Electron spin polarization of the oxidized primary electron donor in reaction centers of photosynthetic purple bacteria
- Leiden Univ. (Netherlands)
- Physical and Theoretical Chemistry Lab., Oxford (United Kingdom)
Fast time-resolved EPR spectroscopy is used to study electron spin polarization (ESP) in perdeuterated native, Fe{sup 2+}-containing reaction centers (RCs) of photosynthetic purple bacteria. The spin-correlated radical pair-(SCRP) model previously used to simulate ESP observed in Fe-depleted RCs is extended to include the large anisotropy arising from the magnetic interactions between Fe{sup 2+} and the reduced primary electron-acceptor quinone (Q{sub A}{sup .-}), which results in different quantization axes from the P{sup .+} and the (Q{sub A}{sup .-}Fe{sup 2+}) spins. Using spectral simulations, it is shown that the ESP spectrum is solely due to the P{sup .+} part of the spin-correlated radical pair [P{sup .+}(Q{sub A}{sup .-}Fe{sup 2+})], whereas the rapid decay of the spin-polarized signal is due to spin-lattice relaxation of the (Q{sub A}{sup .-}Fe{sup 2+}) complex. The simulations are very sensitive to the relative orientation of the g matrices of P{sup .+} and (Q{sub A}{sup .-}Fe{sup 2+}). Using orientation II of the g matrix of the oxidized primary donor P{sup .+}, the orientation of the g matrix of (Q{sub A}{sup .-}Fe{sup 2+}) is assessed. Finally, it is shown that the ESP spectrum of perdeuterated native, Fe{sup 2+}-containing RCs of Rhodopseudomonas (Rps) viridis is virtually identical to the spectrum obtained for perdeuterated native Rhodobacter (Rb.) sphaeroides. 55 refs., 5 figs., 4 tabs.
- OSTI ID:
- 219697
- Journal Information:
- Journal of Physical Chemistry, Journal Name: Journal of Physical Chemistry Journal Issue: 6 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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