Direct probe of iron vibrations elucidates NO activation of heme proteins

J Am Chem Soc. 2005 Aug 17;127(32):11200-1. doi: 10.1021/ja051052x.

Abstract

We use nuclear resonance vibrational spectroscopy (NRVS) to identify the Fe-NO stretching frequency in the NO adduct of myoglobin (MbNO) and in the related six-coordinate porphyrin Fe(TPP)(1-MeIm)(NO). Frequency shifts observed in MbNO Raman spectra upon isotopic substitution of Fe or the nitrosyl nitrogen confirm and extend the NRVS results. In contrast with previous assignments, the Fe-NO frequency of these six-coordinate complexes lies 70-100 cm-1 lower than in the analogous five-coordinate nitrosyl complexes, indicating a significant weakening of the Fe-NO bond in the presence of a trans imidazole ligand. This result supports proposed mechanisms for NO activation of heme proteins and underscores the value of NRVS as a direct probe of metal reactivity in complex biomolecules.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Hemeproteins / chemistry*
  • Iron / chemistry*
  • Nitric Oxide / chemistry*
  • Nuclear Magnetic Resonance, Biomolecular
  • Vibration

Substances

  • Hemeproteins
  • Nitric Oxide
  • Iron