INTER-CHROMOPHORE INTERACTIONS IN PIGMENT-MODIFIED AND DIMER-LESS BACTERIAL PHOTOSYNTHETIC REACTION CENTERS

The magnitudes of inter-chromophore interactions in bacterial photosyn thetic reaction centers are investigated by measuring absorption and S tark spectra of reaction centers in which monomeric chromophores are m odified and in a novel triplet mutant which lacks the special pair. Th e circular dichroism spectrum of the triple mutant reaction center was also measured. Only small changes in the spectroscopic properties are observed, as has also been found for several types of reaction center s in which the absorption or chemical properties of a chromophore are altered by site-specific mutations. We conclude that the electronic ab sorption, circular dichroism and Stark features of the special pair an d the monomeric chromophores in the reaction center are relatively ins ensitive to inter-chromophore interactions.