STEP-SCAN FT-IR SPECTROSCOPY OF ELECTRON-TRANSFER IN THE PHOTOSYNTHETIC BACTERIAL REACTION-CENTER

Step-scan light-induced FT-IR difference spectra (1800 1200 cm-1) of R hodobacter sphaeroides photosynthetic bacterial reaction centers at lo w temperature and with a 10-mus time resolution are presented. The mol ecular changes and relaxation processes accompanying the photoxidation of the primary electron donor (P) are already present 10 mus after ex citation. The photoconversion of P to the triplet state gives rise to characteristic IR absorption changes which decay with a half-time of 1 30 mus. A negative band at 1695 cm-1 and a positive one at 1670 cm-1 a re assigned to the 9-keto carbonyl of bacteriochlorophyll in the state s P and P-3, respectively.