INTERACTION OF THE VANADYL(IV) CATION WITH CARNOSINE AND RELATED LIGANDS

The interaction of the vanadyl (IV) (VO2+) cation with carnosine (the dipeptide beta-alanyl-histidine) has been investigated by electron abs orption spectroscopy at high ligand-to-metal ratios and at different p H values. The results show that in the range 6.0-8.5, the cation inter acts with the imidazole group of four different carnosine molecules an d points to the presence of an axially coordinated water molecule. The se suppositions were confirmed by the behavior of the VO2+/imidazole s ystem, which was investigated under similar experimental conditions, a nd supported by previous ENDOR (electron-nuclear double resonance) res ults. The study was complemented with additional measurements using th e glycylglycine, glycylglycine/imidazole, and histidine systems as lig ands.