Binding of competitive inhibitors to the different pH-dependent forms of trypsin
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Benzamidine
Dissociation constant
Optical rotatory dispersion
Complex formation
The transformation of α-d-isosaccharinic acid into α-d-isosaccharino-1,4-lactone proceeds relatively slowly. Consequently, the transformation constant, KL, has been determined kinetically in 1.0 mol·dm−3 NaClO4 and at 23 °C. A previous determination in 0.1 mol·dm−3 NaClO4 and at 23 °C has been reinterpreted. The values obtained have been coupled with other data in the literature to demonstrate that the magnitude of the transformation constant is independent of ionic strength, and its value was determined to be log KL° = 0.80 ± 0.02. Data from the literature for the dissociation of α-d-isosaccharinic acid have been re-evaluated to determine both the "intrinsic" and "composite" dissociation constants at zero ionic strength, namely, log Ka° = −4.04 ± 0.06 and log Kc° = −4.90 ± 0.07, respectively. The present data permit a much more thorough understanding of the aqueous chemistry of α-d-isosaccharinic acid to be ascertained than has previously been possible.
Dissociation constant
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Abstract The effects of ionic strength and pH on adsorption of lysozyme to three strong cation exchangers have been studied. Adsorption equilibrium data obtained using the batch techniques corresponded well to the Langmuir isotherm. Ionic strength had a considerable influence on the isotherms. In all cases, the maximum binding capacity of the three exchangers decreased while the apparent dissociation constant increased with increasing ionic strength. The maximum binding capacity also decreased while the apparent dissociation constant was not significantly affected by an increase in pH. It was found that the three exchangers exhibited different levels of binding capacity under identical solution conditions. This was shown to be caused by variation in the arrangement and distribution of charged groups. However, the ion‐exchange matrix had little effect on the apparent dissociation constant.
Dissociation constant
Langmuir adsorption model
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Dissociation constant
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Benzamidine
Dissociation constant
Benzylamine
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To study the metal-ligand equilibrium in aqueous solution, the well known Irving-Rossotti titration method was used. The temperature selected is 25 ± 0.5°C at ionic strength 1M (NaClO4) which was maintained constant throughout the complexation.
Complex formation
Constant (computer programming)
Equilibrium solution
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Dissociation constant
Acid dissociation constant
Constant (computer programming)
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Abstract Affinity chromatographically purified C1̄ was demonstrated to be inhibitable by a variety of benzamidine and pyridinium fluorosulfonyl-substituted compounds. Four of the compounds tested afforded greater than 50% inhibition at concentrations between 10-6 and 10-5 M. The data indicated that inhibition was greatest with those compounds which contained a substituted benzamidine and sulfonyl-fluoride group. The site of action was the esterase activity associated with the C1.
Benzamidine
Esterase
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Thrombin is a serine protease responsible for blood coagulation. Since thrombin inhibitors appear to be effective in the treatment and prevention of thrombotic and embolic disorders, considerable attention has been focused on the structure and interactions of this enzyme. In this work, to evaluate the relative free energies of hydration and binding to thrombin for some benzamidine derivatives, we used the finite difference thermodynamic integration (FDTI) algorithm within the Discover program of MSI. By this method, two possible orders of hydration for the candidates were obtained: p-amidinophenylpyruvate > p-(2-oxo-1-propyl)benzamidine > p-methylbenzamidine > p-ethylbenzamidine > p-(1-propyl)benzamidine > benzamidine and p-amidinophenylpyruvate > p-(2-oxo-1-propyl)benzamidine > p-methylbenzamidine > p-ethylbenzamidine > benzamidine > p-(1-propyl)benzamidine. We also obtained the following order for thrombin binding: p-(2-oxo-1-propyl)benzamidine > p-ethylbenzamidine > p-(1-propyl)benzamidine > p-methylbenzamidine > benzamidine > p-amidinophenylpyruvate.
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The dissociation constant for hirudin was determined by varying the concentration of hirudin in the presence of a fixed concentration of thrombin and tripeptidyl p-nitroanilide substrate. The estimate of the dissociation constant determined in this manner displayed a dependence on the concentration of substrate which suggested the existence of two binding sites at which the substrate was able to compete with hirudin. A high-affinity site could be correlated with the binding of the substrate at the active site, and the other site had an affinity for the substrate that was 2 orders of magnitude lower. Extrapolation to zero substrate concentration yielded a value of 20 fM for the dissociation constant of hirudin at an ionic strength of 0.125. The dissociation constant for hirudin was markedly dependent on the ionic strength of the assay; it increased 20-fold when the ionic strength was increased from 0.1 to 0.4. This increase in dissociation constant was accompanied by a decrease in the rate with which hirudin associated with thrombin. This rate could be measured with a conventional recording spectrophotometer at higher ionic strength and was found to be independent of the binding of substrate at the active site.
Hirudin
Dissociation constant
Michaelis–Menten kinetics
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Derivatives of benzamidine inhibit competitively the activity of the serine proteinases trypsin, plasmin, thrombin, and of the clotting factor Xa. The inhibitor activities (Ki-values) of various benzamidine derivatives against the several enzymes were compared. Besides parallels, deviations in the corresponding structure-activity relationships were found. From these results it is concluded that the similar enzymes exhibit certain differences in the structure of the primary and secondary binding sites.
Benzamidine
Reversion
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