A comparative investigation of interaction between metal ions with L-methionene and related compounds such as alanine, leucine, valine, and glycine in aqueous solution

Abstract

The acidity and stability constants of M-L (M: M2+; L: Met, L-methionine) complexes, determined by poten-tiometric pH titrations, were used to make a com-parative investigation. The stability constants of the 1:1 complexes formed between M2+ and L–, were de-termined by potentiometric pH titration in aqueous solution (I = 0.1 M, NaNO3, 25°C). The order of the stability constants was reported. It is shown that re-garding to M ion – binding properties, vital differ-ences on complex bilding were considered. It is dem-onstrated that in M-L complexes, M ion is coordi-nated to the carboxyl group, is also able to bild mac-rochelate over amine group. The aforementioned re-sults demonstrate that for M (Met) complex, the sta-bility constants are also largely determined by the affinity of Cu ion for amino group. It is indicated that this additional interaction with amino groups can influence the character of some amino acid complexes in biological systems