Concerning the form of biochemically active vanadium.

A survey has been made of the descriptive chemistry of vanadium as it pertains to physiological environments. Taking into account the vanadium concentration, pH, coordinating ligands and chelates, presence of other cations, oxidation-reduction potentials and the kinetics of the various vanadium-containing species, the following suggestions are made. Free vanadium ions will be monomeric. Monomeric vanadium(V) and vanadium(IV) will each exist in a specific hydrated form. Extracellular vanadium will be in the vanadate, Vv, form. Intracellular vanadium will most likely be predominantly in the vanadyl, Viv, form. Both extracellular vanadium(V) and intracellular vanadium(IV) will be bound to bi- or tridentate ligands if at all. If oxidation-reduction processes involving vanadium are fast relative to transmembrane transport, the transmembrane potential will not be coupled to the Vv/Viv Nernstian potential.