Function Of Inhibitor Concentration Research Articles

Characterization of positive resist development

The development of positive photoresist is assumed to be a surface limited reaction whose development rate is determined by the local inhibitor concentration M, as defined by Dill et al. This paper describes a technique for determining development rate as a function of inhibitor concentration and demonstrates the usefulness of the technique for quality control. Resist development parameters for the simulation of line edge profiles in resist are presented.

A kinetic analysis of the hydrolysis of synthetic arginine substrates by arginine esterases from the venom of the gabooon adder, Bitis gabonica.

The kinetics of arginine esterases E-I, E-II and E-III from the venom of Bitis gabonica were investigated. With N alpha-benzoyl-L-arginine ethyl ester as substrate linear competitive inhibition versus L-arginine was observed while ethanol gave rise to S-parabolic I-linear noncompetitive inhibition. Hydrolysis of N alpha-benzoyl-L-arginine-p-nitroanilide was noncompetitively inhibited by p-nitroaniline. Both slopes and intercepts of double reciprocal plots were a linear function of inhibitor concentration. Ethanol gave complex inhibition kinetics which could be interpreted in terms of mixed dead-end and alternate product inhibition (S-parabolic I-hyperbolic noncompetitive inhibition). These results imply an ordered uni-bi as the minimal kinetic mechanism wherein ethanol (or amine when amide is used as substrate) is released first from the enzyme surface, followed by the liberation of arginine. The enzymes are inactivated by phenylmethane sulfonyl fluoride which suggests the presence of an essential serine in the active sites of the enzymes. The enzymes may therefore be classified in the group of serine proteases.

Enzyme electrode for inhibitors determination: urease-fluoride system

An enzyme electrode is constructed and optimized for inhibitor determination. The urease electrode inhibited by fluoride ions is chosen as an example to illustrate the procedure. The enzyme is chemically bound with glutaraldehyde to a silicone membrane which is a part of the CO2 gas electrode. The inhibition reversibility is tested and various parameters related to the enzyme cross-linking technique are studied separately. The theoretical and experimental behaviors of the enzyme electrode as a function of inhibitor concentration are compared by analyzing the steady-state substrate and product concentration profiles inside the active layer. This study defines the optimum operating conditions for the use of an enzyme electrode.

Nature of inhibition of rat testicular alkaline phosphatase by isatin.

Isatin has been found to inhibit rat testicular alkaline phosphatase (EC 3.1.3.1). That the inhibition is non-competitive as well as non-allosteric is evident from a) the hyperbolic curve relating inhibition as a function of inhibitor concentration; b) the small change in enthalpy, free energy and entropy; c) the number of isatin molecules associating with 1 molecule of the enzyme (n=1.29); and, d) the decrease in the values of both Km and Vmax in the presence of isatin.

Binding of competitive inhibitors to the different pH-dependent forms of trypsin

Some of the rotatory, spectral, ionic and catalytic properties of trypsin (EC 3.4.4.4) have been studied, in the pH range from 1.5 to 12.5, in the presence and absence of synthetic competitive inhibitors. In the alkaline and acidic pH ranges where trypsin is reversibly denatured, the formation of the trypsin-inhibitor complex protects the enzyme against transconformation; at neutral pH, where trypsin is in the native form, the complex formation sometimes induces a change in the enzyme structure. In the alkaline pH range (a) the rotatory dispersion curve of the complex is pH independent; (b) the formation of the complex induces a decrease of the enzyme absorbance; (c) the formation of the complex produces a proton uptake by the enzyme; (d) the affinity of inhibitors decreases when the pH increases. All these results can be related to the ionization of an enzyme group having an apparent pK of about 10. In the acidic pH range (a) the rotatory power of the complex is pH independent, and (b) the complex formation produces a proton release by the enzyme. The changes in the ionic and rotatory properties of trypsin as a function of inhibitor concentration have allowed the evaluation of the dissociation constant of the benzamidine-trypsin complex between pH 4.5 and 1.5. A scheme for the interaction between the inhibitor and the different pH dependent forms of trypsin is proposed: it accounts for the pH dependence of the complex dissociation constant and also for the dependence of the number of protons released by the enzyme. The lowering of the inhibitor affinity in the acidic pH range is due to the protonation of two enzyme groups, one having an apparent p K of 3.7, the other a true pK of 4.5. At neutral pH, the enzyme-inhibitor complex formation may induce a change in both the enzyme and the inhibitor structure; formation of the trypsin-proflavin complex, for instance, makes the inhibitor optically active.

Coverage of iron surface by organic compounds and anions in acid solutions

The electrical double layer capacities at the interface between iron and acid solutions containing organic inhibitors and halide ions were measured as a function of inhibitor concentrations. The degree of surface coverage as calculated from the change in capacity due to adsorption of inhibitors was compared to inhibitor efficiency. These showed a linear relationship which might be used as a means for evaluation of inhibitors. Peaks in coverage-concentration or inhibitor-efficiency-concentration curves are interpreted in terms of a change of mechanism from adsorption to film-forming inhibition. Synergism of amines and halide ions is discussed from a viewpoint of surface charge. A model of co-adsorption using halide ions and organic cations suitably interprets the phenomenon.

The esters of 4‐hydroxybenzoic acid and related compounds. IV. The bacteriostatic action of n‐alkyl 4‐hydroxybenzoates

AbstractDetailed growth curves based on progressive turbidity readings have been used to study the inhibition of Aerobacter aerogenes Type I, by a series of alkyl 4‐hydroxybentoates. Results in the lag phase are irregular, but it is apparent that the elongation of this phase becomes very marked at the higher concentrations of the inhibitor and that complete inhibition of growth occurs at a concentration that extends lag indefinitely rather than at one which reduces the growth rate to zero. Inhibition in the logarithmic phase, plotted as a function of inhibitor concentration, gives curves convex to the abscissa that contrast with experience of fungi, where characteristic concave adsorption forms have been obtained. However, the convexity of the present series of curves is likely to be a reflection of secondary effects associated with this method of determining bacterial inhibition, particularly in that there is a loss of viability in cells exposed to the higher concentrations. Determinations based on stationary populations arc convenient and give good agreement between experiments, but are not necessarily related in any simple fashion to growth rate inhibition.Although the order of increasing activity with increasing chain length of the esters is similar that found for fungi the activity of the methyl ester is less against Aerobacter aerogenes so that solubility difficulties soon prevent the attainment of a reasonable level of inhibition.Growth curve methods that use a relatively small inoculum with consequent lag phase of variable length do not appear well suited for a direct study of growth rate inhibition.Growth curve method that use a relatively small inoculum with consequent lag phase of variable length do not appear well suited for a direct study of growth rate inhibition. A simple method better suited to this purpose is being developed.