ABSTRACT
This chapter describes the most intriguing feature places the H. modesticaldum reaction center apart from the Photosystem I (PSI), Photosystem II (PSII), and purple bacterial reaction centers, all of which use a quinone as the electron acceptor. PSII is the second membrane-embedded reaction center pigment protein found in the plants, algae, and cyanobacteria and, from the point of view of electron transfer, is the most complex of the three reaction centers. The chapter provides a basic introduction to the three types of photochemical reaction center (RC) that have been utilized for bio-photovoltaics. The majority of studies of the photovoltaic capacities of purple bacterial proteins have utilized the heavily studied reaction center complex from Rba. sphaeroides or the larger purple bacterial proteins (RC-LH1)complex. The vulnerability of PSII to damage during turnover is one reason why exploration of its use in photovoltaic devices has been less extensive than has been the case for PSI or purple bacterial reaction center.
