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 vibratio...

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Bibliographic Details
Published in:Biophysical journal 2002-06, Vol.82 (6), p.2951-2963
Main Authors: Rai, Brajesh K., Durbin, Stephen M., Prohofsky, Earl W., Sage, J. Timothy, Wyllie, Graeme R.A., Scheidt, W. Robert, Sturhahn, Wolfgang, Alp, E. Ercan
Format: Article
Language:English
Subjects:
Biochemistry
Biophysical Phenomena
Biophysics
Hemeproteins - chemistry
Iron
Iron - chemistry
Metalloporphyrins
Models, Chemical
Molecular Structure
Myoglobin - chemistry
NMR
Nuclear magnetic resonance
Scientific imaging
Spectrum Analysis - methods
Thermodynamics
X-Rays
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Summary: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 57Fe. 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.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(02)75636-1