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iDEA: Drexel E-repository and Archives > Drexel Academic Community > College of Arts and Sciences > Department of Chemistry > Faculty Research and Publications (Chemistry) > 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

Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/2616

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
Appears in Collections:Faculty Research and Publications (Chemistry)

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