Autoinhibition

Electron delocalization in a conjugated system is generally accompanied by a decrease in radical reactivity. When the extent of conjugation increases with each monomer adition, the active centre soon loses its ability to attack the 

The above-mentioned reactions have not been sufficiently studied so far, although they are of considerable interest, as they could yield thermostable polymers or organic semiconductors. With radical initiators, only oligomers are always formed, with a large content of cycles. Most authors assume that the reluctance of acetylenes to yield long chains is connected with the attenuation of centre reactivity, i.e. with inter- and intramolecular delocalization of the unpaired electron in the growing macroradical [79]. 

Criticisms have been voiced [80], Nevertheless, termination of polypheny-lacetylene growth is of the first order, as proved by Amdur et al. Most probably it is also connected with intramolecular electron transfer or structural change, leading to a less active centre [81]. 

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Yamada K M and Kennedy D W 1978 Dualistie nature of adhesive protein funetion fibroneetin and its biologieally aetive peptide fragments ean autoinhibit fibroneetin funetion J. Cell Biol. 99 29-36... 

Gandini and Rieumont26,119 have carried out an extensive examination of the polymerizability of several vinyl esters of furan carboxylic acids and of the causes of the autoinhibition which most of them display with free-radical initiation. The compounds studied were the vinyl esters of 2-furoic, 2-furylacetic, 2-furylpropionic, 2-furylacrylic and sorbic acid. All these derivatives, showed the same strong indifference towards radical polymerization. Only when treated with large doses (10—30%) of initiator did they give small yields of oligomers. The structure of all these products was carefully studied by spectroscopic and other techniques. Invariably, it was... 

Many of the neuroleptics are a-adrenoceptor antagonists. Some, like chlorpromazine, block d postsynaptic receptors while clozapine (and risperidone) are as potent at 2 as D2 receptors. There is no evidence that either of these actions could influence striatal or mesolimbic function but NA is considered important for function of the prefrontal cortex and any increase in its release, achieved by blocking a2-mediated autoinhibition, might contribute to a reduction in negative symptoms and provide a further plus for clozapine (see Nutt et al. 1997). Centrally, however, most a2-receptors are found postsynaptically and their function, and the effect of blocking them, is uncertain. 

The presence of I and smaller amounts of other OFAs in algae (Table III) is interesting in view of autoinhibition of algae cultures (7, 20, 21). Autoinhibition occurs as cultures begin to age at... 

Wybenga-Groot, L. E. et al., Structural basis for autoinhibition of the EphB2 receptor tyrosine kinase by the unphosphorylated juxtamembrane region, Cell, 106, 745-757, 2001. 

Arrang, J. M., Garbarg, M. Schwartz, J. C. (1987b). Autoinhibition of histamine synthesis mediated by presynaptic H3-receptors. Neuroscience 23, 149-57. 

On the other hand, carbonyl quenching by polyenyl radicals in PVC has been invoked in order to account for autoinhibition during photooxidative degradation (52). Some workers have mentioned the possibility of singlet oxygen formation in PVC via the quenching of excited polyenes (25,29) or cyclohexadienes (53). 

The autoinhibiting effect which was apparent in the later stages, particularly for thicker films, was attributed to the formation of charge transfer complexes between HC1 and polyenes. These complexes were assumed to be photochemically inert as far as further dehydrochlorination of the polymer was concerned but may be involved in the reverse process of re-addition of HC1 to the polyenes. The balance between the two effects depends on the ease of diffusion of HC1 out of the film. 

The key in activation of Src family kinases is the disruption of intramolecular interactions and relief of autoinhibition. In addition to dephosphorylation of Y527 by PTPs, the SH2-phosphoY527 bond can be disrupted by competition with a high affinity phosphotyrosine ligand. 

Kinetic studies of the acetylation of several arylethers were carried out over HBEA zeolites. The main conclusion is that the rate and stability of the reactions are determined by the competition between reactant(s) and product(s) molecules for adsorption within the zeolite micropores. This competition shows that the autoinhibition of arene acetylation, that is, the inhibition by the acetylated products, and also by the very polar acetic acid product is generally observed. This effect is much more pronounced with hydrophobic substrates such as methyl and fluoro aromatics than with hydrophilic substrates because of the larger difference in polarities between substrate and product molecules. 

J. Lewis, Autoinhibition with transcriptional delay A simple mechanism for the zebrafish somitogenesis oscillator. Curr. Biol. 13, 1398-1408 (2003). 

In addition to the physiological process of autoinhibition, another mechanism of presynaptic inhibition has been identified in the peripheral nervous system, although its precise relevance to the brain is unclear. In the dorsal horn of the spinal cord, for example, the axon terminal of a local neuron makes axo-axonal contact with a primary afferent excitatory input, which leads to a reduction in the neurotransmitter released. This is due to the local neuron partly depolarizing the nerve terminal, so that when the axon potential arrives, the change induced is diminished, thereby leading to a smaller quantity of transmitter being released. In the brain, it is possible that GABA can cause presynaptic inhibition in this way. 

Action. cAMP is an allosteric effector of protein kinase A (PK-A, [3]). in the inactive state, PK-A is a heterotetramer (C2R2), the catalytic subunits of which (C) are blocked by regulatory units (R autoinhibition). When cAMP binds to the regulatory units, the C units separate from the R units and become enzymatically active. Active PK-A phosphorylates serine and threonine residues of more than 100 different proteins, enzymes, and transcription factors, in addition to cAMP, cCMP also acts as a second messenger, it is involved in sight (see p. 358) and in the signal transduction of NO (see p. 388). 

Upon binding calcium ions, the small acidic protein known as calmodulin can activate enzymes by binding to a wide variety of proteins containing cahnodulin-binding domains. Such proteins include cAMP phosphodiesterase, calmodulin-dependent nitric oxide synthase, calmodulin kinases, the plasma membrane calcium pump, calcineurin, and calmodulin-dependent inositol-(l,4,5)-trisphosphate 3-kinase. See also Activation Autoinhibition... 

BIFURCATION THEORY PRION PLAQUE FORMATION Autocatalytic processes during evolution, HYPERCYCLE AUTOINHIBITION ACTIVATION... 

Calmodulin-binding domain of Ca + pump, AUTOINHIBITION CALOMEL ELECTRODE CALORIMETRY... 

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