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Active site conformation in myoglobin as determined by X‐ray absorption spectroscopy
Author(s) -
Zhang K.,
Reddy K. S.,
Bunker G.,
Chance B.
Publication year - 1991
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.340100402
Subject(s) - myoglobin , x ray absorption fine structure , chemistry , bond length , crystallography , absorption (acoustics) , debye–waller factor , debye , absorption spectroscopy , spectroscopy , extended x ray absorption fine structure , active site , analytical chemistry (journal) , materials science , diffraction , crystal structure , optics , physics , biochemistry , enzyme , organic chemistry , chromatography , quantum mechanics , composite material
X‐ray absorption fine structure experiments were performed to study structural and dynamic aspects of the active site of various forms of myoglobin. The structures determined for deoxyMb, MbCO, and MbO 2 are consistent with the structure established by X‐ray absorption fine structure experiment and X‐ray crystallography. The first shell of ferrous MbNO determined contains 5 nitrogens located at 2.02 Å and a short NO bond length of 1.76 Å. This study focuses on the change of the XAFS Debye–Waller factor with temperature, which is a measure of thermal and static disorder. It was found that the changes of Debye–Waller factor with temperature for the Mb proteins, except deoxyMb, are consistent with a simple Einstein model, in which a single frequency was assumed for the bond stretching modes. In contrast, the temperature dependence of deoxyMb cannot be fitted to the Einstein model and a large disorder was found at low temperatures, which indicates the existence of conformational substates of the active site.