Spectrophotometric Studies on the Primary Processes of Photosynthesis

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The Primary processes, i.e., energy transfer, photochemistry and electron transport of photosynthesis were investigated with a wide variety of spectrophotometric techniques. The materials used involved light-harvesting pigment-proteins and photochemically active preparations isolated from photosynthetic bacteria, cyanobacteria, algae and higher plants.P-700 was successfully reconstituted by adding chl a to chl-depleted PS I Particles and a structural role of antenna chl to stabilize PS I complexes was found for the first time (42). The differential absorption coefficient of P-700 was shown to be highly variable due to an electrochromic band shift of antenna chl a in detergent-treated PS I preparations (1,7). A stable Dl-D2-cyt. b-559 complex was prepared and the stoichiometry of subunit proteins and bound pigments were established (15).Binding of various synthetic quinones to quinone-binding sites of PS I (phylloquinone site) and PS II (*_B site) were investigated and structural parameters affecting the binding affinities of respective sites were determined (24, 25). A dark-stable S2 EPR signal and a new EPR signal derived from the S2 signal on illumination were found in inactivated oxygen evolving prepararions (17, 19). Efficiency of photoactivation of oxygen evolution was improved to a geat erxtent (21, 22) and His^+ was shown to serve as an oxidant of Mn during photoactivation (27). The emission spectrum of thermoluminescence was firstly determined (24, 25). Efficiency of energy transfer from carotenoids to bacteriochl was shown to decrease with increasing length and a distorted conformation of the conjugated double bond chains of carotenoids (54). Energy transfer in various photosynthetic organisms were intensively studied (64-72).