Likewise arginine, ornithine, and citrulline, which are interconvertible by the urea cycle, are considered a single group.
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Although PA and DAG are interconvertible, they do not act in the same pathways. Stimuli that activate PLD do not activate enzymes downstream of DAG and vice versa. It is possible that, though PA and DAG are interconvertible, separate pools of signalling and non-signalling lipids may be maintained. Studies have suggested that DAG signalling is mediated by polyunsaturated DAG while PLD derived PA is monounsaturated or saturated.
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Chromate salts contain the chromate anion, . Dichromate salts contain the dichromate anion, . They are oxoanions of chromium in the 6+ oxidation state and are moderately strong oxidizing agents. In an aqueous solution, chromate and dichromate ions can be interconvertible.
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Structures obtained in closed and open conformations are reversibly interconvertible by changes in the pH. A hydrogen-bonded perturbed pair of conserved aspartyl residues explains the pH dependence of this transition, and the pH regulates calcium influx in proteoliposomes. Homology models for human BI-1 provided insight into its cytoprotective activity.
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Nicotinic AChRs may exist in different interconvertible conformational states. Binding of an agonist stabilises the open and desensitised states. In normal physiological conditions, the receptor needs exactly two molecules of ACh to open. Opening of the channel allows positively charged ions to move across it; in particular, sodium enters the cell and potassium exits.
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For each additional helical twist being accommodated, the lobes will show one more rotation about their axis. As a general rule, the DNA of most organisms is negatively supercoiled. Lobal contortions of a circular DNA, such as the rotation of the figure-eight lobes above, are referred to as writhe. The above example illustrates that twist and writhe are interconvertible.
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His team demonstrated the existence of several interconvertible states for the nicotinic receptor, resting, open and desensitized, displaying different affinities for the ligands, such as the endogenous agonist acetylcholine.Weber M., David-Pfeuty M.T., Changeux J.-P. (1975). Regulation of binding properties of the nicotinic receptor protein by cholinergic ligands in membrane fragments from Torpedo marmorata. Proc. Natl. Acad. Sci. USA 72: 3443-3447.
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These two interconvertible structures have two different functions, in alpha-helix form the CTD inhibits binding of the N-terminal domain to the RNA-polymerase, whereas the beta- barrel form recruits ribosomes. RfaH is thus the first member of the transformer protein class which obviously violates the original 'one sequence - one structure - one function' suggestion that governed protein research for decades .
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A planar chiral ferrocene derivative Disubstituted ferrocenes can exist as either 1,2-, 1,3- or 1,1′- isomers, none of which are interconvertible. Ferrocenes that are asymmetrically disubstituted on one ring are chiral – for example [CpFe(EtC5H3Me)]. This planar chirality arises despite no single atom being a stereogenic centre. The substituted ferrocene shown at right (a 4-(dimethylamino)pyridine derivative) has been shown to be effective when used for the kinetic resolution of racemic secondary alcohols.
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Chandrasekhar, S. (1961). In accordance with the first law for closed systems, energy transferred solely as heat leaves one body and enters another, changing the internal energies of each. Transfer, between bodies, of energy as work is a complementary way of changing internal energies. Though it is not logically rigorous from the viewpoint of strict physical concepts, a common form of words that expresses this is to say that heat and work are interconvertible.
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For example, it was shown that addition of PLD to membranes results in the production of [32P]-labeled PA and [32P]-labeled phosphoinositides. The addition of DAGK inhibitors eliminates the production of [32P]-labeled PA but not the PLD-stimulated production of phosphoinositides. It is possible that, though PA and DAG are interconvertible, separate pools of signaling and non- signaling lipids may be maintained. Studies have suggested that DAG signaling is mediated by polyunsaturated DAG, whereas PLD-derived PA is monounsaturated or saturated.
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The larger affinity of the ligand for the R state means that the latter is preferentially stabilized by the binding. The Monod-Wyman-Changeux (MWC) model for concerted allosteric transitions went a step further by exploring cooperativity based on thermodynamics and three-dimensional conformations. It was originally formulated for oligomeric proteins with symmetrically arranged, identical subunits, each of which has one ligand binding site. According to this framework, two (or more) interconvertible conformational states of an allosteric protein coexist in a thermal equilibrium.
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Tetrafluorohydrazine, unlike hydrazine itself, can dissociate at room temperature and above to give the radical NF2•. Fluorine azide (FN3) is very explosive and thermally unstable. Dinitrogen difluoride (N2F2) exists as thermally interconvertible cis and trans isomers, and was first found as a product of the thermal decomposition of FN3. Nitrogen trichloride (NCl3) is a dense, volatile, and explosive liquid whose physical properties are similar to those of carbon tetrachloride, although one difference is that NCl3 is easily hydrolysed by water while CCl4 is not.
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He also speculated that plants might use light as a source of energy for growth (i.e. photosynthesis), based on Isaac Newton's suggestion that "gross bodies and light" might be interconvertible. quoting Opticks In Vegetable Staticks Hales also described experiments that showed that "… air freely enters plants, not only with the principal fund of nourishment by the roots, but also thro' the surface of their trunks and leaves". While Hales' work on the chemistry of air appears primitive by modern standards, its importance was acknowledged by Antoine Lavoisier, the discoverer of oxygen.
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Whatever the mechanism is, such specificity is possible. It is seen in the pig testes DAGK that is specific for polyunsaturated DAG and in two rat hepatocyte LPPs that dephosphorylate different PA species with different activities. Moreover, the stimulation of SK1 activity by PS in vitro was shown to vary greatly depending on whether dioleoyl (C18:1), distearoyl (C18:0), or 1-stearoyl, 2-oleoyl species of PS were used. Thus it seems that, though PA and DAG are interconvertible, the different species of lipids can have different biological activities; and this may enable the two lipids to maintain separate signaling pathways.
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Vitamin A-deprived rats can be kept in good general health with supplementation of retinoic acid. This reverses the growth-stunting effects of vitamin A deficiency, as well as early stages of xerophthalmia. However, such rats show infertility (in both male and females) and continued degeneration of the retina, showing that these functions require retinal or retinol, which are interconvertible but which cannot be recovered from the oxidized retinoic acid. The requirement of retinol to rescue reproduction in vitamin A deficient rats is now known to be due to a requirement for local synthesis of retinoic acid from retinol in testis and embryos.
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The distinction between strict and non-strict well orders is often ignored since they are easily interconvertible. Every well-ordered set is uniquely order isomorphic to a unique ordinal number, called the order type of the well-ordered set. The well-ordering theorem, which is equivalent to the axiom of choice, states that every set can be well ordered. If a set is well ordered (or even if it merely admits a well-founded relation), the proof technique of transfinite induction can be used to prove that a given statement is true for all elements of the set.
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The concept of two distinct symmetric states is the central postulate of the MWC model. The main idea of the model is that regulated proteins, such as many enzymes and receptors, exist in different interconvertible states in the absence of any regulator. The ratio of the different conformational states is determined by thermal equilibrium. This model, alternatively termed the MWC model, is defined by the following rules: # An allosteric protein is an oligomer of protomers that are symmetrically related (for hemoglobin, we shall assume, for the sake of algebraic simplicity, that all four subunits are functionally identical).
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If it is found that PA acts only as a DAG precursor, then one can raise the question as to why cells should produce DAG using two enzymes when they contain the PLC that could produce DAG in a single step. PA produced by PLD or by DAGK can be distinguished by the addition of [γ-32P]ATP. This will show whether the phosphate group is newly derived from the kinase activity or whether it originates from the PC. Although PA and DAG are interconvertible, they do not act in the same pathways. Stimuli that activate PLD do not activate enzymes downstream of DAG, and vice versa.
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There are four distinct types of CK subunits in the tissue of mammals, which are expressed species specifically, developmental stage specifically, and tissue specifically. Ubiquitously expressed, CKMT1A is located in the mitochondrial intermembrane space and form both homodimeric and homooctameric molecules that are readily interconvertible. Like all the other CK isoenzymes, CKMT1A catalyzes the reversible transfer of the γ-phosphate group of ATP to the guanidino group of Cr to yield ADP and PCr. According to the “transport” (“shuttle”) hypothesis for the CK system, after synthesis within the mitochondrial matrix, the γ-phosphate group of ATP is transferred by CKMT1A in the mitochondrial intermembrane space to Cr to yield ADP plus PCr.
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Polymerization occurs by a so-called "loop- sheet" mechanism, in which the RCL of one molecule sequentially inserts into the A-beta-sheet of the next molecule. This process occurs preferentially when PAI-2 is in its polymerigenic form, which is stabilized by a disulfide bond between Cys-79 (located in the CD-loop) and Cys-161. When PAI-2 is in its monomeric form, the CD-loop is vastly out-of-position for this disulfide linkage, and it must translocate a distance of 54 Å to become sufficiently close to Cys-161. Nevertheless, since the CD-loop is quite flexible, the monomeric and polymerigenic forms are fully interconvertible, and one state can be favored over the other by altering the redox environment of the protein.
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In 1717 Isaac Newton speculated that light particles and matter particles were interconvertible in "Query 30" of the Opticks, where he asks: "Are not the gross bodies and light convertible into one another, and may not bodies receive much of their activity from the particles of light which enter their composition?" In 1734 the Swedish scientist and theologian Emanuel Swedenborg in his Principia theorized that all matter is ultimately composed of dimensionless points of "pure and total motion". He described this motion as being without force, direction or speed, but having the potential for force, direction and speed everywhere within it. During the nineteenth century there were several speculative attempts to show that mass and energy were proportional in various ether theories.
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Unlike Faraday, Maxwell and others (e.g., J.J. Thomson) thought that light and electricity must propagate through an ether. In Einstein's relativity, there is no ether, yet the physical reality of force is much weaker than in the theories of Faraday.Fields of Force, William Berkson, 1974Forces and Fields, Mary B. Hesse, 1961 Historian Nancy J. Nersessian in her paper "Faraday's Field Concept" distinguishes between the ideas of Maxwell and Faraday:Faraday Rediscovered: Essays on the Life and Work of Michael Faraday, 1791-1867, David Gooding, Frank A. J. L. James, Stockton Press, 1985, , , 258 pages, page 183- > The specific features of Faraday's field concept, in its 'favourite' and > most complete form, are that force is a substance, that it is the only > substance and that all forces are interconvertible through various motions > of the lines of force.
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In fact, cultural psychologists utilized multiple measurements and resources no different from other scientific researches – observation, experiment, data analysis etc. For example, Nisbett & Cohen (1996) investigated the relation between historical cultural background and regional aggression difference in the U.S.A. In this study, researchers designed laboratory experiment to observe participants' aggression, and crime rate, demographic statistics were analyzed. The experiment results supported the culture of honor theory that the aggression is a defense mechanism which is rooted in the herding cultural origin for most the southerners. In laboratory observations, Heine and his colleagues found that Japanese students spend more time than American students on tasks that they did poorly on, and the finding presents a self-improvement motivation often seen in East Asian that failure and success is interconvertible with effort.
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Living organisms produce retinal (RAL) by irreversible oxidative cleavage of carotenoids. For example, :beta-carotene + O2 -> 2 retinal catalyzed by a beta-carotene 15,15'-monooxygenase or a beta- carotene 15,15'-dioxygenase. Just as carotenoids are the precursors of retinal, retinal is the precursor of the other forms of vitamin A. Retinal is interconvertible with retinol (ROL), the transport and storage form of vitamin A :retinal + NADPH + H+ retinol + NADP+ :retinol + NAD+ retinal + NADH + H+ catalyzed by retinol dehydrogenases (RDHs) and alcohol dehydrogenases (ADHs). Retinol is called vitamin A alcohol, or more often, simply vitamin A. Retinal can also be oxidized to retinoic acid (RA) :retinal + NAD+ \+ H2O -> retinoic acid + NADH + H+ (catalyzed by RALDH) :retinal + O2 \+ H2O -> retinoic acid + H2O2 (catalyzed by retinal oxidase) catalyzed by retinal dehydrogenases also known as retinaldehyde dehydrogenases (RALDHs) as well as retinal oxidases.
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