Bonding in HNO-myoglobin as characterized by X-ray absorption and resonance raman spectroscopies |
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Authors: | Immoos Chad E Sulc Filip Farmer Patrick J Czarnecki Kazimierz Bocian David F Levina Aviva Aitken Jade B Armstrong Robert S Lay Peter A |
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Affiliation: | Department of Chemistry, University of California, Irvine, California 92697-2025, USA. |
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Abstract: | The EXAFS and resonance Raman spectra on the HNO-myoglobin adduct, 1, are consistent with the presence of HNO bound to a heme center. The three-dimensional structure about the heme center of 1 obtained from multiple-scattering (MS) analysis of the EXAFS of the heme protein yielded an Fe-N-O bond angle of 131 degrees and an Fe-N bond length of 1.82 A, which compare well with published values for model complexes containing RNO ligands. Resonance Raman spectra identified the nu(N=O) stretch at 1385 cm-1 (confirmed by 15N labeling), which corresponds well with those reported for small molecule HNO complexes. The wavelength of the nu(Fe-N) at 636 cm-1 of 1 is significantly higher than those of MbIINO and MbIIINO (554 and 595 cm-1, respectively). The XAFS, XANES, and resonance Raman data are all consistent with the structure deduced from the NMR experiments, providing more detail on the bonding between HNO and the metal center. |
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