Abstract
In photosynthesis, primary processes occur in photosystems composed of light-harvesting antenna complexes (LHs) and reaction centers (RCs). Most purple photosynthetic bacteria contain bacteriochlorophyll(BChl)-a, while some bacteria contain BChl-b whose Qy-absorption band is more red-shifted than that of BChl-a.
In this study, we isolated two types of RCs from Rhodobacter sphaeroides 2.4.1 containing BChl-a and Blastochloris (Rhodopseudomonas) viridis DSM133 containing BChl-b. In order to examine the effect of molecular structures of composite BChls upon the photoreaction efficiency, we reconstructed photoreaction units according to the procedures reported by Miyake and his colleagues: BChl-a type RCs (λmax = 867 nm) and BChl-b type RCs (λmax = 973 nm) were embedded in L-α-phosphatidylcholine membranes together with either exogenous BChl-a (λmax = 771 nm) or Chl-a (λmax = 661 nm) as an energy-donating pigment. We measured the light-induced absorbance change and photocurrent response of the reconstructed photoreaction units.
