title: Direct probe of iron vibrations elucidates NO activation of heme proteins.
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.
authors.affiliation: Department of Physics and Center for Interdisciplinary Research on Complex Systems, Northeastern University, Boston, Massachusetts 02115, USA.
authors.forename: Weiqiao
authors.initials: W
authors.lastname: Zeng
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Silvernail
authors.forename: David C
authors.initials: DC
authors.lastname: Wharton
authors.forename: Georgi Y
authors.initials: GY
authors.lastname: Georgiev
authors.forename: Bogdan M
authors.initials: BM
authors.lastname: Leu
authors.forename: W Robert
authors.initials: WR
authors.lastname: Scheidt
authors.forename: Jiyong
authors.initials: J
authors.lastname: Zhao
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sturhahn
authors.forename: E Ercan
authors.initials: EE
authors.lastname: Alp
authors.forename: J Timothy
authors.initials: JT
authors.lastname: Sage
mesh_terms: D006420:Hemeproteins / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D009569:Nitric Oxide / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D014732:Vibration
chemical_list: D006420:Hemeproteins; D009569:Nitric Oxide; D007501:Iron