~Zopyright 1996 by Humana Press Inc. All rights of any nature whatsoever reserved, 0163-4984/96/5501-2-0079 $7.25 Interaction of the Vanadyl (IV) Cation with Carnosine and Related Ligands EVEUNA G. FERRER, PATRICIA A. M. WLI~S, AND ENR1QUE J. BARAN* Quimica lnorganica (QUINOR), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata (1900), Argentina Received June 21, 1995; Accepted November 20, 1995 ABSTRACT The interaction of the vanadyl (IV) (VO2+) cation with carnosine (the dipeptide [3-alanyl-histidine) has been investigated by electron absorption spectroscopy at high ligand-to-metal ratios and at different pH 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 and points to the presence of an axially coordinated water molecule. These suppositions were confirmed by the behavior of the VO2+/ imidazole system, which was investigated under similar experimental conditions, and supported by previous ENDOR (electron-nuclear double resonance) results. The study was complemented with addi- tional measurements using the glycylglycine, glycylglycine/imidazole, and histidine systems as ligands. Index Entries: Vanadyl (IV); carnosine; electronic spectra. INTRODUCTION Carnosine (~-alanyl-L-histidine; Fig. 1) is found in skeletal muscles and in some other tissues of all vertebrates. Although its function is unknown, it has been established that carnosine is a substrate of the enzyme carnosinase. This enzyme is activated and/or stabilized by dif- ferent metal cations and the hydrolysis of carnosine has been extensively investigated (1-3). The interaction of metallic cations with carnosine itself has also acquired certain interest (4-8). Recently, the interaction of carnosine with vanadate has been inves- tigated (9). In this paper, we present results of the interaction of this *Author to whom all correspondence and reprint requests should be addressed. Biological Trace Element Research 79 Vol. 55, 1996