Substance inhibitor

Inhibitor An agent dial prevents die normal action of an enzyme without destroying it (e.g., a substance (inhibitor) B causes die slowdown of die enzyme-substrate reaction of A —> R). 

Hemmungskdrper, m. inhibiting or restraining substance, inhibitor, decelerator,... 

The region of implementation of a particular mechanism of inhibited oxidation in the coordinates T—[RH]—[InH] is a combination of oxidized substances, inhibitors, and reaction conditions for which this mechanism is appropriate. 

The following equipment can be used to investigate the thermal stability, the operating temperature to avoid hazardous decomposition, the autocata-lytic decomposition of a substance, inhibitor depletion in the system, and rates of pressure rise ... 

Let us consider a unimolecular reaction on the surface. Let that at any time, surface covered by reactant (A) is 0 and surface covered by substance (inhibitor) is Gj. Then... 

Inhibition — is a decrease in the reaction rate caused by a substance (- inhibitor) affecting the concentration of a reactant, catalyst, or reaction intermediate. For example, molecular oxygen and p-benzoquinone can react as inhibitors in many reactions involving radicals as intermediates by virtue of their ability to act as scavengers toward these radicals. If the rate of a reaction in the absence of inhibitor is Vq and that in the presence of a certain amount of inhibitor is v, the degree of inhibition, i, is given by... 

Oxidations that are carried out with atmospheric oxygen usually lead to peroxy compounds. The attack by oxygen is generally highly selective and is strongly influenced by activating groups. Autoxidations are very sensitive to added substances (inhibitors or initiators). 

Decrease in rate occ2t ioned by a substance (inhibitor, poison) which may be produced by the reacdon itself or may be a foreign substance. 

The formation of polymer can be followed directly by isolation of the polymer as it is produced. This method has the advantage that the physical and chemical structure of the polymer can be studied as a function of conversion. In this method, the polymerization is terminated by adding suitable substances (inhibitors in free radical polymerization) or by quenching the reaction by cooling rapidly. The monomer and/or solvent can be distilled from the polymer, although often not all the monomer can be removed when the polymerizate viscosity is high. In addition, neither the initiator nor the catalyst is removed. A distillation must in any case be carried out at very low temperatures, since otherwise the polymer may be degraded or the polymerization may continue. 

Inhibition The decrease in the rate of reaction brought about by the addition of a substance (inhibitor), by virtue of its effect on the concentration of a reactant, catalyst, or reaction intermediate. 

The relationship between the efficiency of the substances inhibitor action and the nature of the halogen and the effect of small concentration of additives confirm that the inhibitor mechanism of halogens and their derivatives on the ignition and combustion of model systems has a chemical origin. It was discovered that halogens and their compounds do not affect the oxidation of carbon to carbon dioxide [63]. At the same time, they essentially inhibit the oxidation of CO to CO2 [64] and the formation of formaldehyde during combustion of methane. 

The cases when the initial substances (inhibitors or non-inhibitors) interact to form labile or stable products, inhibitors, are rather abundant. Very often one of these substances is an inhibitor, so that this interaction results in the more efficient retardation, i.e., synergetic effect. 

When a substance-inhibitor InH, which rapidly reacts with the hydrogen atom, is... 

This compound is the first exampie of a naturai substance inhibitor of isoprenyicysteine carboxyi methyitransferase. its name necaiis that two bromotyrosyi units are separated by a spermine. 

Enzyme action is frequently accelerated or retarded by the presence of other substances both organic and inorganic. Such substances have been divided into three categories (a) co-enzymes, without which certain enzymes are unable to function (i) activators, and (c) inhibitors. 

We conclude this section by noting an extreme case of chain transfer, a reaction which produces radicals of such low reactivity that polymerization is effectively suppressed. Reagents that accomplish this are added to commercial monomers to prevent their premature polymerization during storage. These substances are called either retarders or inhibitors, depending on the degree of protection they afford. Such chemicals must be removed from monomers prior to use, and failure to achieve complete purification can considerably affect the polymerization reaction. 

Inhibitors and retarders differ in the extent to which they interfere with polymerization, and not in their essential activity. An inhibitor is defined as a substance which blocks polymerization completely until it is either removed or consumed. Thus failure to totally eliminate an inhibitor from purified monomer will result in an induction period in which the inhibitor is first converted to an inert form before polymerization can begin. A retarder is less efficient and merely slows down the polymerization process by competing for radicals. 

Since feeds contain other substances than those required by the animals of interest, studies have also been conducted on antinutritional factors in feedstuffs and on the use of additives. Certain feed ingredients contain chemicals that retard growth or may actually be toxic. Examples are gossypol in cottonseed meal and trypsin inhibitor in soybean meal. Restriction on the amount of the feedstuffs used is one way to avoid problems. In some cases, as is tme of trypsin inhibitor, proper processing can destroy the antinutritional factor. In this case, heating of soybean meal is effective. 

The specific surface, a, is also relatively insensitive to the duid dynamics, especially in low viscosity broths. On the other hand, it is quite sensitive to the composition of the duid, especially to the presence of substances which inhibit coalescence. In the presence of coalescence inhibitors, the Sauter mean bubble size, is significantly smaller (24), and, especially in stirred bioreactors, bubbles very easily circulate with the broth. This leads to a large hold-up, ie, increased volume fraction of gas phase, 8. Sp, and a are all related... 

Neurokinin effects are terrninated by proteolysis. In vitro acetylcholinesterase (ACE) and enkephalinase can hydrolyze substance P. However, there appears to be no clear evidence that either acetylcholinesterase or ACE limit the actions of released substance P. Enkephalinase inhibitors, eg, thiorphan, can augment substance P release or action in some systems but the distribution of enkephalinase in the brain does not precisely mirror that of substance P. There appears to be a substance P-selective enzyme in brain and spinal cord. 

Other Uses. Other appHcations for sodium nitrite include the syntheses of saccharin [81-07-2] (see Sweeteners), synthetic caffeine [58-08-2] (22), fluoroaromatics (23), and other pharmaceuticals (qv), pesticides (qv), and organic substances as an inhibitor of polymerization (24) in the production of foam blowing agents (25) in removing H2S from natural gas (26) in textile dyeing (see Textiles) as an analytical reagent and as an antidote for cyanide poisoning (see Cyanides). 

Monoamine Oxidase Inhibitors. MAOIs inactivate the enzyme MAO, which is responsible for the oxidative deamination of a variety of endogenous and exogenous substances. Among the endogenous substances are the neurotransmitters, norepinephrine, dopamine, and serotonin. The prototype MAOI is iproniazid [54-92-2] (25), originally tested as an antitubercular dmg and a close chemical relative of the effective antitubercular, isoniazid [54-85-3] (26). Tubercular patients exhibited mood elevation, although no reHef of their tuberculosis, following chronic administration of iproniazid. In... 

Corrosion Inhibitors. A corrosion inhibitor is any substance that effectively decreases the corrosion rate when added to an environment. An inhibitor can be identified most accurately in relation to its function removal of the corrosive substance, passivation, precipitation, or adsorption. 

Corrosion inhibitors are substances which slow down or prevent corrosion when added to an environment in which a metal usually corrodes. Corrosion inhibitors are usually added to a system in small amounts either continuously or intermittently. The effectiveness of corrosion inhibitors is partiy dependent on the metals or alloys to be protected as well as the severity of the environment. For example, the main factors which must be considered before apphcation of a corrosion inhibitor to an aqueous system are the compatibility of the inhibitor and the metal(s), the salt concentration, the pH, the dissolved oxygen concentration, and the concentration of interfering species such as chlorides or metal cations. In addition, many inhibitors, most notably chromates, are toxic and environmental regulations limit use. Attention is now being given to the development of more environmentally compatible inhibitors (37). 

Inhibitors The use of various substances or inhibitors as additives to corrosive environments to decrease corrosion of metals in the environment is an important means of combating corrosion. This is generally most attractive in closed or recirculating systems in which the annual cost of inhibitor is low. However, it has also proved to be economicaUv attrac tive for many once-through systems, such as those encountered in petroleum-processing operations. Inhibitors are effective as the result of their controlling influence on the cathode- or anode-area reactions. 

Chemicals may be encountered as reactants, solvents, catalysts, inhibitors, as starting materials, finished products, by-products, contaminants, or off-specification products. They may vary from pure, single substances to complex proprietary formulations. 

Monitor stock, e.g. temperature, pressure, reaction, inhibitor content, degradation of substance, deterioration of packaging or containers/corrosion, leakages, condition of label, expiry date, undesirable by-products (e.g. peroxides in ethers) Spillage control bund, spray, blanket, containment. Drain to collection pit Decontamination and first-aid provisions, e.g. neutralize/destroy, fire-fighting Contain/vent pressure generated to a safe area... 

The catalytic action is specific and may be affected by the presence of other substances both as inhibitors and as coenzymes. Most enzymes are named in terms of the reactions they catalyze (see Chapter 1). There are three major types of enzyme reactions, namely ... 

Protease inhibitor (Section 28.13) A substance that interferes with enzyme-catalyzed hydrolysis of peptide bonds. 

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