Study of the Molecular Interactions Between Polyoxometalates and Proteins

Various biochemical and biomedical techniques for the study of proteins require the fragmentation of these proteins. For this fragmentation to occur the extremely stable peptide bond should be hydrolyzed. Only a handful of reagents are commercially in use for this purpose. Since the cleaving agents that are currently used possess quite a few disadvantages, the focus of the research has shifted towards metal ions and their complexes during the past decade. Consequently, the focal point of the studies of our research group concerns the biomedical activity of polyoxometalates (POMs) towards biomolecules and their model systems. Recent studies have demonstrated the hydrolysis of the peptide bond in dipeptides, oligopeptides and proteins by metal-substituted POMs. Before this hydrolysis can occur, an interaction between the POM and the substrate is required. This interaction is of paramount importance for the determination of the effectiveness and specificity of the hydrolysis by POMs. For that reason, the interaction process between POMs and proteins has been examined by luminescence spectroscopy, fluorescence spectroscopy and molecular dynamics (MD) simulations. The interaction between Keggin type POMs and four proteins (human, HSA, and bovine serum albumin, BSA, hen egg white lysozyme, HEWL, and nbsp;α-LA) was studied by steady state and time-resolved Eu(III) luminescence and tryptophan (Trp) fluorescence spectroscopy. With these techniques it was possible to obtain the number of bound molecules per protein and to quantify the strength of the interaction. Moreover, Trp fluorescence spectroscopy was utilized to examine the interaction of a series of hydrolytically active Zr(IV)-substituted POMs and HSA. Finally, the interaction of a Ce(IV)-substituted Keggin POM towards HEWL was investigated by MD simulations.status: publishe