title: The cupric site in nitrous oxide reductase contains a mixed-valence [Cu(II),Cu(I)] binuclear center: a multifrequency electron paramagnetic resonance investigation.
abstract: Multifrequency electron paramagnetic resonance (EPR) spectra of the Cu(II) site in nitrous oxide reductase (N2OR) from Pseudomonas stutzeri confirm the assignment of the low field g value at 2.18 consistent with the seven line pattern observed at 9.31 GHz, 10 K. S-band spectra at 20 K are better resolved than the X-band spectra recorded at 10 K. The features observed at 2.4, 3.4, 9.31 and 35 GHz are explained by a mixed-valence [Cu(1.5)..Cu(1.5)] S = 1/2 species with the unpaired electron delocalized between two equivalent Cu nuclei. The resemblance of the N2OR S-band spectra to the spectra for the EPR-detectable Cu of cytochrome c oxidase suggests that the S-band spectrum for cytochrome c oxidase measured below 30 K may also contain hyperfine splittings from two approximately equivalent Cu nuclei.
authors.affiliation: Fakultät für Biologie, Universität Konstanz, FRG.
authors.forename: P M
authors.initials: PM
authors.lastname: Kroneck
authors.forename: W A
authors.initials: WA
authors.lastname: Antholine
authors.forename: J
authors.initials: J
authors.lastname: Riester
authors.forename: W G
authors.initials: WG
authors.lastname: Zumft
mesh_terms: D003300:Copper / Q000378:metabolism*; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D010088:Oxidoreductases / Q000378:metabolism*; D011549:Pseudomonas / Q000201:enzymology*
chemical_list: D003300:Copper; D010088:Oxidoreductases; C022763:nitrous oxide reductase