Abstract

A Comparative Investigation of Interaction Between Metal Ions with L-Cysteine and L-Methionine Related Compounds in Aqueous Solution

Author(s): Sajadi SAA

The acidity and stability constants ofM-Met (M: M2+; Met: L-methionine) complexes, determined by potentiometric pH titrations, were used to make a comparative investigation with L-cysteine (Cys). The stability constants of the 1:1 complexes formed between M2+ and Met, were determined by potentiometric pH titration in aqueous solution (I = 0.1M, NaNO3, 25C). The order of the stability constants was reported. It is shown that regarding toMion – binding properties vital differences on complex bilding were considered. It is demonstrated, that inM-Met complexes,Mion is coordinated to the carboxyl group, M ion is also able to bild macrochelate over amine group. The upmentioned results demonstrate that for M-Met complex the stability constants is also largly determined by the affinity of Cu2+ for amino group but in opposite to Met, some metal ions such as Co2+, Cu2+, and Zn2+ build with Cys macrochelate over sulfur group. It is shown that this additional interaction with amino groups and sulfur group can influence the character of some amino acid compleses in biological systems.