Synthesis and cytotoxic properties of anomeric 5-substituted 3'-azido-2',3'-dideoxyuridines]

Glycosylation of trimethylsilyl derivatives of 5-benzyloxymethyl- and 5-hydroxymethyluracil with 3-azido-2,3-dideoxy-5-O-benzoyl-D-ribofuranosyl chloride (prepared from ethyl 3-azido-2,3-dideoxy-5-O-benzoyl-D-ribofuranoside) and subsequent deacylation gave in both cases a mixture of anomeric 3'-azido-2',3'-dideoxy-5-benzyloxymethyl-or 5-hydroxymethyluridines. The anomers were separated by preparative TLC and their structures were studied by UV, IR and 1H-NMR spectroscopy. It is shown that 1-(3-azido-2,3-dideoxy-alpha-D-ribofuranosyl)-5-benzyloxymethyluracil has cytotoxic activity in vitro: in 10(-5)-10(-4) M concentrations it inhibits the thymidine incorporation into DNA of CaOv cells on 78.6-95.2%.     

Possible configuration of dimers of Gua-Cyt bases. Computation by molecular mechanic models and density functional theory

The energies of interactions between guanine and cytosine in various mutual positions were calculated by the methods of molecular mechanics with refined atom-atom potential functions and the quantum mechanics theory of density functional. Both methods indicate three types of mutual positions of bases in local energy minima. These types correspond to (1) nearly coplanar base positions with intermolecular hydrogen bond formation (base pairing); (2) arrangements of two bases in nearly parallel planes one above another (base stacking); and (3) nearly perpendicular positions of base planes. According to the calculations, the global energy minimum corresponds to the Watson-Crick base pair with three hydrogen bonds. A specific feature of the pair is a transition from many positions of type (2) to positions of type (1) without any energy barrier. This feature is revealed by both methods. Another special feature of this pair is a deviation, for most of mutual base positions, of the amine group atoms from the ring plane, the deviation being more pronounced for Gua. These features are important for understanding the conformational behavior of DNA fragments and the RNA structure.     

Identification of partially deuterated exometabolites during culture of tea fungi in heavy water

Exometabolites of tea fungus during the cultivation on heavy water were studied by methods of high-resolution proton and deuterium exchange. Is was shown that, depending on the degree of exchange of proton for deuterium in the methyl group of acetate, three isotopomers exist: -CH3, -CH2D, and -CHD2. Ethanol is represented by six isotopomers: -CHD-CH3, -CD2-CH3, -CD2-CH2D, -CD2-CHD2, -CHD-CH2D, and -CHD-CHD2. Relative concentration of these isotopomers and the percent content of deuterium were determined. Based on these data, the kinetics of metabolism of the object cultivated on heavy water was analyzed. It was show that the efficiency of glucose utilization is the same as during cultivation on light water with the exception that the time of utilization is significantly greater. At the same time, the parameters of utilization of ethanol and its conversion into acetic acid in the life activity of the tea fungus in heavy and light water are very similar.     

Karyogenomics of species of the genus Linum L

Using the molecular cytogenetic and RAPD methods of analysis, we studied genomes of 22 cultivated flax varieties and 24 wild species from six sections of the genus Linum L. The chromosome numbers were exactly determined in the karyotypes of all studied species, and all individual chromosomes were identified by the C/DAPI-banding pattern and localization of 26S rDNA and 5S rDNA. B chromosomes were identified and studied for the first time in species of the section Syllinum Griseb. According to the data obtained, the species studied were divided into eight groups on the basis of similarity of their karyotypes, which corresponded in general to their clustering based on the RAPD results. The systematic positions and phylogenetic relationships of the flax species were verified.     

Pathways of inclusion of isotopes 2H and 13C into exometabolites in course of glucose utilization by medusomycete]

The inclusion of 2H and 13C isotopes into the products of glucose utilization by medusomycete during its growth on deuterated media was studied by high-resolution NMR spectroscopy. Both unlabeled and 13C-labeled (in positions 1, 2, 6) glucose was used. It was shown that the glucose utilization proceeds by the classical Embden-Meyerhof-Parnas pathway. The incorporation of deuterium to the methyl group of ethanol can occur only during glucose-fructose-6-phosphate and phosphoenolpyruvate--pyruvate conversion. None of these stages by themselves is responsible for the existing distribution of deuterium atoms. The maximum inclusion of deuterium to the methyl group is no more than two atoms for the first glucose fragment (C1-C2-C3) and no more than one, for the second fragment (C4-C5-C6). The methylene group of ethanol is more accessible for deuterons because the proton surroundings of carbon atoms C2 and C5 completely changes. It was concluded that the maximum proton exchange occurs at positions C2 and C5; at positions C1, the proton exchange is lesser, and at position C6 it is the least. It was also shown that about 10% C1-C3 of triose leave the glycolysis cycle and are used in other processes.     

Identification of minor components of medusomycete exometabolites. 1H-NMR spectra in 13C and deuterium substitutions]

High-resolution 1H-NMR experiments were performed on 2H/13C isotopically labelled metabolites of growing medusomycete culture. Some minor metabolites were identified and the degree of their deuterization was established. Some of these metabolites were shown to be present in isomeric forms. Our results demonstrated that glycerol was produced in the growth medium on the early stage of the system adaptation to the growth in D2O.     

Biochemical characteristics of new thermosensitive secretory mutants of yeasts

New thermosensitive mutants of the yeast Saccharomyces cerevisiae which block the secretion of periplasmic enzymes at restriction temperature have been obtained. These mutants accumulate active low molecular weight and mature invertase species in the cell; the buoyant density of the cells in a Percoll gradient is higher than that in the wild strain cells. The mutant cells transferred to permissive temperature (25 degrees C) in the absence of protein synthesis can secrete some amount of accumulated invertase. It was found that the secretory defects of conditional mutants do not affect the activity of cytoplasmic enzymes (e.g., alcohol dehydrogenase) or the level of total protein synthesis and glycosylation and do not induce non-specific disturbances in energy metabolism and plasma membrane functions at restriction temperature. Some strains of new secretory mutants revealed uncoupled defective secretion of periplasmic enzymes and intrinsic membrane proteins (proline permease). The possibility of branching of the secretory pathway for periplasmic enzymes and cytoplasmic membrane proteins is discussed.     

9-(Adenylyl)alkylcobalamins as inhibitors of adenosylcobalamin-dependent glycerol dehydratase from Aerobacter aerogenes

The behavior of two coenzyme analogs, [(5-aden-9-yl)methoxyethyl] cob (III) alamin and [(5-aden-9-yl)pentyl] cob (III) alamin modified at the nucleoside ligand sugar moiety was studied in the system of adenosyl-cobalamin-dependent glycerol dehydratase from Aerobacter aerogenes. It was shown that neither of the analogs possesses coenzyme properties and that both are strong competitive inhibitors for adenosylcobalamin (AdoCbl). The affinity of the two analogs for the apoenzyme is higher than that of AdoCbl. The data obtained are indicative of the essential role of the ribofuranoside fragment of AdoCbl in the manifestation of the coenzyme activity. The apoenzyme interaction with the analogs under study is discussed in terms of the Dreiding stereomodels for AdoCbl and its analogs.     

Study of the combined action of an antibiotic and an immunostimulator using mathematical modeling

A mathematical model of antibiotic and immunostimulator (IMS) combined effect on various elements of the immune system and general state of patients with infectious diseases is described. The model was constructed as a system including 6 usual differential equations of the 1st order. With the use of this model and a computer many diverse variants of infection development under conditions of treatment with IMS at the background of antibiotic therapy were modeled. Ii was shown that IMS-antibiotic complexes markedly improved the indices of antibiotic therapy as compared to the use of the antibiotics alone. In combined use of IMS and antibiotics it was possible to lower the antibiotic doses without lowering the antimicrobial effect. The use of IMS at the optimal period led to balanced activation of the host specific and nonspecific resistance factors at the background of antibacterial therapy. The results of the mathematical modeling corresponded to the data on protective effect of salmozan (IMS) and doxycycline (antibiotic) combination in animals (albino mice). It was concluded that the described mathematical model was adequate for validation and optimization of schemes for combined use of IMS and antibacterial agents.