Probing the fluorescence emission kinetics of the photosynthetic apparatus of Rhodopseudomonas sphaeroides, strain 1760-1, on a picosecond pulse fluorometerстатья
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Дата последнего поиска статьи во внешних источниках: 31 декабря 2013 г.
Аннотация:Using the pulse picosecond fluorometric technique the fluorescence properties of intact cells, isolated chromatophores and photosynthetic reaction centres were studied in bacteria Rhodopseudomonas sphaeroides, strain 1760-1. The fluorescent emission from reduced reaction centres excited by 694.3 nm light has a biphasic character, the lifetimes of the components being t1 = 15+/-8 ps and t2 = 250 ps. The faster component, t1, contributes to the integral fluorescence in the long wavelength region. It disappears with oxidation of the reaction centres and is attributed to photoactive bacteriochlorophyll P870. The slow component, t, is apparently due to both bacteriochlorophyll P800 and bacteriopheophytin. The fluorescence from intact cells exhibits a monophasic pattern and decays with t = 200 ps. The fluorescence emitted by chromatophores comprises two components with t3 = 200 ps and t4 = 4200 ps. The duration of fluorescence t3 increases to its maximum of 500-550 ps, as P870 is oxidized chemically or photochemically, while t4 remains unchanged. The fluorescence with a lifetime of 200 ps was ascribed to the photosystem and the 4200 ps fluorescence to bacteriochlorophyll which had lost its functional links with the photosystem. The rise time of the fluorescence emitted by chromatophores varies from 60 or 70 ps to 350 ps depending on the wavelength of the exciting light and the recorded spectral region. On the basis of our findings the rate for energy migration was estimated to be 109 sтИТ1.