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-methylmercaptoacetate, 2-mercaptosuccinic acid, L-Cys, D,L-penicillamine, N-acetyl-D,L-penicillamine, glutathione, thiocholine and 4-mercapto-N-methylpiperidine were determined by potentiometric titration. For the equilibrium MeHg+ + RS .dblarw. [McHgSR]1-n, log .beta. occurred in the range 14.60(1)-17.41(1), with the lowest value obtained for the cationic complex of thiocholine, .**GRAPHIC**. Acid Kd for the ligands were reported. Formation constants for the addition of 1 and 2 equivalents of MeHg(II) to L-Cys were determined, giving log K .apprx. 4.1 for the reaction .**GRAPHIC**. + MeHg+ .dblarw. .**GRAPHIC**. occurring at low pH, and log K 8.8 for the reaction MeHgSCH2CH(NH2)CO2- + MeHg+ .dblarw. .**GRAPHIC**. occurring at higher pH.