Models for the active site of vanadium-dependent haloperoxidases: insight into the solution structure of peroxo vanadium compounds

A combined use of electrospray ionization-mass spectrometry (ESI-MS), V-51 NMR spectroscopy and ab initio calculations has been proved to be a powerfu l tool for obtaining direct information of the structure and the chemistry of peroxo vanadates in solutions. The analysis of acid solutions containing monoperoxo vanadates showed the occurrence of exchange reactions between s olvent molecules in the coordination sphere of the metal. On the other hand , bisperoxo vanadates appear to be less prone to coordinate more than one w ater or alcohol molecule. The bisperoxo complex [VO5](-) in the presence of histidine and histidine-like ligands, at near neutral conditions, has been studied. Coordination of one and two molecules of ligand is observed affor ding [VO5L](-) and [VO5L2](-), respectively. Characterization of these spec ies has been obtained by MSn experiments, which allowed us to distinguish s pecific fragmentations of the peroxidic moiety. (C) 2000 Elsevier Science I nc. All rights reserved.