Abstract Details

Electronic Structure Contributions to Electron Transfer by Heme Sites
Abstract ID	BIO-08
Presenter	Xiangjin  Xie
Presentation Type	Poster
Full Author List	X. Xie (1) , Y. Yan (1) , E. I. Solomon (1, 2)
Affiliations	(1) Department of Chemistry, Stanford University (2) Stanford Synchrotron Radiation Laboratory, Stanford Linear Accelerator Center, Stanford University
Category	Bio/Life Sciences
Abstract	Our photoelectron spectroscopic studies on heme model systems have provided critical experimental data that define their electronic structures and changes that occur upon redox. The Fe 2p photoelectron spectra of the low spin Fe(II) and Fe(III) heme complexes [Fe(tpp)(ImH)2] and [Fe(tpp)(ImH)2]Cl have been examined. These spectra are compared to those obtained from a series of iron complexes: [FeCl6]4-/3-, [Fe(tacn)2]2+/3+ and [Fe(CN)6]4-/3- allowing a quantitative determination of the difference between heme and non-heme Fe sites (low and high spin, Oh and Td coordination geometry) in the 2p shape-up region. Combining the PES data with a valence bond configuration interaction (VBCI) analysis and density functional theory (DFT) calculations, we have evaluated the electronic relaxation and the electron delocalization in the heme site and their contribution to electron transfer by the cytochromes. These photoelectron data coupled with our L-edge back bonding studies and analyzed using an extended charge decomposition analysis we developed reflect the significant contribution of the heme electronic structure to efficient electron transfer in biological systems.
Footnotes
Funding Acknowledgement	This research was supported by NSF Grants CHE-0446304(E.I.S.). PES experiments were performed at SSRL which is funded by the Department of Energy, Office of Basic Energy Sciences.