X-ray absorption spectroscopy of a structural analogue of the oxidized active sites in the sulfite oxidase enzyme family and related molybdenum(V) complexes.

X-ray absorption spectroscopy (XAS) (edge and extended X-ray absorption fine structure (EXAFS)) has been applied to the characterization of three molybdenum(V,VI) monodithiolene complexes with unidentate coligands, MoO(SC(6)H(2)-2,4,6-Pr(i)()(3))(2)(bdt) (1), MoOCl(SC(6)H(2)-2,4,6-Pr(i)(3))(bdt) (2), and MoO(2)(SC(6)H(2)-2,4,6-Pr(i)(3))(bdt) (3) (bdt = benzene-1,2-dithiolate). These complexes are related to the active site in the xanthine oxidase and sulfite oxidase families and, as in the enzyme sites, bind monodentate thiolate. By comparison to the data of crystalline oxidized chicken sulfite oxidase, it is shown that complex 3, whose thiolate simulates binding by the highly conserved cysteine, is an accurate structural analogue of the oxidized site of this enzyme. Normalized edge spectra, EXAFS data, Fourier transforms, and GNXAS-based fit results are presented. As in earlier studies, this provides characterization of new analogue complexes by XAS to facilitate identification of related sites in proteins.