title: Iron normal mode dynamics in (nitrosyl)iron(II)tetraphenylporphyrin from X-ray nuclear resonance data.
abstract: The complete iron atom vibrational spectrum has been obtained by refinement of normal mode calculations to nuclear inelastic x-ray absorption data from (nitrosyl)iron(II)tetraphenylporphyrin, FeTPP(NO), a useful model for heme dynamics in myoglobin and other heme proteins. Nuclear resonance vibrational spectroscopy (NRVS) provides a direct measurement of the frequency and iron amplitude for all normal modes involving significant displacement of (57)Fe. The NRVS measurements on isotopically enriched single crystals permit determination of heme in-plane and out-of-plane modes. Excellent agreement between the calculated and experimental values of frequency and iron amplitude for each mode is achieved by a force-field refinement. Significantly, we find that the presence of the phenyl groups and the NO ligand leads to substantial mixing of the porphyrin core modes. This first picture of the entire iron vibrational density of states for a porphyrin compound provides an improved model for the role of iron atom dynamics in the biological functioning of heme proteins.
authors.affiliation: Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA.
authors.forename: Brajesh K
authors.initials: BK
authors.lastname: Rai
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Durbin
authors.forename: Earl W
authors.initials: EW
authors.lastname: Prohofsky
authors.forename: J Timothy
authors.initials: JT
authors.lastname: Sage
authors.forename: Graeme R A
authors.initials: GR
authors.lastname: Wyllie
authors.forename: W Robert
authors.initials: WR
authors.lastname: Scheidt
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sturhahn
authors.forename: E Ercan
authors.initials: EE
authors.lastname: Alp
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D006420:Hemeproteins / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D008665:Metalloporphyrins; D008956:Models, Chemical; D015394:Molecular Structure; D009211:Myoglobin / Q000737:chemistry; D013057:Spectrum Analysis / Q000379:methods; D013816:Thermodynamics; D014965:X-Rays
chemical_list: D006420:Hemeproteins; D008665:Metalloporphyrins; D009211:Myoglobin; C422656:nitrosyl(meso-tetraphenylporphyrinato)iron(II); D007501:Iron