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 (VO)-O-IV(pic)(2) complex covalently binds to the COO- group of the side chain of Asp52 of HEWL. The long V-IV=O bond obtained in the X-ray study is explained to be due to reduction of V-IV to V-III during exposure of the crystals to the intense X-ray beam.