| Autor: |
Tang, J., Utschig, L. M., Poluektov, O., Thurnauer, M. C. |
| Zdroj: |
The Journal of Physical Chemistry - Part B; June 17, 1999, Vol. 103 Issue: 24 p5145-5150, 6p |
| Abstrakt: |
Electron-spin polarized (ESP) EPR spectra at W-band (95 GHz) were obtained for deuterated Fe-removed/Zn-substituted photosynthetic bacterial reaction centers (RCs) to investigate the influence of the rate of charge separation on the observed P+QA- charge separated state. Temperature dependent ESP EPR spectra for kinetically characterized Zn-substituted RCs from Rb. sphaeroides R-26 having different rates (kQ) of the electron transfer from the bacteriopheophytin to the quinone acceptor were obtained. The Zn−RCs exhibited either the native fast (200 ps)-1 kQ or a slow (3−6 ns)-1 kQ at 298 K as determined from transient optical measurements. Sequential electron-transfer polarization modeling of the polarized W-band EPR spectra obtained with these samples was used to address the reason for the differences in the electron-transfer rates. Herein, we report the kQ rate constant, the temperature dependence of kQ, and the reorganization energy for the P+H-QA and P+HQA- electron-transfer step determined from SETP modeling of the experimental spectra. The reorganization energy for the electron-transfer process between P+H-QA and P+HQA-, and not structural changes in the donor or acceptor, was found to be the dominant factor that is altered during Fe-removal procedures. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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