title: Hydrogen bonding to the bound dioxygen in oxy cobaltous myoglobin reduces the superhyperfine coupling to the proximal histidine.
abstract: Electron spin echo envelope modulation (ESEEM) spectroscopy was used to study the electron-nuclear coupling in two oxygenated cobalt-substituted hemoproteins, myoglobin (oxyCoMb) and a monomeric hemoglobin from Glycera dibranchiata (oxyCoHbgly). The modulation frequency components in ESEEM spectra of both proteins arose from the coupling to the N epsilon of the proximal histidyl imidazole. The hyperfine and quadrupole coupling parameters for these two nitrogens, calculated by computer spectral simulation, are Aiso = 2.46 MHz, e2qQ = 2.15 MHz, and eta = 0.4 for oxyCoMb and Aiso = 3.70 MHz, e2qQ = 2.70 MHz, and eta = 0.5 for oxyCoHbgly. A hyperfine coupling of 0.6 MHz, found for oxyCoMb in D2O but not for oxyCoHbgly in D2O, was assigned to the coupling to a deuteron that is hydrogen-bonded to the O2 ligand in oxyCoMb. This hydrogen bonding is believed to be responsible for the reduction in hyperfine and nuclear quadrupole coupling to the proximal histidyl imidazole N epsilon in oxyCoMb. A molecular orbital model for O2 adducts of cobaltous compounds [Tovrog et al. (1976) J. Am. Chem. Soc. 98, 5144] was used to understand the hydrogen bond-induced reduction in 14N superhyperfine coupling in oxyCoMb.
authors.affiliation: Department of Molecular Pharmacology, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York 10461.
authors.forename: H C
authors.initials: HC
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Ikeda-Saito
authors.forename: T
authors.initials: T
authors.lastname: Yonetani
authors.forename: R S
authors.initials: RS
authors.lastname: Magliozzo
authors.forename: J
authors.initials: J
authors.lastname: Peisach
mesh_terms: D000818:Animals; D000845:Annelida; D003035:Cobalt / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005583:Fourier Analysis; D006639:Histidine; D006736:Horses; D006860:Hydrogen Bonding; D008433:Mathematics; D008962:Models, Theoretical; D009211:Myoglobin / Q000737:chemistry / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism*; D010108:Oxyhemoglobins / Q000737:chemistry / Q000378:metabolism; D014907:Whales
chemical_list: D009211:Myoglobin; D010108:Oxyhemoglobins; C017595:oxymyoglobin; D003035:Cobalt; D006639:Histidine; D010100:Oxygen