Conclusions and Perspectives
- Model studies related to vanadium biochemistry: recent advances and perspectives
We hope the above discussion has clearly shown the importance of model studies for a deeper understanding of some fundamental aspects related to the relatively complex biochemistry of vanadium. These studies have revealed valuable information concerning vanadium metabolism, toxicity, detoxification and catalytic activity. They have also extended the coordination chemistry of vanadium, especially that of the vanadium(IV) and vanadium(V) oxocations, as a direct consequence of the use of a variety of new ligand types. Nevertheless, there are a number of very important and interesting problems that remain open.
A better understanding of vanadium metabolism requires new efforts to comprehend its transport in both anionic and cationic forms, and for the initial reduction processes of vanadium(V) to VO2+ in the gastrointestinal tract. It would also be interesting to obtain crystalline VO2+ complexes with glutathione and related ligands and to explore further the interaction of this oxocation with serum albumin, transferrin and ferritin. A better chemical characterization of excreted vanadium species also seems very important.
More detailed speciation studies, including the determination of stability constants, are necessary for a wider characterization of the VO2+/nucleotide systems.
Other efforts should be directed to structural information on oxovanadium(IV) saccharide complexes. It has not yet been possible to obtain single crystals adequate for crystallographic studies,69 therefore EXAFS studies, like those recently performed on iron-saccharide complexes,120 should be attempted. Studies on the interaction of the VO2+ cation with polysaccharides should also be expanded, as these systems are of particular biological importance.
The possible use of phosphonates and related ligands, as well as the combination of appropriate reducing/chelating systems for use in vanadium detoxification merits further exploration.
Most of the model systems so far investigated, are also good candidates for theoretical studies, which may be very useful for a better understanding of stability, electronic structures, and reactivity. Some recent examples of this type of work are the molecular modeling of vanadium peroxides121 and studies of the electronic structures of Amavadine models.122
It is a great pleasure to acknowledge the contributions of the colleagues and collaborators whose names appear in the references. Work from our laboratory reported here was supported by the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina (CONICET), the Comisión de Investigaciones Científicas de la Provincia de Buenos Aires and the Agencia Nacional de Promoción Científica y Tecnológica. The author is a member of the Research Career of CONICET.
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