In order to explore the structure-activity relationship and molecular mechanism of the specific recognition between peroxovanadium. (pV) complexes bearing organic ligands and the target enzymes of tyrosine phosphatase, several NMR techniques and ESI-MS were used to study the interactions of four pV complexes {pV(ox), pV(bipy), pV(phen) and pV(pic), where pV=[VO(O-2)(2)L](n-), in which L=oxalic acid dianion (ox), bipyridine (bipy), 1, 10-phenanthroline (phen), and pyridine-2-carboxylic acid (pic)} towards histidine, Strong coordination interactions between imidazole of histidine and vanadium of pV(ox) or pV(pic) were observed in neutral solution, while there are not obvious interactions between histidine and pV(bipy) or pV (phen). All C-13 and H-1 NMR signals of 1:1 stoichiometric mixture of pV (ox) and histidine were assigned. Spectroscopic studies demonstrated that new complexes in the mixture of pV (ox) and histidine are a pair of isomers in which the vanadium in pV(ox) binding to the 3-N and 1-N of the imidazole ring. Moreover, the results of effective factors on the interaction system indicated that the new isomers were stable under the condition of physiological pH and the structure-activity relationship of these pV complexes may be relevant to their specific recognition towards histidine residues in tyrosine phosphatase
