Abstract Details

Geometric and Electronic Structure of the Heme-Peroxo-Copper Complex [(F8TPP)FeIII-(O22-)-CuII(An)][B(C6F5)4]
Abstract ID	BIO-10
Presenter	Munzarin  Qayyum
Presentation Type	Poster
Full Author List	Munzarin Qayyum (1) , Matthew Kieber-Emmons (1) , Ritimukta Sarangi (2) , Thirumavelan Gandhi (3) , Kenneth D. Karlin (3) , Britt Hedman (2) , Keith O. Hodgson (1,2) , Edward I. Solomon (1)
Affiliations	(1) Dept. of Chemistry, Stanford University (2) Stanford Synchrotron Radiation Laboratory (3) Dept. of Chemistry, The Johns Hopkins University
Category	Bio/Life Sciences
Abstract	The active site of cytochrome c oxidase (CcO), the terminal enzyme in the respiratory chain, is comprised of a binuclear heme a3-CuB center where dioxygen reduction takes place. We have initiated a detailed Cu and Fe K-edge and EXAFS study on a series of heme-copper bridged, heteronuclear complexes that structurally mimic the active site of CcO to elucidate the nature of peroxide binding and cleavage. Our focus is to extend the work done on [(F8TPP)FeIII-(O22-)-CuII(TMPA)](ClO4) (1)1 to [(F8TPP)FeIII-(O22-)-CuII(An)][B(C6F5)4] (2) and similar systems. Using Cu and Fe K-edge EXAFS the Cu•••Fe distance of 1 was found to be ~3.72 Å with the peroxo unit bound end-on to the copper, and side-on to iron, for an overall µ-eta1:eta2 coordination mode. The Fe and Cu K-edge EXAFS data of 2 on the other hand provides a Cu•••Fe distance of ~3.65 Å. The peroxo unit is bound side-on to both copper and iron, for an overall µ-eta2:eta2 coordination mode. These XAS studies have been complemented by DFT calculations to derive a detailed description of O2 activation and cleavage, and the results using the combined information will be presented.
Footnotes	1 Rio, D. D.; Sarangi, R.; Chufan, E. E.; Karlin, K. D.; Hedman, B.; Hodgson, K. O.; Solomon, E. I. J. Am. Chem. Soc. 2005, 127 (34), 11969–11978.
Funding Acknowledgement	The work was performed at Stanford Synchrotron Radiation Laboratory (SSRL) with support from the NIH NCRR BTP program and the US DOE BER. SSRL operations are funded by the US DOE BES.