Tunneling in Chromatium chromatophores: Detection of a Hopfield charge-transfer band
AUTOR(ES)
Goldstein, Robert F.
RESUMO
We have observed a weak charge-transfer band in the cytochrome c-P870 electron-transfer reaction in Chromatium vinosum chromatophores at 10 K and at 85 K. First, the intermediate acceptor, I, was trapped in the reduced state by lowering the redox potential at room temperature, then illuminating with white light at low temperature for 20 min. Next, illumination by broadband infrared (1-3 μm, 6.5 kW/m2) for 4 hr at 10 K decreased the I- electron spin resonance signal by 30%. One-hour infrared illumination at 85 K decreased the cytochrome c Soret band shift by 10%. The effect of infrared was to promote the system from the ground vibrational state with the electron on P870 to an excited vibrational state with the electron on cytochrome c. The absorption band peak is near 2 μm, and the integrated cross section is ≈6 × 10-3 eV·M-1·cm-1. These values are consistent with small (0.02 nm) nuclear motion and with electron-transfer rates measured in the dark.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=344625Documentos Relacionados
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