title: Electron paramagnetic resonance of single crystal oxycobaltmyoglobin and deoxycobaltmyoglobin.
abstract: Single crystals of oxycobaltmyoglobin and deoxycobaltmyoglobin have been prepared and found to be isomorphous. The paramagnetic resonance spectra of deoxycobaltmyoglobin yield g(xx) = 2.33(0), g(yy) = 2.32(3), g(zz) = 2.02(8) with the z-axis parallel to the "heme" normal. The A(Co) and g tensors share the same principal axes with|A(Co) parallel| = 79 G and|A(Co)[unk]| = 6 G. A value of A(N) = 17.5 G was also obtained for the epsilon-N atom of the F8 histidine. There are two paramagnetic species in oxycobaltmyoglobin having apparently identical g-tensors (gxixi = 2.08(3), getaeta = 2.00(6), and gzetazeta = 1.98(9)) but different A(Co)-tensors. Furthermore, g values A(Co) do not share the same principal axes. The A(Co)-values for one of the species are (A(xx) = 16.7 G, A(yy) = 5.95 G, A(zz) = 9.3 G), they are all 40% larger for the other species. The two species are oriented 90 degrees to each other in the crystal. The results from electron paramagnetic resonance studies are consistent with a pi-bounded structure for (Co)MbO(2).
mesh_terms: D000818:Animals; D002591:Cetacea; D055598:Chemical Phenomena; D002621:Chemistry; D002850:Chromatography, Gel; D003035:Cobalt; D003461:Crystallography; D004578:Electron Spin Resonance Spectroscopy; D008968:Molecular Conformation; D009211:Myoglobin; D013056:Spectrophotometry, Ultraviolet
chemical_list: D009211:Myoglobin; D003035:Cobalt