Determination of the quantum yields of the primary photosynthesis events and the photosynthetic unit types in purple bacteria

Abstract

Summarg1. Photoinduced changes in absorbancy and fluorescence yields were studied in Chromatium minutissium and Ectothiorhodospira Shaposhnikovii suspensions. These parameters were examined as functions of light intensity in the region of 750-950 nm under aerobic and anaerobic conditions. 2. The fluorescence was shown to consist of two spectrally indistinguishable emissions : "photosynthetic" emission with a yield correlating with the state of reaction centres (P890) and "background" emission with constant yield.3. The "photosynthetic" fluorescence dependence on the portion of nonactive Psg0 was consistent with the multicentral (statistic) model of photosynthetic unit organization.4. In anaerobic conditions the amplitude ofthe photoinduced absorbancy increase around 910 nm was proportional to the portion of nonactive P890. 5. A precise method for determinating the quantum yield of the primary electron donation was proposed. For Chr. minutissimum and E. shaposhnikovii under aerobic conditions these yields were found to be equal to 0.91 • 0.02 and 0.93 J= 0.02 respectively.

Excitation trapping by different states of photosynthetic reaction centres

“…In order to convert the main part of RCs to the active state PA redox agents should be added in order to have Em of the medium within 2.50-350 mV. Measurement of 7fl under these conditions by time-lever method [9,10] gives the values of 30-50 ps at low light intensity. Transition to the saturated light in this case converts RCs to one of the closed states, III(P'.A1 .…”

“…The number of dark oxidized RCs and those produced by light saturation under different conditions was determined with the instrument, described in [9].…”

Spectral and energetic characteristics of the photoactive particles obtained from chromatophores of the green bacterium Chlorobium limicola

“…4) by using method devised previously in our laboratory [7], we determined the quantum yield of photosynthesis ( fig. 5): g~ph ) 0,95 -0.…”

“…Light-induced absorption changes were registered as described elsewhere [7]. Absorption spectra were measured with the Hitachi EPS-3 spectrophotometer.…”

“…Both the supernatant mostly containing light particles enriched with BChla and the precipitate containing heavy particles were used in experiments. Light-induced absorption changes were registered as described elsewhere [7]. Absorption spectra were measured with the Hitachi EPS-3 spectrophotometer.…”