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The MTT-assay is a colorimetric assay that measures the activity of enzymes that reduce MTT (a yellow tetrazolium bromide) in living cells. The MTT-test has been traditionally applied for the analysis of drug cytotoxicity in vitro. In our study MTT-assay was first applied for the investigation in vivo of the mechanisms of non-targeted effects of radiation and development of stress in multicellular crustaceans Daphnia magna. MTT test was based on the analysis of variation in the optical density of the irradiated Daphnia, which is proportional to the amount of formazan formed as a result of restoring MT with the help of dehydrogenases. So this indicator measures the effectiveness of the toxic effect of gamma-radiation. It describes the change in the balance of normal and damaged cells, suppression of the total dehydrogenase activity and other factors that are responsible for the metabolism of a multicellular organism. Daphnia were exposed to acute 60Co gamma-rays. According to our data, the effectiveness of toxicity was significantly raised in the two groups exposed to 100 and 1000 mGy of gamma-rays. Given the results of in vitro studies, our data therefore indicate that the compromised viability of irradiated Daphnia may be attributed to the cytotoxic effects within the dose-range of 100 and 1000 mGy. The results obtained in this study show that Daphnia represent a very useful experimental model, which allows a very efficient and quick analysis of many aspects of non-targeted effects of ionising radiation.

The data available in literature about formation, properties, possible biological role and practical application of the oxidized derivatives of B1 vitamin (thiamine) is first generalized and analysed in the review. It is known that at the values of pH > 7.0 the molecule of thiamine is able to undergo two-phase reaction of opening of thiazole ring with formation of anion of thiol form of thiamine and unstable tricyclic form. In the presence of oxidants in an alkaline environment a thiol form of thiamine is oxidized to thiamine disulfide, tricyclic form--to thiochrome. Oxidative transformation of thiamine molecule is promoted by phenoxyl radicals, their level can be substantially increased in animal tissues at oxidizing stress of different origin when the level of reactive forms of oxygen sharply increases and content of hemoproteins oxoferryl forms is raised. The analysis of literature data gives grounds to assume that thiamine and its hydrophobic metabolite--thiochrome--under certain conditions can perform an important antioxidant function in protection of cell structures against damaging action of peroxinitrite, nitrogen dioxide, peroxide. The presence of oxidized metabolites of thiamine and its phosphates in the cells of animals, even in minor quantities, is an established fact and, consequently, there is a possibility, that they can interact specifically with cellular structures or proteins to effect cellular processes in certain conditions.

A series of 12 compounds belonging to thiazoloindole derivatives possessing the antihypoxic activity were studied in order to reveal their actoprotective properties under usual and complicated (threatbahn running, exhaustive swimming) conditions in rats and mice. Five compounds were shown to protect animals from exhaustive loads in 1 h and 24 h after administration; four compounds produced the same effect under acute hypercapnic hypoxia conditions. In contrast, under the conditions of acute hemic hypoxia, all compound possessing high antihypoxic properties did not affect the physical endurance in rats and mice.

Benzthiazole dye thioflavin T (ThT) is widely used to study the formation and structure of amyloid fibrils. Nevertheless, till now there is no common opinion concerning molecular mechanisms of ThT binding to amyloid fibrils and the reasons of dramatic increase in its fluorescence quantum yield on incorporation into amyloid fibrils. Our data prove that ThT molecules incorporate in the amyloid fibrils in the monomeric form and there is no ground to suppose the formation of ThT dimers, eximers, or micells. It was shown that the increase in the quantum yield of ThT incorporated in amyloid fibrils was caused by restriction of benzthiazole and aminobenzene rings torsion fluctuations relative to each other. The use of equilibrium microdialysis allowed determining the absorption spectrum, the number of binding modes of ThT with insulin amyloid fibrils and for each mode determining the binding constants and the number of binding sites for each mode.

In this work the attempt to estimate a nitric oxide (NO*) role in regulation of the number of pool haemopoietic stem cells at the irradiated mice was made. With this purpose the number of new compounds from dihydrothiazine-thiazoline line was synthesized, their NO-inhibiting activity was investigated in vivo by the method of ESR-spectroscopy of spin trap and their influence on an output endogenous spleen colonies (CFU-S-8) after the total sublethal y-irradiation of mice in a doze of 6 Gy was also investigated. Was shown, that the tested compounds reduced the contents of NO* in a liver tissue of mice which have received an injection of nitric oxide synthesis inductor - lipopolysaccharide, and also increased an output CFU-S-8 forming endogenous colonies in the spleen of the irradiated mice. Received data testify to perceptivity of search radioprotective agents among NO* synthesis inhibitors.

It was shown that the thiazole derivative 3-decyloxycarbonylmethyl-4-methyl- 5-(2-hydroxyethyl)thiazole chloride (DMHT) (0.1 mM) reversibly reduced the transmembrane current in solutions of 10 mM CaCl2 and 100 mM KCl via ionic channels produced by alpha-latrotoxin from black widow spider (alpha-LT) and sea anemone toxin (RTX) in the bilayer lipid membranes (BLM). Introduction of DMHT from the cis-side of BLM inhibited transmembrane current by 31.6 +/- 3% and by 61.8 +/- 3% from the trans-side of BLM for alpha-LT channels. Application of DMHT to the cis-side BLM decreased the inward current through the RTX channels by 50 +/- 5%. Addition of Cd(2+) (0.1 mM) to the cis- or trans-side of a membrane after the DMHT induced depression of transmembrane current across the alpha-LT channels caused its further decrease by 85 +/- 5% that coincides completely with the intensity of Cd(2+)-inhibition in the control experiments without DMHT. These data suggest that DMHT may exert its inhibitory action on alpha-LT channels without considerable influence on the ionogenic groups inside the channel cavity. The comparative analysis of effective radii measured for alpha-LT and RTX channels on the cis- (0.9 nm and 0.55 nm, respectively) and the trans-side of BLM (< 0.467 nm for alpha-LT) allowed to propose the blocking action of DMHT for alpha-LT and RTX channels to result from direct penetration into the channel, achieved due to similar hydrodynamic size of blocking molecules and the size of toxin pores.

The influence of new non-natural regular minor groove binders (MGB), containing 2-4 imidazole, pyrrole or thiazole residues, and their conjugates with oligonucleotides, on the polymerization reaction catalyzed by HIV-1 reverse transcriptase was analyzed. Various model template-primer complexes: poly(A)-oligo(U), poly(A)-oligo(dT), poly(dA)-oligo(U), poly(dA)-oligo(dT) and activated DNA were used. The concentration of oligopeptides, giving 50% inhibition (I50) of the RT-dependent polymerization reaction, was shown to depend strongly on the structure of template-primer complexes, number and type of the heterocycle rings in the MGBs analyzed. The range of I50 for the most of the compounds studied is 7.7 x 10(-3)-1.0 x 10(-5) M. The affinity of MGB is minimal for poly(A)-oligo(U). However, some of imidazole and pyrrole-containing MGBs demonstrated unusually high affinity (I50 = 3 x 10(-9)-4 x 10(-8) M) to the above template-primer in complex with RT. The affinity of conjugates of thiazolecarboxamides with oligonucleotides complementary or partially complementary to the template, is 1-4 orders higher compared to free thiazolecarboxamides. The possible reasons of the dependence of I50 values upon the structure of the template-primer complexes, the structure of MGB, and their conjugates with oligonucleotides are discussed.

The antihypoxic activity of a series of 2-aminothiazole homologs and the related N-syccinamic acids was studied on four hypoxia models. All 2-aminothiazoles possess antihypoxant properties, which increase with the complexity of the molecular structure. The attachment of a succinic acid fragment at the amino group reduced toxicity, but also decreased the antihypoxant activity of drugs.

Derivatives of 2-amino-2-thiazoline exhibit muscarinomimetic properties in model experiments with isolated rat ileum. The activity of compounds strongly depends on the nature of substituents in 5-position of thiazoline ring. The most active spasmogenic compound is 5-iodomethyl-2-amino-2-thiazoline hydroiodide (EC50 = 13 +/- 2 microM). Its effect is very similar to activity of cholinergic agent pilocarpine (EC50 = 14 +/- 4 microM), but "intrinsic activity" parameter a (alpha = 0.87 +/- 0.12) of 5-iodomethyl-2-amino-2-thiazoline was more significant. Ileum contractions induced by this compounds were inhibited by atropine. Derivatives of 2-amino-2-thiazoline (like pilocarpine) were not demonstrated nicotinomimetic properties. These compounds demonstrate very weak anti-AChE activity. For 5-iodomethyl-2-amino-2-thiazoline hydroiodide the IC50 value is 0.39 +/- 0.09 mM.

A general survey of the poorly studied peptide antibiotics, microcins, which are produced by enterobacteria and effect gram-negative bacteria is conducted. In most cases, plasmid genes are responsible for microcin synthesis and the host cell immunity to the produced microcin. A complex system of plasmid and chromosomal genes is involved in the production and immunity to microcins. The chemical structure of three studied microcins is unusual. It was shown that peptides of the microcin molecules are synthesized on ribosomes and often modified posttranslationally. New types of posttranslational modifications were revealed in the biosynthesis of the microcin B17. These modifications are related to the formation of the thiazole and oxazole rings in its molecule; plasmid genes are responsible for these modifications. It was demonstrated that the smallest gene (21 bp) of all known genes controls the synthesis of the heptapeptide contained in the microcins of the C type.

The DNA complexes with actinocyl-bis-bithiazole have been investigated by spectrophotometry, viscometry and flow birefringence. It was estimated, that at low degrees of binding (r < or = 0.07) this compound binds to DNA by bisintercalation via bithiazole groups located in positions 1 and 9 of the phenoxazone chromophore. The phenoxazone moiety plays in this case the role of a link connecting two intercalating fragments. As r increases, external groove binding becomes the second type of complex formation.

The method of potential functions was used to predict adequately the radioprotective efficacy of thiazole derivative series, the geometrical indexes (1n A2 and A6) and anti-ion mass being applied as descriptors for organic and inorganic molecule parts respectively.

The chromophore moiety of the copsomycin molecule was isolated in the form of dimethyl ether as an individual substance from the products of antibiotic acid hydrolysis. Physicochemical properties of the chromophore were studied. UV, 1H and 13C NMR, mass spectrometry and elementary analysis showed that the copsomycin molecule moiety was identical to the chromophore moiety of the molecule of multiomycin or nosiheptide.