title: The binding of nitric oxide at the Cu(i) site of copper nitrite reductase and of inorganic models: DFT calculations of the energetics and EPR parameters of side-on and end-on structures.
abstract: Density functional theory calculations have been used to probe the end-on and side-on bonding motifs of nitric oxide at the Cu(i) centre in the enzyme copper nitrite reductase and in three inorganic model systems. We find that irrespective of a range of functionals used, the end-on structure is preferred by up to 40 kJ mol(-1), although this preference is smaller for the enzyme than for the inorganic model systems. We have calculated the g-tensor and atomic hyperfine coupling constants for these structures. When compared to available experimental data, for one model compound the calculated EPR parameters definitely favour an end-on structure, although this preference is somewhat less for the enzyme. Our prediction of NO end-on binding in the enzyme is at variance with structural data.
authors.affiliation: School of Chemistry, University of Manchester, Manchester, UKM13 9PL, UK.
authors.forename: Ganga
authors.initials: G
authors.lastname: Periyasamy
authors.forename: Mahesh
authors.initials: M
authors.lastname: Sundararajan
authors.forename: Ian H
authors.initials: IH
authors.lastname: Hillier
authors.forename: Neil A
authors.initials: NA
authors.lastname: Burton
authors.forename: Joseph J W
authors.initials: JJ
authors.lastname: McDouall
mesh_terms: D001665:Binding Sites; D003300:Copper / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D007700:Kinetics; D008958:Models, Molecular; D008968:Molecular Conformation; D009569:Nitric Oxide / Q000378:metabolism*; D009572:Nitrite Reductases / Q000737:chemistry* / Q000378:metabolism*; D011487:Protein Conformation
chemical_list: D009569:Nitric Oxide; D003300:Copper; D009572:Nitrite Reductases