Singlet and triplet absorption spectra of carotenoids bound in the reaction centers of <i>Rhodopseudomonas sphaeroides</i> R26

Abstract

The singlet and triplet state absorption spectra are reported for two carotenoids, methoxyneurosporene and spheroidene, incorporated into the reaction center protein of the photosynthetic bacterial carotenoidless mutant Rhodopseudomonas sphaeroides R26. The spectra for the two different carotenoid molecules are identical suggesting a strong interaction between the protein and the different chromophores. Combined effects of electrochromic band shifts and carotenoid structural changes are invoked to account for the spectral observations.