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Ozone model for bonding of an O2 to heme in oxyhemoglobin

Goddard, William A., III and Olafson, Barry D. (1975) Ozone model for bonding of an O2 to heme in oxyhemoglobin. Proceedings of the National Academy of Sciences of the United States of America, 72 (6). pp. 2335-2339. ISSN 0027-8424.

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Several rather different models of the Fe-O2 bond in oxyhemoglobin have previously been proposed, none of which provide a satisfactory explanation of several properties. We propose a new model for the bonding of an O2 to the Fe of myoglobin and hemoglobin and report ab initio generalized valence bond and configuration interaction calculations on FeO2 that corroborate this model. Our model is based closely upon the bonding in ozone which recent theoretical studies have shown to be basically a biradical with a singlet state stabilized by a three-center four-electron pi bond. In this model, the facile formation and dissociation of the Fe-O2 bond is easily rationalized since the O2 always retains its triplet ground state character. The ozone model leads naturally to a large negative electric field gradient (in agreement with Mossbauer studies) and to z-polarized (perpendicular to the heme) charge transfer transitions. It also suggests that the 1.3 eV transition, present in HbO2 and absent in HbCO, is due to a porphyrin-to-Fe transition, analogous to that of ferric hemoglobins (e.g., HbCN).

Item Type:Article
Additional Information:© 1975 by the National Academy of Sciences. Communicated by Harry B. Gray, February 19, 1975. We thank Drs. William Eaton and Philip Stephens for helpful discussions on the spectrum of hemoglobin. Computing assistance was obtained from the Health Sciences Computing Facility, UCLA, sponsored by the National Institutes of Health Special Resources Grant, RR-3. We thank Prof. Verne Schumaker and Dr. Patricia Britt for their assistance. This work was partially supported by Grant GP40783X from the National Science Foundation (to W.A.G.) and by predoctoral fellowships (to B.D.O.) from the National Science Foundation and the National Institutes of Health. This work is Contribution no. 5015 from the Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, Calif.
Subject Keywords:electronic structure; generalized valence bond; configuration interaction; excited electronic states; electric field gradient
Record Number:CaltechAUTHORS:GODpnas75
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9591
Deposited By: Tony Diaz
Deposited On:12 Feb 2008
Last Modified:14 Nov 2014 19:20

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