[Study of primary photoprocesses in photosystem II of Chlamydomonas mutant strains by hole-burning spectroscopy].
The method of hole-burning in absorption spectra at helium temperatures has been applied to the study of primary photoprocesses in photosystem II (PS2) of Chlamydomonas reinhardii mutant strains 420/7 and N-154. The former is enriched in PS2 reaction centers (the chlorophyll a/P680 ratio is about of 50--70) and the latter presumably lacks the pheophytin molecule which is the primary electron acceptor in PS2. For the strain 420/7 samples with ferricyanide addition two types of holes have been observed differing in their width and spectral region of burning. One type could be burned in the region of 678--682 nm (P680 is responsible for burning) and another one -- in the region of 682--688 nm (pheophytin is responsible). The excited states relaxation times evaluated from the hole widths are 3,8 +/- 0,8 ps for P680 and 9,8 +/- 1.5 ps for pheophytin. The new mechanism of PS2 operating has been proposed in which photoexcited phenophytin molecule functions as a primary electron donor. In the case of N-154 strain the only type of holes has been observed for which P680 is responsible. The excited state relaxation time of the latter evaluated from the hole width is 10 +/- 2 ps.
D002696:Chlamydomonas / Q000235:genetics / Q000378:metabolism*; D004579:Electron Transport; D007700:Kinetics; D009154:Mutation; D010674:Pheophytins / Q000378:metabolism; D010788:Photosynthesis; D013053:Spectrophotometry / Q000379:methods; D013696:Temperature
D010674:Pheophytins
Issledovanie pervichnykh fotoprotsessov v fotosisteme 2 mutantov khlamidomonady metodom spektroskopii vyzhiganiia provalov.