of the phospholipids during polymorphism or mesmorphism which can also affect the curvature of lipids. All lipids can experience some sort of positive or negative alternating or spontaneous curvature due to variations in sizes between the hydrophobic and the hydrophilic region.Digging Deeper the Surfactant; Accessed: February 2, 2009.
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Schematic of how the addition of ethanol induces non-lamellar phases; hexaganol(I) and hexagonal(II) versus the lamellar phase described as the bilayer on top of bilayer. Below the schematic is an example of how the hydrophilic region (head group) can be larger or smaller than the hydrophobic region (acyl chains) which affects the curvature as well as the phase of the phospholipid. When lipids are extracted or isolated from biomembranes, Polymorphism and mesomorphism can occur because they are then no longer under the intermolecular constraints that are present within the biomembrane. This can lead to formation of non-lamellar (non-bilayer) or lamellar phases in phospholipids.
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He has pursued the application of photovoltaic polymers to solar energy, and was instrumental in forming the Victorian Organic Solar Cell Consortium. He has also continued to develop new syntheses of novel, biologically-useful materials. An example is his groups' synthesis of phosphoinositides, amphiphilic phospholipids situated in the cell membrane, which collaborators at the Ludwig Institute for Cancer Research have used to probe the dynamics of signal transduction (intercellular signalling being an important component of many aspects of cell biology, including that of tumors). Holmes has served on the editorial or advisory boards of numerous learned scientific journals, including Organic Letters, Chemical Communications and Angewandte Chemie.
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Entry mechanisms for noroviruses are still largely unknown, but the first proteinaceous receptor mediating norovirus entry was found with experiments on MNV. This receptor, CD300lf, is a membrane glycoprotein, that functions in regulation of multiple immune responses. CD300lf is found on mast cells of both murine species and humans, but definite proof of its function in human norovirus infections remains unknown. In mice however, CD300lf functions in virus binding thus having a role to play in the first steps of viral entry. Binding is essentially mediated by phospholipids of the virus' VP1 protein that bind to a cleft between CDR3 and CC’loop -domains of CD300lf -receptor.
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A proteomics approach using two-dimensional chromatography-mass spectrometry found major phospholipids were archaeol phosphatidylglycerol, archaeol phosphatidylinositol, hydroxyarchaeol phosphatidylglycerol, and hydroxyarchaeol phosphatidylinositol. All phospholipid classes contained a series of unsaturated analogues, with the degree of unsaturation dependent on phospholipid class. The proportion of unsaturated lipids from cells grown at 4 °C was significantly higher than for cells grown at 23 °C. 3-Hydroxy-3-methylglutaryl coenzyme A synthase, farnesyl diphosphate synthase, and geranylgeranyl diphosphate synthase were identified in the expressed proteome, and most genes involved in the mevalonate pathway and processes leading to the formation of phosphatidylinositol and phosphatidylglycerol were identified in the genome sequence.
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Arachidonic acid inflammatory cascade Azerizin is claimed to be a proprietary blend of the natural ingredients nicotinamide, azelaic acid, quercetin and curcumin that purportedly combine the anti-inflammatory and antimicrobial properties, along with inhibiting effects on sebum production. The cascade of events in the inflammatory pathway that result from cell membrane disruption is well documented. The release of membrane phospholipids leads to increased production of arachidonic acid which in turn results in elevated leukotriene, prostaglandin and thromboxane production. The ingredients in Azerizin are known to inhibit each of these three major paths of inflammation by blocking or down-regulating pro-inflammatory catalysts at multiple points in the inflammatory cascade, e.g.
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Dock11 exhibits the same domain arrangement as other members of the DOCK-D/Zizimin subfamily and shares the highest level of sequence identity with Dock9. It contains a DHR2 domain which mediates GEF activity and a DHR1 domain which may interact with membrane phospholipids. It also contains an N-terminal PH domain which may be involved in its recruitment to the plasma membrane. Dock11 binds and activates nucleotide-free Cdc42 via its DHR2 domain and has also been reported to mediate positive feedback on active, GTP-bound Cdc42, although this interaction required a small N-terminal region of Dock11 in addition to the DHR2 domain.
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Since the active sites of each catalytic domain are separated by a distance of 40 Å, they are not believed to allosterically effect one another. In contrast, the linker domain is composed of α helices supplied by the two catalytic domains: each domain contributes five helices from their N termini and one from a helix that spans both the catalytic domain and the linker domain. At the center of the linker domain resides an 8 by 35 Å hydrophobic tunnel with two phospholipids bound at each end. The head of each phospholipid points outward towards solution while the tails are embedded within the enzyme.
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Schematic of typical gram-negative cell wall showing arrangement of N-Acetylglucosamine and N-Acetylmuramic acid and the outer membrane containing lipopolysaccharide. The gram-negative cell wall contains a thinner peptidoglycan layer adjacent to the cytoplasmic membrane than the gram-positive wall, which is responsible for the cell wall's inability to retain the crystal violet stain upon decolourisation with ethanol during Gram staining. In addition to the peptidoglycan layer the gram-negative cell wall also contains an additional outer membrane composed by phospholipids and lipopolysaccharides which face into the external environment. The highly charged nature of lipopolysaccharides confer an overall negative charge to the gram -negative cell wall.
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In humans, fatty acids are formed from carbohydrates predominantly in the liver and adipose tissue, as well as in the mammary glands during lactation. The cells of the central nervous system probably also make most of the fatty acids needed for the phospholipids of their extensive membranes from glucose, as blood-born fatty acids cannot cross the blood brain barrier to reach these cells. However, how the essential fatty acids, which mammals cannot synthesize themselves, but are nevertheless important components of cell membranes (and other functions described above) reach them is unknown. The pyruvate produced by glycolysis is an important intermediary in the conversion of carbohydrates into fatty acids and cholesterol.
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Aker BioMarine produces krill products rich in omega-3 phospholipids. Krill is mainly used for the production of krill meal and krill oil, which in turn is used for animal or aquaculture feed and for human consumption through health products and omega-3 supplements. The company has registered Superba as the company’s brand name for nutraceuticals and Qrill as the company’s brand name for its krill meal and krill oil products for aquaculture. As for research, a 2009 study of Superba krill oil found that it gave a substantially larger reduction of fat in the heart and the liver than omega-3 from fish oil.
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Action of bile salts in digestion Recycling of the bile Bile or gall acts to some extent as a surfactant, helping to emulsify the lipids in food. Bile salt anions are hydrophilic on one side and hydrophobic on the other side; consequently, they tend to aggregate around droplets of lipids (triglycerides and phospholipids) to form micelles, with the hydrophobic sides towards the fat and hydrophilic sides facing outwards. The hydrophilic sides are negatively charged, and this charge prevents fat droplets coated with bile from re-aggregating into larger fat particles. Ordinarily, the micelles in the duodenum have a diameter around 1–50 μm in humans.
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Plant lipid transfer proteins, also known as plant LTPs or PLTPs, are a group of highly-conserved proteins of about 7-9kDa found in higher plant tissues. As its name implies, lipid transfer proteins are responsible for the shuttling of phospholipids and other fatty acid groups between cell membranes. LTPs are divided into two structurally related subfamilies according to their molecular masses: LTP1s (9 kDa) and LTP2s (7 kDa). Various LTPs bind a wide range of ligands, including fatty acids (FAs) with a C10–C18 chain length, acyl derivatives of coenzyme A (CoA), phospho- and galactolipids, prostaglandin B2, sterols, molecules of organic solvents, and some drugs.
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407-413 were isolated, transformed plants with gain or loss of function were selected and identified. Advances in the knowledge of the regulation of the biosynthesis of sterols and their derivatives (esters, glucosides) as well as their functions have been obtained.Pascaline Ullmann, Pierrette Bouvier-Navé et Pierre Benveniste, « Regulation by phospholipids and kinetic studies of plant membrane-bound UDP- glucose sterol ß-D-glucosyltransferase », Plant Physiol., 85, 1987, p. 51-55 Work focused on three enzyme systems: epoxide of squalene triterpene synthase,Tania Husselstein-Muller, Hubert Schaller, and Pierre Benveniste, « Molecular cloning and expression in yeast of 2,3-oxidosqualene-triterpenoid cyclases from Arabidopsis thaliana », Plant Mol. Biol.
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In mice, group III sPLA2 are involved in sperm maturation, and group X are thought to be involved in sperm capacitation. sPLA2 has been shown to promote inflammation in mammals by catalyzing the first step of the arachidonic acid pathway by breaking down phospholipids, resulting in the formation of fatty acids including arachidonic acid. This arachidonic acid is then metabolized to form several inflammatory and thrombogenic molecules. Excess levels of sPLA2 is thought to contribute to several inflammatory diseases, and has been shown to promote vascular inflammation correlating with coronary events in coronary artery disease and acute coronary syndrome, and possibly leading to acute respiratory distress syndrome and progression of tonsillitis.
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Cell spreading and movement occur through the process of binding of cell surface integrin receptors to extracellular matrix adhesion molecules. Vinculin is associated with focal adhesion and adherens junctions, which are complexes that nucleate actin filaments and crosslinkers between the external medium, plasma membrane, and actin cytoskeleton. The complex at the focal adhesions consists of several proteins such as vinculin, α-actinin, paxillin, and talin, at the intracellular face of the plasma membrane. In more specific terms, the amino- terminus of vinculin binds to talin, which, in turn, binds to β-integrins, and the carboxy-terminus binds to actin, phospholipids, and paxillin-forming homodimers.
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Monounsaturated fatty acids, the products of SCD-1 catalyzed reactions, can serve as substrates for the synthesis of various kinds of lipids, including phospholipids, triglycerides, and can also be used as mediators in signal transduction and differentiation. Because MUFAs are heavily utilized in cellular processes, variation in SCD activity in mammals is expected to influence physiological variables, including cellular differentiation, insulin sensitivity, metabolic syndrome, atherosclerosis, cancer, and obesity. SCD-1 deficiency results in reduced adiposity, increased insulin sensitivity, and resistance to diet-induced obesity. Under non-fasting conditions, SCD-1 mRNA is highly expressed in white adipose tissue, brown adipose tissue, and the Harderian gland.
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The biological functions of lipid asymmetry are imperfectly understood, although it is clear that it is used in several different situations. For example, when a cell undergoes apoptosis, the phosphatidylserine — normally localised to the cytoplasmic leaflet — is transferred to the outer surface: There, it is recognised by a macrophage that then actively scavenges the dying cell. Lipid asymmetry arises, at least in part, from the fact that most phospholipids are synthesised and initially inserted into the inner monolayer: those that constitute the outer monolayer are then transported from the inner monolayer by a class of enzymes called flippases. Other lipids, such as sphingomyelin, appear to be synthesised at the external leaflet.
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Type II alveolar cells have many important functions in the lung, including the production of pulmonary surfactant, maintenance of fluid balance and composition in the airspace. Phospholipids that make up pulmonary surfactant are broken down by macrophages, releasing phosphate into the alveolar lining fluid. The loss of the Npt2b phosphate transported eliminates the ability of alveolar type II cells to pump phosphorus ions from the alveolar space back into the bloodstream, and leads to microlith formation. Epithelial deletion of Npt2b in mice results in an authentic mimic of the human condition, including accumulation of calcium phosphate microliths in the lung tissue and progressive diffuse radiographic opacities.
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Blood coagulation and the protein C anticoagulation pathway Protein C is a major component in anticoagulation in the human body. It acts as a serine protease zymogen: APC proteolyses peptide bonds in activated Factor V and Factor VIII (Factor Va and Factor VIIIa), and one of the amino acids in the bond is serine. These proteins that APC inactivates, Factor Va and Factor VIIIa, are highly procoagulant cofactors in the generation of thrombin, which is a crucial element in blood clotting; together they are part of the prothrombinase complex. Cofactors in the inactivation of Factor Va and Factor VIIIa include protein S, Factor V, high-density lipoprotein, anionic phospholipids and glycosphingolipids.
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The inner mitochondrial membrane contains proteins with three types of functions: # Those that perform the electron transport chain redox reactions # ATP synthase, which generates ATP in the matrix # Specific transport proteins that regulate metabolite passage into and out of the mitochondrial matrix It contains more than 151 different polypeptides, and has a very high protein-to-phospholipid ratio (more than 3:1 by weight, which is about 1 protein for 15 phospholipids). The inner membrane is home to around 1/5 of the total protein in a mitochondrion. Additionally, the inner membrane is rich in an unusual phospholipid, cardiolipin. This phospholipid was originally discovered in cow hearts in 1942, and is usually characteristic of mitochondrial and bacterial plasma membranes.
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Using this approach, lipids may be divided into eight categories: fatty acids, glycerolipids, glycerophospholipids, sphingolipids, saccharolipids, and polyketides (derived from condensation of ketoacyl subunits); and sterol lipids and prenol lipids (derived from condensation of isoprene subunits). Although the term "lipid" is sometimes used as a synonym for fats, fats are a subgroup of lipids called triglycerides. Lipids also encompass molecules such as fatty acids and their derivatives (including tri-, di-, monoglycerides, and phospholipids), as well as other sterol-containing metabolites such as cholesterol. Although humans and other mammals use various biosynthetic pathways both to break down and to synthesize lipids, some essential lipids can't be made this way and must be obtained from the diet.
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Ann Chim Phys 1844, 10, 434 Several years later, Marcellin Berthelot, one of Pelouze's students, synthesized tristearin and tripalmitin by reaction of the analogous fatty acids with glycerin in the presence of gaseous hydrogen chloride at high temperature.C R Séances Acad Sci, Paris, 1853, 36, 27; Ann Chim Phys 1854, 41, 216 In 1827, William Prout recognized fat ("oily" alimentary matters), along with protein ("albuminous") and carbohydrate ("saccharine"), as an important nutrient for humans and animals. For a century, chemists regarded "fats" as only simple lipids made of fatty acids and glycerol (glycerides), but new forms were described later. Theodore Gobley (1847) discovered phospholipids in mammalian brain and hen egg, called by him as "lecithins".
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The body of Angomonas deanei is elliptical in shape, with a prominent tail-like flagellum at its posterior end for locomotion. The bacterial endosymbiont is inside its body and is surrounded by two membranes typical of Gram-negative bacteria, but its cell membrane presents unusual features, such as the presence of phosphatidylcholine, a major membrane lipid (atypical of bacterial membranes), and the highly reduced peptidoglycan layer, which shows reduced or absence of rigid cell wall. The cell membrane of the protozoan host contains an 18-domain β-barrel porin, which is a characteristic protein of Gram- negative bacteria. In addition it contains cardiolipin and phosphatidylcholine as the major phospholipids, while sterols are absent.
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The hadal zone is the deepest part of the marine environment Marine life decreases with depth, both in abundance and biomass, but there is a wide range of metazoan organisms in the hadal zone, mostly benthos, including fish, sea cucumber, bristle worms, bivalves, isopods, sea anemones, amphipods, copepods, decapod crustaceans and gastropods. Most of these trench communities probably originated from the abyssal plains. Although they have evolved adaptations to high pressure and low temperatures such as lower metabolism, intra-cellular protein-stabilising osmolytes, and unsaturated fatty acids in cell membrane phospholipids, there is no consistent relationship between pressure and metabolic rate in these communities. Increased pressure can instead constrain the ontogenic or larval stages of organisms.
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The MFGM structure is complex and comprises a variety of phospholipids, glycolipids, proteins, and glycoproteins, along with cholesterol and other lipids. Specific lipids and proteins are localized to different layers of the membrane, with carbohydrate chains of glycoproteins and glycolipids directed toward the outer surface of the milk fat globule; the lipid-to-protein weight ratio in MFGM is approximately 1:1. However, the nutritional significance of these components is defined not only by their structure or macronutrient category, but also by the physiological role that each nutrient serves. As a quantitatively minor presence within milk, MFGM likely contributes little to energy production, but its constituents may confer structural and functional benefits.
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The cell membrane is the only cellular structure that is found in all of the cells of all of the organisms on Earth. Researchers Irene A. Chen and Jack W. Szostak (Nobel Prize in Physiology or Medicine 2009) amongst others, demonstrated that simple physicochemical properties of elementary protocells can give rise to simpler conceptual analogues of essential cellular behaviors, including primitive forms of Darwinian competition and energy storage. Such cooperative interactions between the membrane and encapsulated contents could greatly simplify the transition from replicating molecules to true cells. Competition for membrane molecules would favor stabilized membranes, suggesting a selective advantage for the evolution of cross-linked fatty acids and even the phospholipids of today.
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This phase is caused by the packing behavior of single-tail lipids in a bilayer. Although the protocellular self-assembly process that spontaneously form lipid monolayer vesicles and micelles in nature resemble the kinds of primordial vesicles or protocells that might have existed at the beginning of evolution, they are not as sophisticated as the bilayer membranes of today's living organisms. Rather than being made up of phospholipids, however, early membranes may have formed from monolayers or bilayers of fatty acids, which may have formed more readily in a prebiotic environment. Fatty acids have been synthesized in laboratories under a variety of prebiotic conditions and have been found on meteorites, suggesting their natural synthesis in nature.
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An average adult human contains about 0.7 kg of phosphorus, about 85–90% in bones and teeth in the form of apatite, and the remainder in soft tissues and extracellular fluids (~1%). The phosphorus content increases from about 0.5 weight% in infancy to 0.65–1.1 weight% in adults. Average phosphorus concentration in the blood is about 0.4 g/L, about 70% of that is organic and 30% inorganic phosphates. An adult with healthy diet consumes and excretes about 1–3 grams of phosphorus per day, with consumption in the form of inorganic phosphate and phosphorus-containing biomolecules such as nucleic acids and phospholipids; and excretion almost exclusively in the form of phosphate ions such as and .
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In some 3FTx proteins with a C-terminal extension, these residues also participate in forming key binding interactions. The cardiotoxin/cytolysin 3FTx subgroup has a somewhat different set of functionally significant residues due to its distinct mechanism of action, likely involving interactions with phospholipids in the cell membrane, as well as possible functionally significant interactions with other cell- surface molecules such as glycosaminoglycans. A hydrophobic patch of residues contiguous in tertiary structure but distributed over all three loops has been identified as functionally significant in combination with a set of conserved lysine residues conferring local positive charge. Because of their structural similarity and functional diversity, 3FTx proteins have been used as model systems for the study of protein engineering.
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The common effects of the genome shrinking between this endosymbiont and the other parasites are the reduction of the ability to produce phospholipids, repair and recombination and an overall conversion of the composition of the gene to a richer A-T content due to mutation and substitutions. Evidence of the deletion of the function of repair and recombination is the loss of the gene recA, gene involved in the recombinase pathway. This event happened during the removal of a larger region containing ten genes for a total of almost 10 kb. Same faith occurred uvrA, uvrB and uvrC, genes encoding for excision enzymes involved in the repair damaged DNA due to UV exposure.
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A tiny copepod crustacean, Leptocaris stromatolicolus, is known only from the interstices of these stromatolites and bottom sediments in the saline pools. The pools are an oligotrophic environment with little available phosphate, leading one local bacterial species, Bacillus coahuilensis, to acquire the genes necessary to partially replace its membrane phospholipids with sulfolipids through horizontal gene transfer. Several environmental conservation leaders are working to protect the valley, including Pronatura Noreste. The organization owns a private reserve, called Pozas Azules, and has several ongoing projects that include the protection of native species, including stromatolites and the eradication of invasive flora and fauna, as well as community development and water efficient agriculture combined with organic techniques.
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Eicosanoid biosynthesis begins when a cell is activated by mechanical trauma, ischemia, other physical perturbations, attack by pathogens, or stimuli made by nearby cells, tissues, or pathogens such as chemotactic factors, cytokines, growth factors, and even certain eicosanoids. The activated cells then mobilize enzymes, termed phospholipase A2's (PLA2s), capable of releasing ω-6 and ω-3 fatty acids from membrane storage. These fatty acids are bound in ester linkage to the SN2 position of membrane phospholipids; PLA2s act as esterases to release the fatty acid. There are several classes of PLA2s with type IV cytosolic PLA2s (cPLA2s) appearing to be responsible for releasing the fatty acids under many conditions of cell activation.
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Note ether at first position, and acetyl group at second position. In an organic chemistry general sense, an ether lipid implies an ether bridge between an alkyl group (a lipid) and an unspecified alkyl or aryl group, not necessarily glycerol. If glycerol is involved, the compound is called a glyceryl ether, which may take the form of an alkylglycerol, an alkyl acyl glycerol, or in combination with a phosphatide group, a phospholipid. In a biochemical sense, an ether lipid usually implies glycerophospholipids of various type, also called phospholipids, in which the sn-1 position of the glycerol backbone has a lipid attached by an ether bond and a lipid attached to the sn-2 position via an acyl group.
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This protein circulates in the bloodstream in an inactive form, bound to another molecule called von Willebrand factor, until an injury that damages blood vessels occurs. In response to injury, coagulation factor VIII is activated and separates from von Willebrand factor. The active protein (sometimes written as coagulation factor VIIIa) interacts with another coagulation factor called factor IX. This interaction sets off a chain of additional chemical reactions that form a blood clot. Factor VIII participates in blood coagulation; it is a cofactor for factor IXa, which, in the presence of Ca2+ and phospholipids, forms a complex that converts factor X to the activated form Xa. The factor VIII gene produces two alternatively spliced transcripts.
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In the cell, Sec14p plays an active and regulatory role in the intracellular transport of proteins. A good example of this function is the ability of Sec14p to both transport the phospholipids PtdIns and PtdCho between membranes as well as the inhibition of phospholipase D1 and phospholipase B1, which convert PtdCho to phosphatidic acid and choline or PtdCho to glycerophosphocholine, respectively. Sec14p and its homologs, some of which exhibit activation of phospholipase D1 and B1, aid in phospholipid metabolism regulation in vivo. Additionally, Sec14p is essential in the budding of vesicles from the Golgi body, as it is thought to serve a function related to preserving diacylglycerol concentration in the Golgi body, a compound essential to secretory vesicle biosynthesis.
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This is why α-sarcin, the most representative member of the group, was originally discovered as an antitumoural agent. However, it turned out not to be as safe as needed and the research in this field was temporarily abandoned. One of the determining factors in this process of entry into cells appears to be their ability to interact with phospholipids whose polar headgroup shows a net negative electrical charge. Today it is known that ribotoxins constitute a broad family, produced by many types of fungi, with common characteristics that make them optimal candidates to be used for biotechnological purposes, such as pest control, and for the development of anti-cancer drugs in the form of immunotoxins.
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They can be taken up from the blood by all cells that have mitochondria (with the exception of the cells of the central nervous system). Fatty acids can only be broken down in mitochondria, by means of beta-oxidation followed by further combustion in the citric acid cycle to CO2 and water. Cells in the central nervous system, although they possess mitochondria, cannot take free fatty acids up from the blood, as the blood-brain barrier is impervious to most free fatty acids, excluding short-chain fatty acids and medium-chain fatty acids. These cells have to manufacture their own fatty acids from carbohydrates, as described above, in order to produce and maintain the phospholipids of their cell membranes, and those of their organelles.
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This protein is crucial in the transport of phospholipids – and therefore DPPC – to the lamellar bodies of the alveolar cells, where DPPC interacts with surfactant proteins to form pulmonary surfactant. Current studies cannot find a correlation between the percentage of DPPC in lung surfactant and the age of gestation, although a proven relationship has been found between the percentage of DPPC and POPC (palmitoyl-oleoyl phosphatidylcholine) in babies with respiratory distress syndrome compared with babies without this condition. These connections suggest that a particular surfactant composition will lead to respiratory distress syndrome, regardless of gestational age. The correlation between DPPC percentage and respiratory distress syndrome is why DPPC is used to make drugs to treat newborn infants with the disease.
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Group II K antigens closely resemble those in gram-positive bacteria and greatly differ in composition and are further subdivided according to their acidic components, generally 20–50% of the CPS chains are bound to phospholipids. In total there are 60 different K antigens that have been recognized (K1, K2a/ac, K3, K4, K5, K6, K7 (=K56), K8, K9 (=O104), K10, K11, K12 (K82), K13(=K20 and =K23), K14, K15, K16, K18a, K18ab (=K22), K19, K24, K26, K27, K28, K29, K30, K31, K34, K37, K39, K40, K41, K42, K43, K44, K45, K46, K47, K49 (O46), K50, K51, K52, K53, K54 (=K96), K55, K74, K84, K85ab/ac (=O141), K87 (=O32), K92, K93, K95, K97, K98, K100, K101, K102, K103, KX104, KX105, and KX106).
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Cross-sectional view of the structures that can be formed by phospholipids in an aqueous solution A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates cell from the external environment or creates intracellular compartments. Biological membranes, in the form of eukaryotic cell membranes, consist of a phospholipid bilayer with embedded, integral and peripheral proteins used in communication and transportation of chemicals and ions. The bulk of lipid in a cell membrane provides a fluid matrix for proteins to rotate and laterally diffuse for physiological functioning. Proteins are adapted to high membrane fluidity environment of lipid bilayer with the presence of an annular lipid shell, consisting of lipid molecules bound tightly to surface of integral membrane proteins.
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Sewer joined the faculty of the Georgia Institute of Technology in 2002, where she studied how cytochrome P450 enzymes regulate the production of steroid hormones. She received tenure in 2008 before moving to the University of California, San Diego (UCSD) in 2009, where she rose to the rank of full professor in 2015. In addition to teaching pharmacology, she led a lab at the Skaggs School of Pharmacy and Pharmaceutical Sciences researching how lipid metabolism is regulated and how this affects cells. She discovered that nuclear receptors are targets for a type of lipids called sphingolipids and that specific sphingolipids and phospholipids could act as endogenous (natural) ligands (binding partners) for an important regulator of steroid hormone biosynthesis called steroidogenic factor 1 (SF-1).
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In seabirds, primaquine has been used in a study to show effective treatment on infected hosts. Treatment for babesiosis consisted of primaquine (1 mg/kg PO q24h for 10 days; primaquine phosphate 1.76%m/v in stabilized solution, Primaquin Solution, MedPet Ltd, Benrose, South Africa). After, treatment was followed by a phospholipid supplement (1 capsule/bird PO q24h for 12 days; deoiled, enriched phospholipids from soybeans, 300 mg/capsule, Essentiale Extreme, Sanofi Aventis Ltd, Midrand, South Africa); as an attempt to mitigate potential hepatotoxic effects of primaquine. To prevent transmission of Babesia and other tickborne pathogens, all birds with visible ectoparasites are treated with pesticide powder (carbaryl 50 g/kg) upon admission, and the facilities are thoroughly cleaned on a daily basis.
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Mabel's assistant, Ken Sadeghian, worked with her from the 1960s until her retirement. Interest in the PI effect waned in the 1960s and 1970s, but experienced a resurgence in the 1980s due to advances in technology and understanding of cell membrane biochemistry. Mabel and Lowell became regarded as founders of an important and still growing field of biochemistry and cell biology — the many roles of inositol phospholipids in cell function — for which they were honored at a 1996 symposium at the University of Wisconsin that gathered their colleagues from around the world. Their early work was highlighted in a 20th anniversary review of the discovery of inositol-1,4,5-trisphosphate as a second messenger, and their 1953 and 1958 JBC articles were celebrated as "JBC Classics" in 2005.
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They are the main part of plant membrane lipids where they substitute phospholipids to conserve phosphate for other essential processes. These chloroplast membranes contain a high quantity of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). They probably also assume a direct role in photosynthesis, as they have been found in the X-ray structures of photosynthetic complexes. Galactolipids are more bioavailable than free fatty acids, and have been shown to exhibit COX mediated anti-inflammatory activity.Christensen, L. Galactolipids as Potential Health Promoting Compounds in Vegetable Foods Recent Patents on Food, Nutrition & Agriculture, 2009; 1, 50-58. Bio-guided fractionation of spinach leaves (Spinacia oleracea) revealed alpha-linolenic acid galactolipids (18:3, n-3) were responsible for inhibitory effects on tumor promoter-induced Epstein-Barr virus (EBV) activation.
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Cross Section view of the structures that can be formed by phospholipids in aqueous solutions Polymorphism in biophysics is the ability of lipids to aggregate in a variety of ways, giving rise to structures of different shapes, known as "phases". This can be in the form of sphere of lipid molecules (micelles), pairs of layers that face one another (lamellar phase, observed in biological systems as a lipid bilayer), a tubular arrangement (hexagonal), or various cubic phases (Fdm, Imm, Iam, Pnm, and Pmm being those discovered so far). More complicated aggregations have also been observed, such as rhombohedral, tetragonal and orthorhombic phases. It forms an important part of current academic research in the fields of membrane biophysics (polymorphism), biochemistry (biological impact) and organic chemistry (synthesis).
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The founding members of the 3FP family are the three- finger toxins (3FTx) often found in snake venom. 3FTx proteins are widely distributed in venomous snake families, but are particularly enriched in the family Elapidae, in which the relative proportion of 3FTx to other venom toxins can reach 95%. Many 3FTx proteins are neurotoxins, though the mechanism of toxicity varies significantly even among proteins of relatively high sequence identity; common protein targets include those involved in cholinergic signaling, such as the nicotinic acetylcholine receptors, muscarinic acetylcholine receptors, and acetylcholinesterase. Another large subfamily of 3FTx proteins is the cardiotoxins (also known as cytotoxins or cytolysins); this group is directly cytotoxic most likely due to interactions with phospholipids and possibly other components of the cell membrane.
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There are various types of phospholipids; consequently, their synthesis pathways differ. However, the first step in phospholipid synthesis involves the formation of phosphatidate or diacylglycerol 3-phosphate at the endoplasmic reticulum and outer mitochondrial membrane. The synthesis pathway is found below: Phosphatidic acid synthesis The pathway starts with glycerol 3-phosphate, which gets converted to lysophosphatidate via the addition of a fatty acid chain provided by acyl coenzyme A. Then, lysophosphatidate is converted to phosphatidate via the addition of another fatty acid chain contributed by a second acyl CoA; all of these steps are catalyzed by the glycerol phosphate acyltransferase enzyme. Phospholipid synthesis continues in the endoplasmic reticulum, and the biosynthesis pathway diverges depending on the components of the particular phospholipid.
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Some types of phospholipid can be split to produce products that function as second messengers in signal transduction. Examples include phosphatidylinositol (4,5)-bisphosphate (PIP2), that can be split by the enzyme Phospholipase C into inositol triphosphate (IP3) and diacylglycerol (DAG), which both carry out the functions of the Gq type of G protein in response to various stimuli and intervene in various processes from long term depression in neurons to leukocyte signal pathways started by chemokine receptors. Phospholipids also intervene in prostaglandin signal pathways as the raw material used by lipase enzymes to produce the prostaglandin precursors. In plants they serve as the raw material to produce Jasmonic acid, a plant hormone similar in structure to prostaglandins that mediates defensive responses against pathogens.
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Once secretory proteins are formed, the ER membrane separates them from the proteins that will remain in the cytosol. Secretory proteins depart from the ER enfolded in the membranes of vesicles that bud like bubbles from the transitional ER. These vesicles in transit to another part of the cell are called transport vesicles. An alternative mechanism for transport of lipids and proteins out of the ER are through lipid transfer proteins at regions called membrane contact sites where the ER becomes closely and stably associated with the membranes of other organelles, such as the plasma membrane, Golgi or lysosomes. In addition to making secretory proteins, the rough ER makes membranes that grows in place from the addition of proteins and phospholipids.
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Gαi)-Gβγ) complexes) as well as Gα12-Gβγ complexes while the EP3γ isoform activates in addition to and the Gαi\- Gβγ complexes Gαi\- Gβγ complexes. (G protein linkages for the other EP3 isoforms have not been defined.) In consequence, complexes dissociate into Gαi, Gα12, Gs and Gβγ components which proceed to activate cell signaling pathways that lead functional responses viz., pathways that activate phospholipase C to convert cellular phospholipids to diacylglycerol which promotes the activation of certain isoforms of protein kinase C, pathways that elevated cellular cytosolic Ca2+ which thereby regulate Ca2+-sensitive cell signaling molecules, and pathways that inhibit adenyl cyclase which thereby lowers cellular levels of cyclic adenosine monophosphate (cAMP) to reduce the activity of cAMP-dependent signaling molecules.
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It has been found that growth of Gram-negative bacteria in 20 mM Mg reduces the number of protein-to-lipopolysaccharide bonds by increasing the ratio of ionic to covalent bonds, which increases membrane fluidity, facilitating transformation. The role of lipopolysaccharides here are verified from the observation that shorter O-side chains are more effectively transformed – perhaps because of improved DNA accessibility. The surface of bacteria such as E. coli is negatively charged due to phospholipids and lipopolysaccharides on its cell surface, and the DNA is also negatively charged. One function of the divalent cation therefore would be to shield the charges by coordinating the phosphate groups and other negative charges, thereby allowing a DNA molecule to adhere to the cell surface.
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An evaporative light scattering detector (ELSD) is a detector used in conjunction with high-performance liquid chromatography (HPLC), Ultra high- performance liquid chromatography (UHPLC), Purification liquid chromatography such as flash or preparative chromatography, countercurrent or centrifugal partition chromatographies and Supercritical Fluid chromatography (SFC). It is commonly used for analysis of compounds where UV detection might be a restriction and therefore used where compounds do not efficiently absorb UV radiation, such as sugars, antivirals, antibiotics, fatty acids, lipids, oils, phospholipids, polymers, surfactants, terpenoids and triglycerides. ELSDs is related to the charged aerosol detector (CAD) and like the CAD, falls under the category of destructive detectors. An evaporative light scattering detector (ELSD) is able to detect all compound which are less volatile than the mobile phase, i.e.
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They are responsible for aiding the movement of phospholipid molecules between the two leaflets that compose a cell's membrane (transverse diffusion, also known as a "flip-flop" transition). The possibility of active maintenance of an asymmetric distribution of molecules in the phospholipid bilayer was predicted in the early 1970s by Mark Bretscher. Although phospholipids diffuse rapidly in the plane of the membrane, their polar head groups cannot pass easily through the hydrophobic center of the bilayer, limiting their diffusion in this dimension. Some flippases - often instead called scramblases \- are energy-independent and bidirectional, causing reversible equilibration of phospholipid between the two sides of the membrane, whereas others are energy- dependent and unidirectional, using energy from ATP hydrolysis to pump the phospholipid in a preferred direction.
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Clinical studies have repeatedly shown that even though insulin resistance is usually associated with obesity, the membrane phospholipids of the adipocytes of obese patients generally still show an increased degree of fatty acid unsaturation. This seems to point to an adaptive mechanism that allows the adipocyte to maintain its functionality, despite the increased storage demands associated with obesity and insulin resistance. A study conducted in 2013 found that, while INSIG1 and SREBF1 mRNA expression was decreased in the adipose tissue of obese mice and humans, the amount of active SREBF1 was increased in comparison with normal mice and non-obese patients. This downregulation of INSIG1 expression combined with the increase of mature SREBF1 was also correlated with the maintenance of SREBF1-target gene expression.
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In enzymology, a sn-glycerol-1-phosphate dehydrogenase () is an enzyme that catalyzes the chemical reaction :sn-glycerol 1-phosphate + NAD(P)+ \rightleftharpoons glycerone phosphate + NAD(P)H + H+ The 3 substrates of this enzyme are sn-glycerol 1-phosphate, NAD+, and NADP+, whereas its 4 products are glycerone phosphate, NADH, NADPH, and H+. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is sn-glycerol-1-phosphate:NAD(P)+ 2-oxidoreductase. This enzyme is also called glycerol-1-phosphate dehydrogenase [NAD(P)+]. G-1-P dehydrogenase is responsible for the formation of sn-glycerol 1-phosphate, the backbone of the membrane phospholipids of Archaea.
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They found that basic amino alcohols are ideally suited for this purpose, probably because amino groups effectively solvate phospholipids and basicity helps to preserve fluorescence signal. Amino alcohols have also beneficial effect when used for clearing of other tissues, which are mostly highly vascularized, and their opacity is given by absorption of light by hemoglobin on top of light scattering. Amino alcohols reduce pigmentation of those tissues very effectively by eluting the hem from hemoglobin. The original protocol is two- step incubation of fixed tissue in two different aqueous based clearing solutions, altogether taking one to two weeks. First solution, referred as ScaleCUBIC-1, CUBIC-1 or just reagent-1, is composed of N,N,N’,N’-tetrakis(2-hydroxypropyl)ethylenediamine (commercially under name Quadrol), urea and Triton X-100 in water.
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Cholesterol, given that it composes about 30% of all animal cell membranes, is required to build and maintain membranes and modulates membrane fluidity over the range of physiological temperatures. The hydroxyl group of each cholesterol molecule interacts with water molecules surrounding the membrane, as do the polar heads of the membrane phospholipids and sphingolipids, while the bulky steroid and the hydrocarbon chain are embedded in the membrane, alongside the nonpolar fatty-acid chain of the other lipids. Through the interaction with the phospholipid fatty-acid chains, cholesterol increases membrane packing, which both alters membrane fluidity and maintains membrane integrity so that animal cells do not need to build cell walls (like plants and most bacteria). The membrane remains stable and durable without being rigid, allowing animal cells to change shape and animals to move.
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Since free-radical-induced and singlet-oxygen-induced oxidations of linoleic acid produce a similar set of 13-HODE metabolites (see 13-Hydroxyoctadecadienoic acid), since both free radicals and singlet oxygen attack not only free linoleic acid but also linoleic acid bound to phospholipids, glycerides, cholesterol, and other lipids, and since free- radical and singlet-oxygen reactions may occur together, oxygen-stressed tissues often contain an array of free and lipid-bound 9-HODE and 13-HODE products. For example, laboratory studies find that 9-HODE and 9-EE-HODE (along with their 13-HODE counterparts) are found in the phospholipid and cholesterol components of low-density lipoproteins that have been oxidized by human monocytes; the reaction appears due to the in situ free-radical- and/or superoxide-induced oxidation of the lipoproteins.
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Souvenaid is a medical food in the form of a thick, yogurt-like drink that is marketed as helping people with Alzheimer's disease. It contains a mixture of docosahexaenoic acid, eicosapentaenoic acid, phospholipids, choline, uridine monophosphate, vitamin E (alpha-tocopherol equivalents), selenium, vitamin B12, vitamin B6, and folic acid; this mixture is branded as Fortasyn Connect. As of 2017, the product had failed to show a significant effect in decreasing the rate of cognitive decline or delaying progression of Alzheimer's disease, but appeared to cause minor improvement in verbal memory in some people in the very early stages of the disease. The clinical trials that had been conducted were in people with very early Alzheimer's disease and excluded people who ate recommended amounts of food that included fish oil.
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The discovery that a hormone can influence phosphoinositide metabolism was made by Mabel R. Hokin (1924–2003) and her then husband Lowell E. Hokin in 1953, when they discovered that radioactive 32P phosphate was incorporated into the phosphatidylinositol of pancreas slices when stimulated with acetylcholine. Up until then phospholipids were believed to be inert structures only used by cells as building blocks for construction of the plasma membrane. Over the next 20 years, little was discovered about the importance of PIP2 metabolism in terms of cell signaling, until the mid-1970s when Robert H. Michell hypothesized a connection between the catabolism of PIP2 and increases in intracellular calcium (Ca2+) levels. He hypothesized that receptor-activated hydrolysis of PIP2 produced a molecule that caused increases in intracellular calcium mobilization.
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Lamellar phase refers generally to packing of polar-headed long chain nonpolar-tail molecules in an environment of bulk polar liquid, as sheets of bilayers separated by bulk liquid. In biophysics, polar lipids (mostly, phospholipids, and rarely, glycolipids) pack as a liquid crystalline bilayer, with hydrophobic fatty acyl long chains directed inwardly and polar headgroups of lipids aligned on the outside in contact with water, as a 2-dimensional flat sheet surface. Under transmission electron microscope (TEM), after staining with polar headgroup reactive chemical osmium tetroxide, lamellar lipid phase appears as two thin parallel dark staining lines/sheets, constituted by aligned polar headgroups of lipids. 'Sandwiched' between these two parallel lines, there exists one thicker line/sheet of non-staining closely packed layer of long lipid fatty acyl chains.
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NAPE-PLD is an enzyme activity - a phospholipase, acting on phospholipids found in the cell membrane. It is not homology but the chemical outcome of its activity that classes it as phospholipase D. The enzymatic activity was discovered and characterized in a series of experiments culminating in the 2004 publication of a biochemical purification scheme from which peptide sequencing could be accomplished. Researchers homogenized (finely ground) hearts from 150 rats and subjected the resulting crude lysate to sucrose sedimentation at 105,000 x g to separate out the cell membranes from the remainder of the cell. The integral membrane proteins were then solubilized using octyl glucoside and subjected to four column chromatography steps (HiTrap SP HP cation-exchange column, HiTrap Q anion-exchange column, HiTrap Blue affinity column, Bio-Gel HTP hydroxyapatite column).
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Scott syndrome is a rare congenital bleeding disorder that is due to a defect in a platelet mechanism required for blood coagulation.Weiss HJ. Scott syndrome: a disorder of platelet coagulant activity (PCA). Sem Hemat 1994; 31:312-319 Normally when a vascular injury occurs, platelets are activated and phosphatidylserine (PS) in the inner leaflet of the platelet membrane is transported to the outer leaflet of the platelet membrane, where it provides a binding site for plasma protein complexes that are involved in the conversion of prothrombin to thrombin, such as factor VIIIa-IXa (tenase) and factor Va-Xa (prothrombinase).Zwaal FA, Comfurius P, Bevers EM. Scott syndrome, a bleeding disorder caused by defective scrambling of membrane phospholipids. Biochem Bioph Acta 2004; 1636:119-128 In Scott syndrome, the mechanism for translocating PS to the platelet membrane is defective, resulting in impaired thrombin formation.
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Although the endosomal compartment is composed of vesicular and tubular structures, it has been demonstrated that sorting involving recycling pathways is mainly tubule-mediated. Therefore, tubular structures building is essential for the activity of SNXs containing BAR domains (such as SNX1, SNX4 or SNX8) as phosphoinositide-mediated endosomal sorting proteins. This BAR domain allows them to assembly in a dose-dependent manner a helical coat with the capacity to detect, promote and stabilize the curvature of endosomal vesicular membranes into tubular profiles during the so-called incidence detection process, specially in phosphoinosited-enriched regions where they are localized thanks to the affinity of the PX domain for these membrane phospholipids. In particular, SNX8 colocalizes with Rab5 at early endosomes membranes and at the tubular endosomal network (TEN) around the endosomal vacuole, which is an important compartment for successful sorting of cargoes.
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The division of coagulation in two pathways is arbitrary, originating from laboratory tests in which clotting times were measured either after the clotting was initiated by glass, the intrinsic pathway; or clotting was initiated by thromboplastin (a mix of tissue factor and phospholipids), the extrinsic pathway. Further, the final common pathway scheme implies that prothrombin is converted to thrombin only when acted upon by the intrinsic or extrinsic pathways, which is an oversimplification. In fact, thrombin is generated by activated platelets at the initiation of the platelet plug, which in turn promotes more platelet activation. Thrombin functions not only to convert fibrinogen to fibrin, it also activates Factors VIII and V and their inhibitor protein C (in the presence of thrombomodulin); and it activates Factor XIII, which forms covalent bonds that crosslink the fibrin polymers that form from activated monomers.
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Oxidation of fatty acids Fatty acids (mainly in the form of triglycerides) are therefore the foremost storage form of fuel in most animals, and to a lesser extent in plants. In addition, fatty acids are important components of the phospholipids that form the phospholipid bilayers out of which all the membranes of the cell are constructed (the plasma membrane and other membranes that enclose all the organelles within the cells, such as the nucleus, the mitochondria, endoplasmic reticulum, and the Golgi apparatus). Fatty acids can also be cleaved, or partially cleaved, from their chemical attachments in the cell membrane to form second messengers within the cell, and local hormones in the immediate vicinity of the cell. The prostaglandins made from arachidonic acid stored in the cell membrane, are probably the most well known group of these local hormones.
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The exact mechanism by which PEMT catalyzes the sequential methylation of PE by three molecules of SAM to form PC remains unknown. Kinetic analyses as well as amino acid and gene sequencing have shed some light on how the enzyme works. Studies suggest that a single substrate binding site binds all three phospholipids methylated by PEMT: PE, phosphatidyl-monomethylethanolamine (PMME) and phosphatidyl- dimethylethanolamine. The first methylation, that of PE to PMME, has been shown to be the rate-limiting step in conversion of PE to PC. It is suspected that the structure or specific conformation adopted by PE has a lower affinity for the PEMT active site; consequently, upon methylation, PMME would be immediately converted to PDME and PDME to PC, via a Bi-Bi or ping-pong mechanism before another PE molecule could enter the active site.
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The kinase (CR3) domain of human Raf kinases is inhibited by two mechanisms: autoinhibition by its own regulatory Ras-GTP-binding CR1 domain and a lack of post-translational phosphorylation of key serine and tyrosine residues (S338 and Y341 for c-Raf) in the CR2 hinge region. During B-Raf activation, the protein's autoinhibitory CR1 domain first binds Ras-GTP's effector domain to the CR1 Ras-binding domain (RBD) to release the kinase CR3 domain like other members of the human Raf kinase family. The CR1-Ras interaction is later strengthened through the binding of the cysteine-rich subdomain (CRD) of CR1 to Ras and membrane phospholipids. Unlike A-Raf and C-Raf, which must be phosphorylated on hydroxyl-containing CR2 residues before fully releasing CR1 to become active, B-Raf is constituitively phosphorylated on CR2 S445.
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The choice of liposome preparation method depends, i.a., on the following parameters: # the physicochemical characteristics of the material to be entrapped and those of the liposomal ingredients; # the nature of the medium in which the lipid vesicles are dispersed # the effective concentration of the entrapped substance and its potential toxicity; # additional processes involved during application/delivery of the vesicles; # optimum size, polydispersity and shelf-life of the vesicles for the intended application; and, # batch-to-batch reproducibility and possibility of large- scale production of safe and efficient liposomal products Useful liposomes rarely form spontaneously. They typically form after supplying enough energy to a dispersion of (phospho)lipids in a polar solvent, such as water, to break down multilamellar aggregates into oligo- or unilamellar bilayer vesicles. Liposomes can hence be created by sonicating a dispersion of amphipatic lipids, such as phospholipids, in water.
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The binding and pore formation of CDC will occur when the concentration of cholesterol exceeds the association capacity of the phospholipids, allowing the excess cholesterol to associate with the toxin. The presence of cholesterol aggregates in an aqueous solution were sufficient to initiate a conformation change and oligomerization of perfringolysin O (PFO), while no changes were seen by perfingolysin O with epicholesterol aggregates in solution. Epicholesterol is a sterol that differs from cholesterol by the orientation of the 3-β-OH group, which is axial in epicholesterol and equatorial in cholesterol. Since the orientation of the hydroxyl group has such an effect on the bind/pore-formation of CDC, the equatorial conformation may be required for docking of the sterol to the binding pocket in domain 4, or to be properly exposed at the surface of lipid structures.
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The ratio of NLFA concentration to PLFA concentration (active mycelia) can then give the proportion of carbon allocated to storage structures (spores, measured as NLFA). Problems with lipid fatty acid analyses include the incomplete specificity of fatty acids to AM fungi, the species- or genera-specific variation in fatty acid composition can complicate analysis in systems with multiple AM fungal species (e.g. field soil), the high background levels of certain fatty acid concentration in soils, and that phospholipids are correlated to an organism's membrane area, and the surface to volume ratio can vary widely between organisms such as bacteria and fungi. More work must be done to identify the efficacy of this method in field soils with many genera and species of AM fungi to discern the methods ability to discriminate between many varying fatty acid compositions.
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The three main structures phospholipids form in solution; the liposome (a closed bilayer), the micelle and the bilayer. In 1954 and 1958 Krishna Bahadur and co-workers published the successful synthesis of amino acids from a mixture of paraformaldehyde, colloidal molybdenum oxide or potassium nitrate and ferric chloride under sunlight. It appears that this experimental approach was seminal for the assays to produce Jeewanu, which he first reported in 1963 in an obscure Indian journal, Vijnana Parishad Anusandhan Patrika. His detailed syntheses were published in Germany in 1964 in a series of articles. Their initial experiment consisted of a sterilised apparatus in which inorganic nitrogenous compounds (such as ammonium phosphate and ammonium molybdate) and organic compounds such as citric acid (C6H8O7), paraformaldehyde (OH(CH2O)nH) and formaldehyde (CH2O) for carbon sources were mixed with minerals commonly found in living cells.
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15-lipoxygenase 1 (ALOX15), while best known for converting the 20 carbon polyunsaturated fatty acid, arachidonic acid, into a series of 15-hydroxylated arachidonic acid metabolites (see 15-hydroxyicosatetraenoic acid), actually prefers as its substrate the 18 carbon polyunsaturated fatty acid, linoleic acid, over arachidonic acid, converting it to 13-hydroperoxy-9Z,11E-octadecadienoic acid (13-HpODE). The enzyme acts in a highly stereospecific manner, forming 13(S)-hydroperoxy-9Z,11E-octadecadienoic acid (13(S)-HpODE) but comparatively little or no 13(R)-hydroperoxy-9Z,11E-octadecadienoic acid (13(R)-HpODE) -. In cells, 13(S)-HpODE is rapidly reduced by peroxidases to 13(S)-HODE. ALOX15 is fully capable of metabolizing the linoleic acid that is bound to phospholipid or cholesterol to form 13(S)-HpODE-bound phospholipids and cholesterol that are rapidly converted to their corresponding 13(S)-HODE-bound products.
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MUFAs (especially oleic acid) have been found to lower the incidence of insulin resistance PUFAs (especially large amounts of arachidonic acid) and SFAs (such as arachidic acid) increased it. These ratios can be indexed in the phospholipids of human skeletal muscle and in other tissues as well. This relationship between dietary fats and insulin resistance is presumed secondary to the relationship between insulin resistance and inflammation, which is partially modulated by dietary fat ratios (Omega-3/6/9) with both omega 3 and 9 thought to be anti- inflammatory, and omega 6 pro-inflammatory (as well as by numerous other dietary components, particularly polyphenols and exercise, with both of these anti-inflammatory). Although both pro- and anti-inflammatory types of fat are biologically necessary, fat dietary ratios in most US diets are skewed towards Omega 6, with subsequent disinhibition of inflammation and potentiation of insulin resistance.
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The term may also be used more broadly as a synonym of lipid -- any substance of biological relevance, composed of carbon, hydrogen, or oxygen, that is insoluble in water but soluble in non-polar solvents. In this sense, besides the triglycerides, the term would include several other types of compounds like mono- and diglycerides, phospholipids (such as lecithin), sterols (such as cholesterol), waxes (such as beeswax), and free fatty acids, which are usually present in human diet in smaller amounts. Fats are one of the three main macronutrient groups in human diet, along with carbohydrates and proteins, and the main components of common food products like milk, butter, tallow, lard, bacon, and cooking oils. They are a major and dense source of food energy for many animals and play important structural and metabolic functions, in most living beings, including energy storage, waterproofing, and thermal insulation.
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In 2003 Nissen led a Journal of the American Medical Association study, producing evidence that five weekly infusions of ApoA-I Milano/phospholipids complex, a synthetic form of HDL, can possibly remove significant amounts of plaque from coronary arteries. The lipoprotein enhanced the ability of HDL, or “good” cholesterol to usher fat out of the arteries and into the liver for excretion leading to the purchase of Esperion Therapeutics, the tiny company that had produced recombinant Apo-A1 Milano, by Pfizer for $1.3 billion. Also in 2005, Nissen published the results of the REVERSAL trial, a headto-head comparison of the statins atorvastatin (Lipitor) and pravastatin (Pravachol). IVUS images showed that Lipitor had effectively halted the progression of plaque buildup, but coronary disease progressed considerably in those given Pravachol. The study suggested that treatments should aim to lower LDL, or “bad” cholesterol levels as much as possible.
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Starting with oleic acid (1), which possesses a cis double bond at the carbon 9 position from desaturation and a bound of phospholipids (-PL), a bifunctional desaturase/acetylnase system occurred with oxygen (a) to introduce the second cis double bond at the carbon 12 position to form linoleic acid (2). This step was then repeated to turn the cis double bond at the carbon 12 position into a triple bond (also called acetylenic bond) to form crepenynic acid (3). Crepenynic acid was reacted with oxygen (b) to form a second cis double bond at the carbon 14 position (conjugated position) leading to the formation of dehydrocrepenynic acid (4). Allylic isomerization (c) was responsible for the changes from the cis double bond at the carbon 14 position into the triple bond (5) and formation of the more favored trans (E) double bond at the carbon 17 position (6).
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The phospholipids that comprise the outer membrane give it the same semi-permeable characteristics as the cytoplasmic membrane The porin channel is partially blocked by a loop, called the eyelet, which projects into the cavity. In general, it is found between strands 5 and 6 of each barrel, and it defines the size of solute that can traverse the channel. It is lined almost exclusively with charged amino acyl residues arranged on opposite sides of the channel, creating a transversal electric field across the pore. The eyelet has a local surplus of negative charges from four glutamic acid and seven aspartic acid residues (in contrast to one histidine, two lysine and three arginine residues) is partially compensated for by two bound calcium atoms, and this asymmetric arrangement of molecules is thought to have an influence in the selection of molecules that can pass through the channel[3].
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When the signal is received and acted on, negative feedback is provided to the receptor that stops the need for further signaling. The cannabinoid receptor type 1 (CB1), located at the presynaptic neuron, is a receptor that can stop stressful neurotransmitter release to the postsynaptic neuron; it is activated by endocannabinoids (ECs) such as anandamide (N-arachidonoylethanolamide; AEA) and 2-arachidonoylglycerol (2-AG) via a retrograde signaling process in which these compounds are synthesized by and released from postsynaptic neurons, and travel back to the presynaptic terminal to bind to the CB1 receptor for modulation of neurotransmitter release to obtain homeostasis. The polyunsaturated fatty acids (PUFAs) are lipid derivatives of omega-3 (docosahexaenoic acid, DHA, and eicosapentaenoic acid, EPA) or of omega-6 (arachidonic acid, ARA) are synthesized from membrane phospholipids and used as a precursor for endocannabinoids (ECs) mediate significant effects in the fine-tune adjustment of body homeostasis.
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The REIMS method is unique, in that, while the above-described mass spectrometry techniques specific to the particular method developed ion sources should be used, but it is difficult in the case of ion source devices used in surgical practice. With the operation of a variety of tissue-cutting tools, such as a diathermy knife, a surgical laser, or an ultrasonic tissue atomizer, an aerosol is formed having a composition characteristic of the tissue cut, which also contains ionized cell constructs. Among them, in terms of using the REIMS method, the intact membrane-forming phospholipids are important, which easily are detectable by mass spectrometry on the one hand, and on the other hand, contain the combination of the characteristics of the particular tissue type. Mass spectrometric analysis is just one implementation of an effective extraction system development that was needed to cut the surgical site at the time of running the generated aerosol mass spectrometer.
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The linoleic acid metabolites, 9(S)-hydroxyoctadecadienoic acid (HODE), (9R)-HODE, and 13(R)-HODE (see 9-Hydroxyoctadecadienoic acid and 13-Hydroxyoctadecadienoic acid), and the arachidonic acid metabolites 5(S)-hydroxyicosatetraenoic acid (see 5-HETE), 12(S)-HETE (see 12-HETE), 15(S)-HETE (see 15-hydroxyicosatetraenoic acid), and racemic 5-HETE, 12-HETE, 15-HETE, 8-HETE, 9-HETE, and 11-HETE stimulate Chinese hamster ovary cells made to express G2A; these effects, unlike those of phospholipids, appear to involve and require the binding of the metabolites to G2A as evidenced by the ability of the most potent of these metabolites, 9-HODE to stimulate G2A-dependent functions in membranes isolated from these cells. 9-HODE induces cultured normal human epidermal keratinocytes to stop growing by inhibiting their cell cycle at the G1 stage; it also stimulates these cells to secrete three cytokines that stimulate keratinocyte growth vis., interleukin-6, interleukin-8, and GM-CSF. These activities are G2A-dependent.
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Through systematic and careful labeling- and enzyme activity studies in the 1980s and 90s, he was able to demonstrate several previously unknown biochemical pathways for oil production in seeds and which later proved to be true for plant cells in general. Later in his career, Stymne focused on studying the biochemical processes involved in the biosynthesis of exotic fatty acids, an area where Sten have had great impact by increasing the knowledge of how specialized acyltransferases and phospholipases are essential for the enrichment of exotic fatty acids in the oil. Furthermore, Stymne's group could identify and describe a whole new plant family of enzymes (PDATs) previously identified only in animals and responsible for transferring fatty acids between phospholipids and diacylglycerol molecules which play an important role in oil synthesis not only in plants but at all higher organisms. Stymne's group was also the first to clone and characterize plant genes for membrane lipid synthesis (LPCATs) and synthesis of sterol esters (PSAT).
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SNX8 protein regulates cholesterol levels as an activator of the SREBPs (Sterol Regulatory Element Binding Proteins), which is a family of transcription factors that control the expression of enzymes needed for the synthesis and uptake of fatty acids, endogenous cholesterol, triacylglycerides and phospholipids; this results in an overall regulation of intracellular lipid homeostasis. Although its precise mechanism of action remains unknown, data suggests that SNX8 produces changes in cholesterol distribution through regulation of the SREBP transcriptional activity by modulating intracellular traffic events rather than by interacting with proteins of the SREBP pathway like INSIG or SREBP cleavage-activating protein (SCAP). For example, it is unclear if SNX8 has a direct participation in the transport of SREBP pathway components or if it regulates endosomal and lysosomal compartimentalisation through the production of cholesterol cargoes. This last possibility is supported by the fact that the ability of altering membrane curvature is shared by some proteins of the SNXs family.
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The sequence is divided up into codons, each of which is a particular sequence of three nucleotides and corresponds to a particular amino acid. Thus a sequence of DNA codes for a particular protein that, due to the chemical properties of the amino acids it is made from, folds in a particular manner and so performs a particular function. These protein functions have been recognized: # Enzymes, which catalyze all of the reactions of metabolism # Structural proteins, such as tubulin, or collagen # Regulatory proteins, such as transcription factors or cyclins that regulate the cell cycle # Signaling molecules or their receptors such as some hormones and their receptors # Defensive proteins, which can include everything from antibodies of the immune system, to toxins (e.g., dendrotoxins of snakes), to proteins that include unusual amino acids like canavanine A bilayer of phospholipids makes up the membrane of cells that constitutes a barrier, containing everything within the cell and preventing compounds from freely passing into, and out of, the cell.
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The experimental method and analytical technique is quite different. In the previous study, it emphasized the NNR technique using a set of host phospholipids, exchanging lipids, ethanol, and cholesterol to create model membranes. An aqueous solution containing 5% ethanol (v/v) was maintained but the concentration of cholesterol was varied to prove how this sterol compound can inhibit the effects of ethanol (inducing a liquid-disorder phase or non-lamellar phases) which is depicted in the different plots of the equilibrium constant (K) versus the mol% of cholesterol for each model membrane. In this study, phospholipid membrane is comparable to the model membrane which consists of POPC, ethanol, water and in some cases the addition of monovalent ions (Na+, K+, and Cl−) that are transported throughout the membrane in the presence of ethanol. The concentration of ethanol varies ranging from 2.5 to 30 mol% in an aqueous solution but there is no addition of any sterol compound.
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When such cells are activated, arachidonic acid is liberated from cell membrane phospholipids by phospholipase A2, and donated by the 5-lipoxygenase-activating protein (FLAP) to 5-lipoxygenase. 5-Lipoxygenase (5-LO) uses FLAP to convert arachidonic acid into 5-hydroperoxyeicosatetraenoic acid (5-HPETE), which spontaneously reduces to 5-hydroxyeicosatetraenoic acid (5-HETE). The enzyme 5-LO acts again on 5-HETE to convert it into leukotriene A4 (LTA4), an unstable epoxide. 5-HETE can be further metabolized to 5-oxo-ETE and 5-oxo-15-hydroxy-ETE, all of which have pro-inflammatory actions similar but not identical to those of LTB4 and mediated not by LTB4 receptors but rather by the OXE receptor (see 5-Hydroxyicosatetraenoic acid and 5-oxo-eicosatetraenoic acid). In cells equipped with LTA hydrolase, such as neutrophils and monocytes, LTA4 is converted to the dihydroxy acid leukotriene LTB4, which is a powerful chemoattractant for neutrophils acting at BLT1 and BLT2 receptors on the plasma membrane of these cells.
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Gram-positive bacteria has a similar component named Lipoteichoic acid, or LTA. HDL has the ability to bind LPS and LTA, creating HDL-LPS complexes to neutralize the harmful effects in the body and clear the LPS from the body. HDL also has significant roles interacting with cells of the immune system to modulate the availability of cholesterol and modulate the immune response. Under certain abnormal physiological conditions such as system infection or sepsis, the major components of HDL become altered, The composition and quantity of lipids and apolipoproteins are altered as compared to normal physiological conditions, such as a decrease in HDL cholesterol (HDL-C), phospholipids, apoA-I (a major lipoprotein in HDL that has been shown to have beneficial anti-inflammatory properties), and an increase in Serum amyloid A. This altered composition of HDL is commonly referred to as acute- phase HDL in an acute-phase inflammatory response, during which time HDL can lose its ability to inhibit the oxidation of LDL.
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It is possible that the exposure of cholesterol at the membrane surface might be facilitated by other membrane- damaging toxins secreted such as phospholipase C, which cleave the head groups of phospholipids increasing the exposure of cholesterol. Two organisms, Clostridium perfringens that produces perfringolysin O (CDC) and α-toxin during clostridial myonecrosis and Listeria monocytogenes which releases listeriolysin O (CDC) and phospholipases C leading to the virulence of these bacteria. However, although the C. perfringens α-toxin treatment of liposome membranes increase the activity of PFO on those membranes this affect does not appear to aways be the case "in vivo". During C. perfringens gas gangrene (myonecrosis) the main site of action of the C. perfringens α-toxin is the muscle tissue, where the cleavage of the phospholipid head groups does not seem to increase the activity of perfringolysin O on this tissue, as knockouts of PFO do not appear to significantly alter the course of the myonecrosis.
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In the maturation of the red blood cell lineage (see erythropoiesis) from mitochondria-bearing reticulocytes to mature mitochondria-free erythrocytes in rabbits, the mitochondria accumulate phospholipid-bound 13(S)-HODE in their membranes due to the action of a lipoxygenase which (in rabbits, mice, and other sub-primate vertebrates) directly metabolizes linoleic acid-bound phospholipid to 13(S)-HpODE-bound phospholipid which is rapidly reduced to 13(S)-HODE-bound phospholipid. It is suggested that the accumulation of phospholipid-bound 13(S)-HpODE and/or 13(S)-HODE is a critical step in rendering mitochondria more permeable thereby triggering their degradation and thence maturation to erythrocytes. However, functional inactivation of the phospholipid-attacking lipoxygenase gene in mice does not cause major defects in erythropoiesis. It is suggested that mitochondrial degradation proceeds through at least two redundant pathways besides that triggered by lipoxygenase-dependent formation of 13(S)-HpODE- and 13(S)-HODE-bound phospholipids viz.
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Prostaglandin-endoperoxide synthase (PTGS), also known as cyclooxygenase (COX), is the key enzyme in prostaglandin biosynthesis. It converts free arachidonic acid, released from membrane phospholipids at the sn-2 ester binding site by the enzymatic activity of phospholipase A2, to prostaglandin (PG) H2. The reaction involves both cyclooxygenase (dioxygenase) and hydroperoxidase (peroxidase) activity. The cyclooxygenase activity incorporates two oxygen molecules into arachidonic acid or alternate polyunsaturated fatty acid substrates, such as linoleic acid and eicosapentaenoic acid. Metabolism of arachidonic acid forms a labile intermediate peroxide, PGG2, which is reduced to the corresponding alcohol, PGH2, by the enzyme’s hydroperoxidase activity. While metabolizing arachidonic acid primarily to PGG2, COX-1 also converts this fatty acid to small amounts of a racemic mixture of 15-Hydroxyicosatetraenoic acids (i.e., 15-HETEs) composed of ~22% 15(R)-HETE and ~78% 15(S)-HETE stereoisomers as well as a small amount of 11(R)-HETE. The two 15-HETE stereoisomers have intrinsic biological activities but, perhaps more importantly, can be further metabolized to a major class of anti-inflammatory agents, the lipoxins.
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Most 2H-NMR experiments with deuterated phospholipids demonstrate that the presence of proteins has little effect on either the order parameter of the lipids in the bilayer or the lipid dynamics, as measured by relaxation times. The overall view resulting from NMR experiments is 1) that the exchange rate between boundary and free lipids is rapid, (107 sec−1), 2) that the order parameters of the bound lipid are barely affected by being adjacent to proteins, 3) that the dynamics of the acyl chain reorientations are slowed only slightly in the frequency range of 109 sec−1, and 4) that the orientation and the dynamics of the polar headgroups are similarly unaffected in any substantial manner by being adjacent to transmembrane proteins. 13C-NMR spectrum also gives information on specific lipid-protein interactions of biomembranes Recent results using non labeled optical methods such as Dual Polarisation Interferometry which measure the birefringenceAlireza Mashaghi et al. "Optical anisotropy of supported lipid structures probed by waveguide spectroscopy and its application to study of supported lipid bilayer formation kinetics" Anal. Chem.
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In the most common means for its production, cells make 5-oxo-ETE in a four step pathway that involves their stimulus-induced activation of the following pathway: a) the release of arachidonic acid (i.e. 5Z,8Z,11Z,14Z-eicosatetraenoic acid) from its storage sites in membrane phospholipids due to the activation of phospholipase A2 enzymes; b) oxygenation of this arachidonic acid by activated arachidonate 5-lipoxygenase (ALOX5) to form 5(S)-hydroperoxy-6E,8Z,11Z,14Z-eicosatetraenoic acid (5(S)-HpETE); c) reduction of this 5(S)-HpETE by ubiquitous cellular peroxidases to form 5(S)-hydroxy-6E,8Z,11Z,14Z-eicosatetraenoic acid (5(S)-HETE); and (d) the oxidation of 5(S)-HETE by a microsome-bound nicotinamide adenine dinucleotide phosphate (NADP+)-dependent dehydrogenase enzyme viz., (5-Hydroxyeicosanoid dehydrogenase or 5-HEDH) to form 5-oxo-ETE: a) Phospholipid-bound arachidonic acid → free arachidonic acid b) Free arachidonic acid + O2 → 5(S)-HpETE c) 5(S)-HpETE → 5(S)-HETE d) 5(S)-HETE + NADP+ \rightleftharpoons 5-oxo-ETE + NADPH 5-HEDH has little or no ability to metabolize the R stereoisomer of 5(S)-HETE viz., 5(R)-HETE, to 5-oxo-ETE.
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Accordingly, rodent leukocyte 12-lipoxygenase is deemed an ortholog of ALOX15 and is designated as Alox15. Human ALOX12 and ALOX15 along with rodent leukocyte-type Alox12 and Alox15 are commonly termed 12/15-lipoxygenases based on their ability to metabolize arachidonic acid to both 12(S)-HpETE and 15(S)-HpETE and to conduct this same metabolism on arachidonic acid that is esterified to membrane phospholipids; human ALOX15B makes 15(S)-HpETE but not 12(S)-HpETE and therefore is not regarded as a 12/15-lipoxygenase. Studies on the role of ALOX12 in pathophysiology using the main models for such functional studies, rats and mice, are complicated because neither species possesses a lipoxygenase that makes a predominance of 12(S)-HETE and therefore is metabolically equivalent to ALOX12. For example, the functions inferred for Alox12 in mice made deficient in Alox12 using knockout methods may not indicate a similar function for ALOX12 in humans due to differences in these two enzymes' metabolic activities. The function of ALOX12 is further clouded by human ALOX15 which metabolizes arachidonic acid primarily to 15(S)-HpETE but also makes lesser but still significant amounts of 12(S)-HpETE (see ALOX15).
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Like most polyunsaturated fatty acids and mono-hydroxyl polyunsaturated fatty acids, 13(S)-HODE is rapidly and quantitatively incorporated into phospholipids; the levels of 13(S)-HODE esterified to the sn-2 position of phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine in human psoriasis lesions are significantly lower than those in normal skin; this chain shortening pathway may be responsible for inactivating 13(S)-HODE. 13(S)-HODE is also metabolized by peroxisome- dependent β-oxidations to chain-shortened 16-carbon, 14-carbon, and 12-carbon products which are released from the cell; this chain-shortening pathway may serve to inactive and dispose of 13(S)-HODE. 13(S)-HODE is oxidized to 13-oxo-9Z,11E-octadecadienoic acid (13-oxo-HODE or 13-oxoODE) by a NAD+-dependent 13-HODE dehydrogenase, the protein for which has been partially purified from rat colon. The formation of 13-oxo-ODE may represent the first step in 13(S)-HODEs peroxisome-dependent chain shortening but 13-oxo-ODE has its own areas of biological importance: it accumulates in tissues, is bioactive, and may have clinically relevance as a marker for and potential contributor to human disease.
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