Biomedical subjects
Publications and source records attributed to V D Samuilov.
The treatment of sawdust with the fungus Panus tigrinus VKM F-3616 D changed the contents of functional groups in lignin from wood raw material. These changes are accompanied by the release of carboxyl and phenyl hydroxyl groups involved in chemical bond formation between wood particles in pressed materials manufactured from wood wastes.
Lignin consumption and synthesis of lignolytic enzymes by the fungus Panus (Lentinus) tigrinus cultivated on solid phase (modified and unmodified birch and pine sawdusts) were studied. The fungus grew better and consumed more readily the birch lignin than the pine wood. Peroxidase activity was higher in the case of pine sawdust; laccase and lignolytic activities, in the case of birth sawdust. Treatment with ammonia or sulfuric acid decreased lignin consumption by the fungus cultivated on either medium. Modification of sawdust by ultrasound increased lignin consumption and may be recommended for accelerating biodegradation of lignocellulose substrates.
Changes in the chemical composition of cotton plant stems used as a substrate for solid-phase cultivation of the fungus Panus tigrinus were studied as well as the effect of these changes on properties of the pressed materials made of these stems. During the first 3 days of growth, the fungus better consumed cellulose; then, the rate of cellulose consumption was comparable with that of lignin. Intensity and pattern of these changes depended on the age of inoculum. The rate of cotton plant waste biodegradation was higher when a 3-day-old incoculum was used. The pressed materials made of the raw stuff treated with a 3-day-old inoculum of P. tigrinus for 2-3 days displayed better characteristics. Annually, large amounts of lignocellulose stuff is lost while processing of agricultural waste: straw, awn, plant stems, etc. In the countries with developed cotton growing, the annual amount of only guza-paya (dry cotton plant stems) reaches several million tons. To solve this problem, bioconversion of these wastes is studied to manufacture useful products and materials.
The paper summarizes the results of HIV-1 serotyping by using 56 positive sera collected in the territory of the Republic of Tajikistan (RT) from intravenous drug users (IVDU). It was made by solid-phase ELISA based on synthetic peptides, mimicking different variants of the apical epitope of the HIV-1 gp120 V3-loop. Two types of conjugates, those specific to human IgG and IgA, were used to detect the immune complexes. Serotypes, as determined according to IgG and IgA-based ELISA, coincided, however, the latter were proven to be more suitable for serotyping. There is a high level of HIV-1 serotype heterogeneity among IVDU in RT; altogether, 4 serotypes were identified, i.e. B (10%), B+A/C (18%), A/C (20%) and A/C+B (52%). The modern serotype HIV-1 diversity in RT resembles the epidemiologic situation in the territory of the former USSR as observed in the late 80-ies-early 90-ies of the last century.
Lipid composition, intracellular products of lipid peroxidation (LPO), and the activities of extracellular enzymes were studied during submerged cultivation of the xylotrophic fungus Lentinus (Panus) tigrinus VKM F-3616D. The maximum secretion of ligninolytic enzymes during the phase of active mycelium growth correlated with increased content of readily oxidized phospholipids and unsaturated fatty acids and with low content of the LPO products. In the idiophase, which was characterized by lower excretion of extracellular ligninolytic enzymes, the content of more stable phospholipids, saturated fatty acids, and LPO products increased. A relationship between the composition of mycelial lipids and the secretion of ligninolytic enzymes was revealed.
The intermediate short-lived states arising in reaction centre preparations (RC) of purple bacterium Rhodospirillum rubrum are investigated under the conditions of low redox potential. Excitation by 353 and 530 nm laser pulses produced two states characterized by optical absorption changes in the range of 350--650 nm and lifetimes: 10--30 ns for the first state and 2.5 +/- 0.5 microseconds for the second one. The first state is similar to the state PF, described previously by Parson et al. for RC from Rps. sphaeroides. Carotenoid extraction with isooctane resulted in changing the spectrum with tau = 2.5 microseconds and in the appearance of new absorption changes similar to those for the R state observed before in carotenoidless bacterial strains within microsecond time range. The comparison of the microsecond spectra with difference spectra (continuous light minus dark) of RC from R. rubrum in the range of 350--650 nm made it possible to identify the states with tau = 2.5 microseconds as carotenoid triplet states. The ratio of quantum yields of PR and carotenoid triplet states production was determined as being 1 : 1. The conclusion was made that triplet-triplet energy transfer from state PR to carotenoid is responsible for the production of carotenoid triplet states.
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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.
A relative method in two modifications has been developed for determination of the quantum yield of primary photosynthesis energy conversion. The purple bacteria E. chaposhnikovii and Chr. minutissimum, R. rubrum chromatophores, cell extracts of E. shaposhnikovii, Rps. spheroides strains GA and R-26, pigment-protein complexes from green bacterium Chl. limicola and light subchloroplast particles, enriched in the photosystem I, were investigated. The quantum yields for all these objects were shown to be 90-98%. The accuracy of the relative method used is very high (within 2--4+). The photosynthetic units were proved to be of a multicentral type for all these systems. The quantum yield values permit estimation of the coefficient of efficiency of the primary conversion process as being approximately equal to 35-38% for bacteria and approximately equal to 50% plants.