title: Pulsed EPR studies of the exchangeable proton at the molybdenum center of dimethyl sulfoxide reductase.
abstract: Electron spin echo envelope modulation (ESEEM) spectroscopy has been used to determine the hyperfine ( hfi) and quadrupole ( nqi) interactions of the exchangeable deuteron (proton) at the Mo(V) site of DMSO reductase. The data obtained have been translated into structure-related parameters. It was found that isotropic hfi constant of the proton is not unique, but is distributed within a range of 26-36 MHz. From this hfi distribution, a 30 degrees -wide distribution of the OH bond orientations due to a rotation around the Mo-O bond was estimated. The angle between the axes of the nqi and anisotropic hfi tensors was found to be anomalously small in comparison with that expected from the Mo-O-D bond geometry. This peculiarity was attributed to the effect of spin density on the hydroxyl oxygen atom. The orientation of the Mo-OH fragment with respect to the g-frame was determined from the experimental orientations of the nqi and hfi tensor axes and a theoretical evaluation of the anisotropic hfi axis direction.
authors.affiliation: Department of Chemistry, University of Arizona, Tucson, AZ 85721-0041, USA.
authors.forename: Arnold M
authors.initials: AM
authors.lastname: Raitsimring
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Astashkin
authors.forename: Changjian
authors.initials: C
authors.lastname: Feng
authors.forename: John H
authors.initials: JH
authors.lastname: Enemark
authors.forename: Kimberly Johnson
authors.initials: KJ
authors.lastname: Nelson
authors.forename: K V
authors.initials: KV
authors.lastname: Rajagopalan
mesh_terms: D003903:Deuterium / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D007506:Iron-Sulfur Proteins; D008958:Models, Molecular; D008982:Molybdenum / Q000737:chemistry*; D010088:Oxidoreductases / Q000737:chemistry*; D011522:Protons; D011994:Recombinant Proteins / Q000737:chemistry; D013329:Structure-Activity Relationship
chemical_list: D007506:Iron-Sulfur Proteins; D011522:Protons; D011994:Recombinant Proteins; D008982:Molybdenum; D003903:Deuterium; D010088:Oxidoreductases; C045664:dimethyl sulfoxide reductase