Vanadium Project at University of Michigan
Vanadium has been found to play a number of roles in biological systems. It is present in certain vanadium dependent haloperoxidase and nitrogenase enzymes. Many sea squirts accumulate vanadium in very high concentration, although the reason is not known. The Amanita muscaria mushrooms also accumulate vanadium in the form of a coordination complex called amavadin, whose function is also unknown. Finally, a number of vanadium complexes have been shown to alleviate many of the symptoms of diabetes in both in vitro and in vivo (in rats and mice) studies. These complexes are being studied as potential alternatives to insulin therapy.
Research in the Pecoraro group has concentrated primarily on designing spectroscopic and functional models for vanadium dependent haloperoxidases (VHPOs). VHPOs catalyze the 2-electron oxidation of a halide (X- = Cl-, Br-, or I-) by peroxide through a Lewis acid-promoted mechanism (as opposed to redox cycling at the vanadium center) as summarized in Scheme 1. A reactive halogenating species (HOX, X2, or X3-) is produced which can react with electron-rich substrates to form halogenated organic compounds. Vanadium remains in the +5 oxidation state throughout the entire catalytic cycle. When the vanadium is reduced to the +4 oxidation state, the enzyme is totally inactive.