Methylmercury(II) sulfhydryl interactions. Potentiometric determination of the formation constants for complexation of methylmercury(II) by sulfhydryl containing amino acids and related molecules, including glutathione

Abstract

Formation constants for the interaction of methylmercury(II) with 2-mercaptoethanol, mercaptoacetic acid, O-methyl-mercaptoacetate, 2-mercaptosuccinic acid, L-cysteine, D,L-penicillamine, N-acetyl-D,L-penicillamine, glutathione, thiocholine, and 4-mercapto-N-methylpiperidine have been determined by potentiometric titration. For the equilibrium [Formula: see text], log β occurs in the range 14.60(1)–17.14(1), with the lowest value obtained for the cationic complex of thiocholine, [Formula: see text]. Acid dissociation constants for the ligands are reported. Formation constants for the addition of both one and two equivalents of MeHg(II) to L-cysteine have been determined, giving log K ca. 4.1 for the reaction[Formula: see text]occurring at low pH, and log K 8.8 for the reaction[Formula: see text]occurring at higher pH.

Density Functional Theory Calculation of pKa’s of Thiols in Aqueous Solution Using Explicit Water Molecules and the Polarizable Continuum Model

“…The experimental pK a 's for this set of organic thiols are listed in Table 1 and range from 4 to 12 pK a units. [65][66][67][68][69][70][71][72][73][74][75][76] The test calculations in Figure 1 indicate that there is a large error in the calculation of the pK a 's for simple thiols. In previous studies on nucleobases, we found that the methods that performed well for pK a 's of cation-neutral pairs often performed poorly for pK a 's of neutral-anion pairs.…”

Nuclear magnetic resonance and potentiometric studies of the complexation of methylmercury(II) by dithiols

“…[2] and using these values for k3 and Kdp yielded a value of log kw = 17.16 f 0.05. The formation constants calculated for the deprotonated 1 : I complex and the 2: 1 complex (eqs.…”

“…2. Equilibrium constants were obtained from titration data using a version of MINIQUAD (12) by procedures described previously (2).…”

“…Methylmercury, CH3Hg(II), forms very stable complexes with monothiols (1,2), with the result that CH3Hg(II) is thought to be essentially all thiol-bound in biological systems. For example, in human erythrocytes, CH3Hg(II) is bound almost entirely to glutathione (ca.…”

Influence of Dielectric Constant on Protonation Equilibria of Mercaptosuccinic Acid, L-Dopa and 1, 10-Phenanthroline in Aqueous Solutions of Dimethylformamide.

“…Hence, the logarithm of stepwise protonation constants (log K) should vary linearly as a function of the reciprocal of the dielectric constant of the medium. It is observed that in DMF media the log K values of MSA, dopa and phen increase linearly as a content of organic containing pure water as a solvent [28][29][30][31] but small differences are possibly due to the different experimental procedures ,temperature and different background electrolytes used. In this study the linear variation of log K values as a function of 1/D (figure 8) in mixtures shows that the dominance of electrostatic interactions.…”