Vanadium Complexes as Prospective Therapeutics: Structural Characterization of a VIV Lysozyme Adduct

The biological activity of vanadium complexes, namely, as insulin enhancers, is well known. We report a combined X-ray crystallography, electron paramagnetic resonance, and density functional theory study of the interaction of vanadium picolinate complexes with hen egg white lysozyme (HEWL). We show that the VIVO(pic)2 complex covalently binds to the COO– group of the side chain of Asp52 of HEWL. The long VIV=O bond obtained in the X-ray study is explained to be due to reduction of VIV to VIII during exposure of the crystals to the intense X-ray beam.