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An ENDOR Study of Nitrosyl Myoglobin Single Crystals
Author(s) -
Kappl R.,
Hüttermann J.
Publication year - 1989
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.198900011
Subject(s) - chemistry , myoglobin , crystallography , single crystal , hyperfine structure , ligand (biochemistry) , spectral line , anisotropy , histidine , proton , molecule , nuclear magnetic resonance , atomic physics , physics , biochemistry , receptor , organic chemistry , quantum mechanics , astronomy , amino acid
14 N, 15 N and 1 H ENDOR spectra were taken from single crystals of 15 NO ligated myoglobin at about 5 K in order to probe the spatial arrangement of the protons and nitrogens from the environment interacting with the Fe‐N‐O complex and to analyze its bonding configuration. The 14 N hyperfine (20.4 MHz, 15.2 MHz and 16.8 MHz) and quadrupolar tensors (+1.67 MHz, −0.86 MHz, −0.98 MHz) of NE2 of the proximal histidine expand the previously reported picture from ESR analysis showing a distorted NO bond configuration. 15 N data of the N(NO) ligand indicate, however, an orientation of the NO ligand differing from previous ESR reports. The single crystal spectra are applied to an interpretation of the more complex powder‐type spectra. Nine different 1 H interaction tensors have been analyzed and assigned on the basis of theoretical simulation of the single crystal gamut of line positions. For the distal NE2 bound histidine proton, a small position distribution, combined with a strong anisotropy of interaction, is shown to broaden the ENDOR patterns beyond detection. The consequences of this finding with respect to the tetrameric molecule hemoglobin are discussed.