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PubMedDate not supplied

[Delayed bacteriochlorophyll luminescence and the primary stages of electron transport in photosynthetic reaction centers of purple bacteria].

The results of studies of charge separation in photosynthetic reaction centers of purple bacteria are summarized. The findings concerning the sequence of initial steps of the electron transfer and properties of the electron carriers obtained by direct methods of differential optical absorption and ESR spectroscopy are compared with the data on the bacteriochlorophyll delayed fluorescence resulting from reversal of charge separation. The data analysis gives an integrated description of the reaction center operation which is not avoid of discrepancies.

Bacteria↗
PubMedDate not supplied

[Study of the state of intracellular iron in photosynthesizing purple sulfur bacteria using the Mossbauer effect].

The work presents the results of the first stage of the study on the valent and structural state and function of the iron atoms in the donor-acceptor environment of the photosynthetic reaction centres of purple bacteria. 57Fe was introduced by cultivating the microorganisms in a medium enriched in this isotope. At 77 K the maxima observed in the Mössbauer spectra in intact freeze-dried cells at a speed of +2 mm/s and --1 mm/s are attributed to doublets 1.11 with the isomer ahifts of 1.3 and 0.5 mm/s respectively and the constants of the quadrupole splitting (Q.S.) of 2 mm/s and 2.2 mm/s. These are presumed to arise from cytochromes type c. The Mössbauer parameters of the intense assymetric quadrupole-split doublet of a more complex nature in the mid of the spectrum with line widths of 0.5 to 7.0 mm/s and 0.5 to 1.5 mm/s fit to these of bacterial ferredoxin. From the analysis of the control and dithionite-treated samples of the temperature dependency of the observable parameters over a temperature range of 77 to 300 K it can be concluded that in cells the iron atoms are present in various valency and spin states and the relation between the redox states of the iron atoms is dependent, in particular, on the age of the culture. The Mössbauer spectra of the cell fragments indicate that most of the intracellular iron, first of all the heme iron, is bound to the fraction of photosynthetic membranes.

Bacterial Chromatophores↗
PubMed1983

[High potential iron-sulfur protein from Thiocapsa roseopersicina].

A high potential protein (HiPIP) containing a [4Fe-4S] cluster was obtained in a homogeneous state from the purple sulfur bacterium T. roseopersicina strain BBS. The EPR and absorption spectra are specific for this type of proteins. In the absorption spectrum the A283/A390 ratio equals to 2.25; Mr = 10 000, pI is 4.08, E0' = +328 mV. The reduced form of HiPIP was found to be more stable upon storage; T 1/2 is 40 min at 80 degrees C. HiPIP can be reduced by ascorbate, cysteine, 2-mercaptoethanol and sulfide as well as by formate, H2 and NADPH in the presence of corresponding enzymes. Chromatophores oxidize HiPIP in the light. This suggests that the latter takes part in the photosynthetic electron transfer chain of T. roseopersicina.

Chromatium↗
PubMed1980

[Effect of light intensity on the content of bacteriochlorophyll and on the growth of phototrophic marine sulfur bacteria].

Eight strains of Chromatiaceae isolated from marine sediments are cultivated under light intensities of 50-5000 lx. A decreased in the light intensity brings about an increase in the specific bacteriochlorophyll content and also in the length of development. In certain strains, the increase in pigment contents partly compensates for the loss in light intensity, up to the maximum concentration of bacteriochlorophyll. This mechanism is only a physiological compatibility which ensures the survival of these organisms under feeble light intensities.

Bacteriochlorophylls↗