So→T1 infrared difference spectrum of the triplet state of the primary electron donor in Rb. sphaeroides photosynthetic bacterial reaction centers

✍ Scribed by J. Breton; E. Nabedryk

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 518 KB
• Volume: 213
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(93)89162-b

✦ Synopsis

Using steady-state light-induced FTIR difference spectroscopy, the vibrational spectrum of the triplet state of the primary electron donor (P) in Rb. sphaeroides R-26 reaction centers has been characterized for the first time. Comparison with the difference spectrum of the oxidation of P shows that the 9-keto C-O vibrations of the two bacteriochlorophyll molecules constituting P absorb at 1695 and 1682 cm-' while the 10a ester carbonyls absorb at 1749 and around 1740 cm-'. Bands at 1648 and 1619 cm-' are assigned to the free and hydrogen-bonded 2a acetyl C-O of P, respectively. All these bands are downshifted upon 'P formation. These data demonstrate that the triplet state is mostly delocalized over the two bacteriochlorophyll molecules of P.