Electron spin polarization model applied to sequential electron transfer in iron-containing photosynthetic bacterial reaction centers with different quinones as O{sub A}
- Argonne National Lab., IL (United States)
- Univ. of Pennsylvania, Philadelphia, PA (United States)
- City College of New York, NY (United States)
Electron spin polarization develops on P{sup +} [Fe{sup 2+}]{sup -} n iron-containing photosynthetic bacterial reaction centers (RC) of Rhodobacter sphaeroides. The spin-polarized electron paramagnetic resonance (EPR) spectra of the oxidized primary donor (P{sup +}) depend on {tau}{sub H}, the lifetime of the radical pair P{sup +}H{sup -} formed prior to P{sup +}[Fe{sup 2+}]{sup -}. The polarized EPR signal can be described by the sequential electron transfer polarization (SETP) model in which the chemically induced dynamic electron polarization (CIDEP) developed in P{sup +}H{sup -} is projected onto the correlated radical pair polarization (CRPP) developed in P{sup +}[Fe{sup 2+}]{sup -}. Replacing the native ubiquinone-10 with various anthraquinones and naphthoquinones alters both the free energy and rate of electron transfer from H{sup -} to QFe{sup 2+}, which in turn modifies {tau}{sub H}{minus}. At long {tau}{sub H}{minus}, the polarized P{sup +} EPR signal is dominated by the CIDEP component of SETP. At short {tau}{sub H}{minus}, the signal is dominated by the CRPP component, while at intermediate {tau}{sub H}{minus}`s the signal can only be described using the full SETP model. The ranges of {tau}{sub H}, where polarization is dominated by interactions on the prior or observed radical pair are influenced by the EPR microwave frequency and RC isotopic composition. 71 refs., 8 figs., 2 tabs.
- Research Organization:
- Argonne National Laboratory (ANL), Argonne, IL
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 35466
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 11 Vol. 99; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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