Rate of inhibition

Ans. (a) Inhibition of rate (b) shorter induction time as molybdenum is already in the 6+ oxidation state. 

In none of our studies of ligand binding by peroxidases or hemin have we obtained any evidence of inhibition of rate at high hgand concentration which would indicate either a dissociative or ion-pair mechanism (28,29). This lack of evidence does not exclude such mechanisms, however. From a comparison of imidazole binding rate with solvent exchange rate by hemin in an ethanol—water solvent, our results favored an ion-pair mechanism (30, 31). 

Figure 5.10. Variation of order of reaction with increasing pressure of carbon dioxide or steam to illustrate inhibition of rates of reaction (g m s ).

The volume of micropores and their size distributions in activated carbons, are a function of (a) the activation equipment (b) bum-off (c) the starting carbonaceous precursor (d) the activating gas (e) rate of gasification (a function of temperature) (f) rate of diffusion of activating gas(es) into and product gas(es) out of the carbon (g) extent of product inhibition of rate (h) amount and nature of inorganic impurities in char and (i) amounts of oxygen surface complexes present. 

The catalysis by alkali-metal ions with the selectivity order Li+ > Na+ > K+ > Cs+ is also found in the ethanolysis of 4-nitrophenyl diphenylphosphinate (24). " But, in the ethanolysis of 4-nitrophenyl benzenesulfonate (25), Li+ brought about an inhibition of rate, and the catalytic order of the other alkali metals was K+ > Cs+ > Na+." These observations have been explained in terms of calculated free energy difference between the free energy of TS and free energy of metal ion stabilization of ethoxide ion."° Nucleophilic demethylation of tri-CHj (26) and di-CHj 2-pyridylmethyl (27) phosphates by iodide is catalyzed by alkali-metal ions and the effect increasing in the order K+ < Na+ < Li+."3 The catalytic effect is more pronounced for 27. The crown ethers reduce, but do not eliminate the catalysis, indicating strong interactions between the reaction TS and the metal ions. Similar effects of crown ethers are observed in the ethanolysis of 23 in the presence of alkali metals." ... 

Transgenic soybean plants expressing the CTP-CP4 EPSPS display commercial levels of Roundup tolerance. These results vaUdate the importance of substrate kinetics of EPSPS in order to maintain adequate rates of aromatic biosynthesis. Furthermore, the fact that glyphosate tolerance can be obtained by expression of a glyphosate-tolerant EPSPS illustrates that the herbicidal mode of action of glyphosate is related solely to inhibition of the EPSPS reaction. 

Not only is TCDO a potent therapeutic agent in acute radiation syndrome, but treatment using TCDO from days 4—11 after TBI increases the survival rate in rats for up to one year, protects against the development of late GI ulcers, and also reduces the development of y-ray-induced leukemias and malignant epitheHal tumors, but not sarcomas (202). The anticarcinogenic effect of TCDO maybe related to the inhibition of PGs, which promote carcinogenesis, or to immunostimulation, which may result in a more effective elimination of malignant cells. 

When administered intraperitoneaHy, sulfolane is excreted both unchanged and as 3-hydroxysulfolane [13031 -76-0] (24). Sulfolane injected intraperitoneaHy in mice and rats at 200—800 mg/kg at ambient temperatures of 15 and 25°C caused a dose-related inhibition of the metaboHc rate and hypoactivity, accompanied by hypothermia 60 min after injection. Despite their hypothermic condition these animals did not select a warm ambient temperature. Because sulfolane toxicity appears to be greater upon increased tissue temperature, the behavior of these animals seeking lower environmental temperature appears to enhance their chance of survival (25—28). 

The Class I agents decrease excitability, slow conduction velocity, inhibit diastoHc depolarization (decrease automaticity), and prolong the refractory period of cardiac tissues (1,2). These agents have anticholinergic effects that may contribute to the observed electrophysiologic effects. Heart rates may become faster by increasing phase 4 diastoHc depolarization in SA and AV nodal cells. This results from inhibition of the action of vagaHy released acetylcholine [S1-84-3] which, allows sympathetically released norepinephrine [51-41-2] (NE) to act on these stmctures (1,2). 

Decreased production of yolk protein resulting from inhibition of either ovarian or liver function presents the fish with a similar choice to that resulting from decreased food availability. It can produce the same number of smaller eggs, or a smaller number of eggs of normal size, but the mechanism by which that choice is made is unclear. Since the decreased nutrient content of small eggs will result in smaller larvae with a decreased survival rate, the net result in both cases may be a... 

The effect of conversion is mostly an economic indicator. Additionally, a strong slowdown can indicate a reversible reaction. If this possibility is excluded by thermodynamic estimates, a strong inhibition of the rate is... 

Figure 6.3.2 shows the feed-forward design, in which acrolein and water were included, since previous studies had indicated some inhibition of the catalytic rates by these two substances. Inert gas pressure was kept as a variable to check for pore diffusion limitations. Since no large diffusional limitation was shown, the inert gas pressure was dropped as an independent variable in the second study of feed-back design, and replaced by total pressure. For smaller difftisional effects later tests were recommended, due to the extreme urgency of this project. 

Secondary steric effects of nitro groups are more easily detected by comparing the reactivities with those of aza derivatives. For example, in structure 20 the rate depression on passing from methyl to -butyl is only 2.5-fold and can be attributed to an inductive effect, whereas in structure 21 a similar change involves the factor 16, which can be attributed in part to steric inhibition of resonance (S.I.R.) of thep-N02 group (reaction with piperidine). 

When a hydrogen atom is peri to an azine-nitrogen, there is no steric inhibition of resonance activation as there is in 1-nitronaph-thalene (4-methoxy-dechlorination of its 4-chloro derivative seems to be thereby decelerated only 2-fold in rate). Steric hindrance of nucleophihc substitution by the co-planar peri hydrogen is sometimes... 

Complete inhibition of corrosion in waters containing high concentrations of chloride is difficult, if not impossible to achieve economically. Despite this, many such systems make use of inhibitors to give marked reductions in corrosion rates. 

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