[Singlet-triplet excitation fission in light-harvesting complexes of photosynthetic bacteria and in isolated carotenoids].

Time-resolved electron paramagnetic resonance was used to study the properties of carotenoid triplet states populated in LH2 light-harvesting complexes of phototrophic bacteria Allochromatium minutissimum, Rhodopseudomonas palustris, and in carotenoid films free of bacteriochlorophyll. The study was performed on purified LH2 preparations not contaminated by reaction centers, and under selective pigment excitation. The obtained results enable a conclusion that the carotenoid triplet states, both in LH2 complexes and films, are populated in the process of homofission of singlet excitation into two triplets, which involves only carotenoid molecules. It is observed that the fission process in magnetic field leads to predominant population of the T0 spin sublevel of the triplet. One molecular spin sublevel of the triplet is demonstrated to possess an increased probability of intersystem crossing to the ground state, independent of the carotenoid configuration. Pigment composition of the LH2 protein heterodimers is discussed, and a conclusion of the possible

[Triplet state of the primary donor in reaction centers of the phototrophic bacterium Rhodobacter sphaeroides R26 with active photoinduced electron transfer].

EPR characteristics of transient paramagnetic states photoinduced in isolated reaction centers of Rhodobacter sphaeroides R26 with intact electron transfer have been studied. It was demonstrated that the detected weak triplet state EPR signal belongs to the primary donor molecule and is populated via the conventional mechanism of radical pair S-T0 mixing. The distortion of the spectral shape of this signal is explained by the triplet quantum yield anisotropy brought about by the short lifetime of precursor radical pairs. The angular dependence of the anisotropy was evaluated. It was shown that the spectral shape of the triplet state of photosystem II reaction center observed in the case of singly-reduced primary quinone acceptor can also be described by the anisotropic quantum yield of the triplet, with practically the same angular dependence. These properties confirm the conclusions on the mechanism of photoinduced electron transfer in photosystem II, made in previous publications. The peculiarities in the functioning of photosystem II reaction centers are probably determined by strict limitations on the triplet state generation.

Occurrence of C(3) and C(4) photosynthesis in cotyledons and leaves of Salsola species (Chenopodiaceae).

Most species of the genus Salsola (Chenopodiaceae) that have been examined exhibit C(4) photosynthesis in leaves. Four Salsola species from Central Asia were investigated in this study to determine the structural and functional relationships in photosynthesis of cotyledons compared to leaves, using anatomical (Kranz versus non-Kranz anatomy, chloroplast ultrastructure) and biochemical (activities of photosynthetic enzymes of the C(3) and C(4) pathways, (14)C labeling of primary photosynthesis products and (13)C/(12)C carbon isotope fractionation) criteria. The species included S. paulsenii from section Salsola, S. richteri from section Coccosalsola, S. laricina from section Caroxylon, and S. gemmascens from section Malpigipila. The results show that all four species have a C(4) type of photosynthesis in leaves with a Salsoloid type Kranz anatomy, whereas both C(3) and C(4) types of photosynthesis were found in cotyledons. S. paulsenii and S. richteri have NADP- (NADP-ME) C(4) type biochemistry with Salsoloid Kranz anatomy in both leaves and cotyledons. In S. laricina, both cotyledons and leaves have NAD-malic enzyme (NAD-ME) C(4) type photosynthesis; however, while the leaves have Salsoloid type Kranz anatomy, cotyledons have Atriplicoid type Kranz anatomy. In S. gemmascens, cotyledons exhibit C(3) type photosynthesis, while leaves perform NAD-ME type photosynthesis. Since the four species studied belong to different Salsola sections, this suggests that differences in photosynthetic types of leaves and cotyledons may be used as a basis or studies of the origin and evolution of C(4) photosynthesis in the family Chenopodiaceae.

[The use of DNA polymerase from Thermus thermophilus]. / Primenenie DNK-polimerazy iz Thermus termophilus.

National DNA polymerase from Thermus thermophilus was used in polymerase chain reaction (PCR). The synthetic oligonucleotides (primers) to the basic structural HIV genes GAG, ENV, the genome DNA of donor peripheral blood lymphocytes were used, and the controls included the plasmid DNA with cloned HIV genome and the genome DNA of peripheral blood lymphocytes from HIV-infected persons confirmed by ELISA and Western blot analysis. The PCR technique and evaluation of the obtained results are described. The expediency of using PCR for different contingents is discussed.

[Reversibility of glycolysis in leaves of C4-plants]. / Issledovanie obratimosti glinkoliza v list' iakh C4-rastenii.

A conversion of the reaction of two cytoplasmic glycolysis enzymes, phosphoglycerate mutase and phosphopyruvate hydratase, is necessary for sucrose synthesis from pyruvate in leaves of C4-plants in the light, when phosphoenolpyruvate synthesis from pyruvate and phosphoglycerate reduction can be carried out by chloroplasts. Leaves of C4-plants differ from those of C3-plants in a higher activity of cytoplasmic glycolysis enzymes, which are distributed irregularly in two assimilatory tissues. The ratio of pyruvate kinase and enolase reaction activities is high in parenchyma linings of vascular fascicles (where mitochondria are concentrated), and it is low in mesophyl tissue, where phosphoglucerate in equilibrium phosphoenolpyruvate reaction is included into photosynthetic metabolism. The data obtained on isolated mesophyl protoplasts have shown that the reaction equilibrium is sharply shifted into the direction of phosphoenolpyruvate formation from phosphoglycerate. However, the incorporation of 14C into sugars is not completely inhibited in the atmosphere of N2-A possibility of incorporation of tri-carbon fragments into sugars in photosynthesizing leaves via conversion of enolase reaction and via alternative pathways is discussed.