title: Nitrite binding to globins: linkage isomerism, EPR silence and reductive chemistry.
abstract: The nitrite adducts of globins can potentially bind via O- or N- linkage to the heme iron. We have used EPR (electron paramagnetic resonance) and DFT (density functional theory) to explore these binding modes to myoglobin and hemoglobin. We demonstrate that the nitrite adducts of both globins have detectable EPR signals; we provide an explanation for the difficulty in detecting these EPR features, based on uniaxial state considerations. The EPR and DFT data show that both nitrite linkage isomers can be present at the same time and that the two isomers are readily interconvertible in solution. The millisecond-scale process of nitrite reduction by Hb is investigated in search of the elusive Fe(II)-nitrite adduct.
authors.affiliation: "Babeş-Bolyai" University, 1 Mihail Kogalniceanu str., RO-400084 Cluj-Napoca, Romania; Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK. Electronic address: rsilaghi@chem.ubbcluj.ro.
authors.forename: Radu
authors.initials: R
authors.lastname: Silaghi-Dumitrescu
authors.affiliation: Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK.
authors.forename: Dimitri A
authors.initials: DA
authors.lastname: Svistunenko
authors.affiliation: "Babeş-Bolyai" University, 1 Mihail Kogalniceanu str., RO-400084 Cluj-Napoca, Romania.
authors.forename: Daniela
authors.initials: D
authors.lastname: Cioloboc
authors.affiliation: "Babeş-Bolyai" University, 1 Mihail Kogalniceanu str., RO-400084 Cluj-Napoca, Romania.
authors.forename: Cristina
authors.initials: C
authors.lastname: Bischin
authors.affiliation: "Babeş-Bolyai" University, 1 Mihail Kogalniceanu str., RO-400084 Cluj-Napoca, Romania.
authors.forename: Florina
authors.initials: F
authors.lastname: Scurtu
authors.affiliation: Department of Biological Sciences, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK.
authors.forename: Chris E
authors.initials: CE
authors.lastname: Cooper
mesh_terms: D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005914:Globins / Q000378:metabolism*; D007536:Isomerism; D009573:Nitrites / Q000378:metabolism*; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet
chemical_list: D009573:Nitrites; D005914:Globins
keywords: DFT; EPR; Hemoglobin; Myoglobin; Nitrite