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High sensitivity of the fluorine NMR signals of difluorovinyl analogs of natural hemin: reconstituted heme proteins and self‐exchange electron transfer in model compounds
Author(s) -
Poliart Christine,
Briand JeanFrancois,
Tortevoie Frédérique,
Leroy Jacques,
Simonneaux Gérard,
Bondon Arnaud
Publication year - 2001
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.899
Subject(s) - chemistry , heme , hemin , porphyrin , chemical shift , reaction rate constant , myoglobin , ligand (biochemistry) , solvent , electron transfer , hemeprotein , ferrous , ferric , metal , outer sphere electron transfer , fluorine 19 nmr , fluorine , chloroform , inorganic chemistry , nuclear magnetic resonance spectroscopy , photochemistry , stereochemistry , organic chemistry , kinetics , ion , biochemistry , physics , receptor , quantum mechanics , enzyme
Abstract The chemical shifts of fluorine in difluorovinyl deuteroporphyrin iron complexes were shown to be very sensitive to the spin state of the metal and the nature of the ligand(s). Reconstituted myoglobin was used as a model heme protein with an exchangeable heme. Large variations in the fluorine chemical shifts in both the ferric and ferrous states were observed. This strong sensitivity to the nature of the metal ligand and the structural resemblance to natural hemin make this fluorinated porphyrin a good probe for the study of heme proteins. The large variations of chemical shifts depending on the oxidation state also permitted the measurement of the electron self‐exchange rate constants of bis(1‐methylimidazole)iron complexes in various solvents by analysis of line broadening of the 19 F NMR signals. The experimental rate constants were strongly affected by the nature of the solvent, varying from 3.9 × 10 7 to 24.1 × 10 8 mol l −1 s −1 for DMSO‐ d 6 and acetone‐ d 6 , respectively. The solvent parameters were used to estimate the outer‐sphere reorganization energies. The experimental rate constants in chloroform and in DMSO are in good agreement with these calculated outer‐sphere reorganization energies. Copyright © 2001 John Wiley & Sons, Ltd.