Iron normal mode dynamics in (nitrosyl)iron(II)tetraphenylporphyrin from X-ray nuclear resonance data.
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.
Rai
Brajesh K
BK
Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA.
Durbin
Stephen M
SM
Prohofsky
Earl W
EW
Sage
J Timothy
JT
Wyllie
Graeme R A
GR
Scheidt
W Robert
WR
Sturhahn
Wolfgang
W
Alp
E Ercan
EE
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
D006420:Hemeproteins; D008665:Metalloporphyrins; D009211:Myoglobin; C422656:nitrosyl(meso-tetraphenylporphyrinato)iron(II); D007501:Iron