[Protection of Saccharomyces cerevisiae against oxidative and radiation-caused damage by alkyl hydroxybenzenes]. / Zashchita Saccharomyces cerevisiae alkiloksibenzolami ot okislitel'nogo i radiatsionnogo porazheniia.

The effects of C7-alkylhydroxybenzene (C7-AHB) and p-hydroxyethylphenol (tyrosol), chemical analogs of microbial anabiosis autoregulators, on the viability of yeast cells under oxidative stress were investigated. The stress was caused by reactive oxygen species (ROS) produced under gamma irradiation of cell suspensions using doses of 10-150 krad at an intensity of 194 rad/s or by singlet oxygen generated in cells photosensibilized with chlorin e6 (10 micrograms/l). C7-AHB was found to exert a protective effect. The addition of 0.05-0.16 vol% of C7-AHB to cell suspensions 30 min before irradiation protected yeast cells from gamma radiation (50 krad). The protective effect of C7-AHB manifested itself both in the preservation of cell viability during irradiation and in the recovery of their capacity to proliferate after irradiation. In our studies on photodynamic cell inactivation, the fact that the phenolic antioxidant C7-AHB protects cells from intracellular singlet oxygen was revealed for the first time. The analysis of difference absorption spectra of oxidized derivatives of C7-AHB demonstrated that the protective mechanism of C7-AHB involves the scavenging of ROS resulting from oxidative stress. The fact that tyrosol failed to perform a photoprotective function suggests that the antioxidant properties of microbial C7-AHB are not related to their chaperon functions. The results obtained make an important addition to the spectrum of known antioxidant and antistress effects of phenolic compounds.

[The role of labile complexes with oxygen in antioxidant activity of carotenoids]. / Rol' labil'nykh kompleksov s kislorodom v antioksidantnoi aktivnosti karotinoidov.

The present research work was done with the main purpose to study early stages of interaction of carotenoids (Car) with molecular oxygen and clarify their role in the mechanism responsible for Car radiochemical stability and carotenoid ability to decrease concentration of the most active oxygen transients like superoxide anion radicals (O2.-). Alcoholic and phosphate buffer (pH 7.5) solutions of carotenoid fucoxanthin (Fx) were used for investigation of the oxygen effect on the absorption spectra in the UV-Visible range. Special analysis of time dependent reversible shifts of absorption bands of evacuated Fx solution after contact with O2 indicated existence of equilibrium between two distinct forms of Car: Fx and the labile charge transfer complex (Fx+delta...O2-delta). The velocity of the achievement of equilibrium state and a degree of reversibility depend on chemical structure of the carotenoid, oxygen content and the solvent nature. Radiation-chemical methods were used to confirm the important role of primary Car oxocomplexes in different redox processes. It appeared that the yield of radiation-chemical bleaching of Fx, G-Fx, is 0.02-0.05 molecule/100 eV in the presence of oxygen, which in hundred times less the yield achieved in anaerobic conditions. The obtained results provide the evidence of Fx high level of stability under radiation, and demonstrate the supreme importance of reversible oxocomplex (Fx+delta...O2-delta) in stabilizing carotenoids in aerobic medium. The pulse radiolysis method with spectrophotometric registration of transients was used for generation and studying of mechanism O2.- interaction with different carotenoids. Introduction of any carotenoids containing oxygen (10(-5) M) in phosphate buffer solutions (pH 7.5) caused a red-shift of absorption maximum (from 5 to 15 nm) and difference in kinetics of O2.- decay. These results prove that radiation generated esolv- are directly accepted by (Car...O2) with consequent formation of superoxocomplexes (Car...O2.-) instead of O2.-. On the base of detecting the following transformation of superoxocomplexes the peroxocomplex (Car+...O2(2-)) was identified. In case of Fx a peroxocomplex (Fx+...O2(2-)) had absorption band with lambda max at approximately 360 nm. It is very important to mention that beta-carotene does not cause the similar effect and gets easily oxydized when exposed to the air.

[Immunological mechanisms of the radioprotective effects of ceruloplasmin]. / Immunologicheskie mekhanizmy radioprotektornogo deistviia tseruloplazma.

The aim of the work was to examine immunotropic features of celluroplasmine++ (Cp) and estimate its capacity as radioprotector. The pulse radiolysis method was used to set the mechanism of elementary reactions, which were responsible for antioxidant activity, and to demonstrate a particular role of reversible oxycomplexis, Cp...O2. Within in vitro test-systems the effects of Cp were examined on the model of interaction between lymphocytes from Shelter staff which constantly contacts with ionizing irradiation, and autologous erythrocytes in rosset-forming phenomenon (223 Shelter employees in comparison with 253 donors of Kyiv blood transfucion station). Expression of this Index in the presence of antigens with known poly-specificity was determined (antigens were taken from cortical and pyramid sections of kidney, liver, lungs, myocard, pancreatic gland, grey matter and aorta). Simultaneously the presence of analogous autoantibodies was determined (ELISA). It has been shown that Cp can reprogram the level of expression of immunovaluable receptors towards to norm. It has been also defined that Cp presence in blood irradiated in vitro (1-15 rem) promotes the masking of active centers of autoantibodies of different tissue specificity.

[The behavior of inulin in aqueous solutions under exposure to gamma radiation]. / Issledovanie povedeniia inulina v vodnykh rastvorakh pod vozdeistviem gamma-izlucheniia.

Radiochemical transformations of inulin in aqueous solutions, in air, in the presence of inert gases, helium, nitrogen, and in nitrous oxide exposed to various doses of 60Co gamma irradiation were investigated. It was shown that interactions of inulin with OH radicals are principally responsible for radiolytic decomposition of inulin. The data on radiolysis of more simple model systems were used to make available decomposition of absorption spectra of gamma-irradiated aerated aqueous solution of inulin.

The mechanism of interaction of ceruloplasmin with superoxide radicals.

1. The mechanism of interaction of CP with O2- radicals in chemical and enzymatic systems of superoxide radical generation as well as in the pulse radiolysis technique was studied. 2. It is found that CP does not exert any kinetic influence on the decomposition of superoxide radical and, unlike SOD, cannot catalyze the reaction of disproportionation of these radicals in systems with chemical and enzymatic generation of O2-. 3. The data obtained confirm the suggestion that CP interacts with precursors of O2- radicals. 4. The irradiation of CP does not change its inhibiting activity in the reaction of the formation of superoxide radicals in systems with enzymatic O2- generation, but decreases its oxidase activity. 5. The results obtained demonstrated that the increase in the radiation dose resulted in the decrease of the inhibiting activity of SOD, whereas the activity of CP did not change.

The mechanism of interaction of carnosine with superoxide radicals in water solutions.

The antiradical activity and the radiation stability of carnosine in water solutions was studied by the pulse radiolysis technique with spectrophotometric registration of absorbance. The transient spectra were recorded in the range 245-670 nm during 2 x 10(-6)-20 s after the pulse using a flow system for continuous change and saturation of the samples by different gases. Also, the spectra of the stable products of radiolysis were studied. The results obtained give evidence that carnosine in water solutions in the presence of oxygen behaves like a multifunctional antioxidant. Even at low concentrations, dipeptide forms a charge-transfer complex (Car ... O2-., lambda max = 265 nm) with the superoxide radical which changes the reactivity of O2-.. The absorbance band of the complex was shifted towards lower energy as compared to superoxide radical lambda max = 255 nm). The interaction of carnosine with OH-radicals proceeding at very high rate and resulting in the formation of a stable product suggested another type of dipeptide activity. The kinetic mechanism of the interaction of carnosine with products of radiolysis of water in aerobic conditions is discussed.

[Interactions of carnosine and superoxide radicals in aqueous solutions]. / Vzaimodeistvie karnozina s superoksidnymi radikalami v vodnykh rastvorov.

Carnosine was discovered to be able to interact with superoxide-anion and active hydroxyl radicals, using carnosine aqueous solutions. This interaction is specific and can be detected at carnosine concentrations more than 0.02 mM. Interaction of carnosine with O2 results in occurring of charge translocation complex with absorbtion maximum at 265 nm. Stability of this complex is dependent on the medium pH, decreasing with its acidification.