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Asymmetric band profile of the Soret band of deoxymyoglobin is caused by electronic and vibronic perturbations of the heme group rather than by a doming deformation
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http://hdl.handle.net/1860/2616
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| Title: | Asymmetric band profile of the Soret band of deoxymyoglobin is caused by electronic and vibronic perturbations of the heme group rather than by a doming deformation |
| Authors: | Schweitzer-Stenner, Reinhard
Gorden, John Paul
Hagarman, Andrew |
| Issue Date: | 4-Oct-2007 |
| Publisher: | American Institute of Physics |
| Citation: | Journal of Chemical Physics, 127(13): pp. 135103 |
| Abstract: | We measured the Soret band of deoxymyoglobin deoxyMb , myoglobin cyanide MbCN , and
aquo-metmyoglobin all from horse heart with absorption and circular dichroism CD
spectroscopies. A clear non-coincidence was observed between the absorption and CD profiles of
deoxyMb and MbCN, with the CD profiles red- and blueshifted with respect to the absorption band
position, respectively. On the contrary, the CD and absorption profiles of aquametMb were nearly
identical. The observed noncoincidence indicates a splitting of the excited B state due to
heme-protein interactions. CD and absorption profiles of deoxyMb and MbCN were
self-consistently analyzed by employing a perturbation approach for weak vibronic coupling as well
as the relative intensities and depolarization ratios of seven bands in the respective resonance Raman
spectra measured with B-band excitation. The respective By component was found to dominate the
observed Cotton effect of both myoglobin derivatives. The different signs of the noncoincidences
between CD and absorption bands observed for deoxyMb and MbCN are due to different signs of
the respective matrix elements of A1g electronic interstate coupling, which reflects an imbalance of
Gouterman’s 50:50 states. The splitting of the B band reflects contributions from electronic and
vibronic perturbations of B1g symmetry. The results of our analysis suggest that the broad and
asymmetric absorption band of deoxyMb results from this band splitting rather than from its
dependence on heme doming. Thus, we are able to explain recent findings that the temperature
dependences of CO rebinding to myoglobin and the Soret band profile are uncorrelated
Ormos et al., Proc. Natl. Acad. Sci U.S.A. 95, 6762 1998 . |
| URI: | http://dx.doi.org/10.1063/1.2775931
http://hdl.handle.net/1860/2616 |
| Appears in Collections: | Faculty Research and Publications (Chemistry)
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