TY - JOUR
T1 - Iron-57 nuclear shieldings as a quantitative tool for estimating porphyrin ruffling in hexacoordinated carbonmonoxy heme model compounds in solution
AU - Kalodimos, Charalampos G.
AU - Gerothanassis, Ioannis P.
AU - Rose, Eric
AU - Hawkes, Geoffrey E.
AU - Pierattelli, Roberta
PY - 1999/3/31
Y1 - 1999/3/31
N2 - 57Fe NMR spectra of several carbonmonoxy hemoprotein models with varying polar and steric effects of the distal organic superstructure, constraints of the proximal side, and porphyrin ruffling are reported. 57Fe shieldings, δ(57Fe), vary by nearly 900 ppm among various hemes, and an excellent correlation was found between δ(57Fe) and the absolute crystallographic average displacement of the meso carbon atoms, |Cm|, relative to the porphyrin core mean plane. The great variation of δ(57Fe) as a function of |C(m)| (~140 ppm/0.1 Å) demonstrates that iron-57 shieldings can be used in structure refinement protocols for the extraction of more accurate structures for heme rings in heme model compounds. The excellent correlation between iron-57 shieldings and the average shieldings of the meso carbons of the porphyrin skeleton of TPP derivatives suggests that the two probes reflect similar types Of electronic and structural perturbations, which are primarily due to porphyrin ruffling. The present findings also emphasize the value in predicting 57Fe shieldings in superstructured metalloporphyrins from 13C shieldings of the meso carbons.
AB - 57Fe NMR spectra of several carbonmonoxy hemoprotein models with varying polar and steric effects of the distal organic superstructure, constraints of the proximal side, and porphyrin ruffling are reported. 57Fe shieldings, δ(57Fe), vary by nearly 900 ppm among various hemes, and an excellent correlation was found between δ(57Fe) and the absolute crystallographic average displacement of the meso carbon atoms, |Cm|, relative to the porphyrin core mean plane. The great variation of δ(57Fe) as a function of |C(m)| (~140 ppm/0.1 Å) demonstrates that iron-57 shieldings can be used in structure refinement protocols for the extraction of more accurate structures for heme rings in heme model compounds. The excellent correlation between iron-57 shieldings and the average shieldings of the meso carbons of the porphyrin skeleton of TPP derivatives suggests that the two probes reflect similar types Of electronic and structural perturbations, which are primarily due to porphyrin ruffling. The present findings also emphasize the value in predicting 57Fe shieldings in superstructured metalloporphyrins from 13C shieldings of the meso carbons.
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U2 - 10.1021/ja983889g
DO - 10.1021/ja983889g
M3 - Article
AN - SCOPUS:0033620368
SN - 0002-7863
VL - 121
SP - 2903
EP - 2908
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 12
ER -