Thallium (I) interactions in biological fluids: a potentiometric investigation of thallium(I) complex equilibria with some sulphur-containing amino acids.
Formation constants for thallium(I) complexes of L-cysteine (CysH2), DL-penicillamine (PenH2), N-acetyl-L-cysteine (AcyH2), and N-acetyl-DL-penicillamine (ApeH2) in aqueous solution have been determined in 150 mmol dm-3 NaCl medium at 37 degrees C by potentiometric titrations using a glass electrode. Glycine has been used as a model for simple amino acids. The experimental data may be explained by the formation of the complexes T1(Cys)-, T1(Cys)H, T1(Pen)-, T1(Pen)H, T1(Acy)-, and T1(Ape)- with log formation constants 3.26, 11.28, 3.60, 12.05, 2.27, and 2.45, respectively. Analysis of the results obtained and comparison of thallium(I) complexing ability with that of dimethyl-thallium(III) seem to indicate that thallium(I) toxicity does not directly stem from its interference with the metabolism of sulphur-containing compounds.
García Bugarín
M
M
Departamento de Quimica Inorgánica, Universidad de Santiago de Compostela, Spain.
Casas
J S
JS
Sordo
J
J
Filella
M
M
D000111:Acetylcysteine; D000596:Amino Acids / Q000378:metabolism; D055598:Chemical Phenomena; D002621:Chemistry; D003545:Cysteine; D007700:Kinetics; D010396:Penicillamine / Q000031:analogs & derivatives; D011199:Potentiometry; D013793:Thallium / Q000378:metabolism
D000596:Amino Acids; C010005:N-acetylpenicillamine; D013793:Thallium; D010396:Penicillamine; D003545:Cysteine; D000111:Acetylcysteine