The elucidation of the nature of the RC and its role in photosynthesis was initiated

by ground-breaking discoveries by pioneering researchers Crenigacestat in the field. This issue of Photosynthesis Research honors three scientists: Louis M. N. Duysens, Roderick K. Clayton, and George Feher, who contributed greatly to the early development of the concept of the RC in photosynthetic bacteria and who provided details of the structure and function of this important pigment protein. In his classic study of light-induced absorbance changes in photosynthetic bacteria, Duysens (1952) discovered a small change in the absorption spectrum of a pigment in whole cells of Rsp. rubrum that represented the reversible bleaching Ralimetinib manufacturer of a small fraction of the bacteriochlorophyll (BChl) present in the sample. He showed that this change was due to a photo-oxidation of a pigment which he designated P to represent a special pigment active in photosynthesis. This was the first spectroscopic evidence for the specialized BChl that we now know as P870, the primary electron donor in photosynthesis.

This experiment supported the idea of a photosynthetic unit proposed by Emerson and Arnold (1932) based on oxygen evolution studies in Chorella, where they showed that most of the chlorophyll present in the cell was not active in the initial photochemical reaction. The concept of the RC was further developed by Clayton in a series of pioneering experiments. He showed that the reversible bleaching occurred even at cryogenic temperatures (Arnold and Clayton 1960), a characteristic of the primary photochemistry. He discovered a particularly useful

mutant strain (called R-26) of Rhodopseudomonas sphaeroides (now Rhodobacter sphaeroides) lacking carotenoids in which bulk of the BChl pigments were more unstable than the pigments in the RC (Clayton and Smith 1960). Using this strain he found conditions under which much of the inactive BChl was irreversibly destroyed, unmasking the active pigment P870 which could be identified by its reversible bleaching upon light illumination (Clayton 1963). This led to the first isolation Etomidate of a soluble RC complex by treatment of the bacterial membranes with the detergent Triton X-100 (Reed and Clayton 1968). Further characterization of the RC protein and its primary reactants was accomplished by George Feher using biochemical techniques and magnetic resonance spectroscopy. The detergent—lauryl dimethyl amine oxide was used to purify the RC preparation allowing the determination of the cofactors—4 BChl, 2 BPhe, Fe2+, and ~2 UQ and the characterization of the 3 protein subunits called L, M, and H (Feher 1971; Okamura et al. 1974). Using EPR and ENDOR spectroscopy he was able to help identify the primary donor as a bacteriochlorophyll dimer (Feher et al. 1975) as proposed by Norris et al.