Photoelectron Spectroscopy and Density Functional Theory

Enzyme (resolution) Fold Angle (°) Sulfite Oxidase (1.9 Å) 6.6 and 7.0 Aldehyde Oxidoreductase (MOP) (oxidized) (1.28 Å) 16.6 Xanthine Dehydrogenase(2.1 Å) 20.1 and 14.3 Dimethyl Sulfoxide Reductase (1.3 Å) 18.2 and 33.1

Crystal structures of Mo-containing enzyme active sites show varying fold angles of the dithiolate ligand with Mo oxidation state. This "dithiolate-folding-effect" is proposed to assist in electron transfer and modulate the redox potential at the metal center. A larger fold angle is observed for oxidized enzyme centers.

Metallocene dithiolates, Cp2M(S2C2R2), provide insight for the electronic basis of the dithiolate-folding-effect.

Gas-phase XPS, along with UPS studies, are used to quantify bonding in each electronic configuration of the dithiolate-folding-effect.