Chelation of Lanthanum (La3+) by Various Thiols - an in vitro Study

In the present study the interaction of various thiols (L-glutathione, L-cysteine, N-acetyl cysteine and D-penicillamine) with LaCl₃ was studied in vitro by modified Ellman’s method. Experiments carried out at various concentrations inferred gradual decrease in thiol concentration with the increase in La³⁺ concentration in aqueous solutions. Maximum interac-tion between thiols and La³⁺ was observed at pH 7.5 and 35°C as indicated by the lowest values of residual thiol con-centration. The order of reactivity was DPA>GSH>NAC>Cys, where reactivity increased with increasing pKa of their thiol group. The possible products of reaction are proposed to be La(RS)₃ complex or oxidized form with disulfide bond (RSSR).