[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.

[Photodynamic damage of yeast subcellular fraction induced by elevated levels of endogenous protoporphyrin IX]. / Fotodinamicheskoe povrezhdenie subkletochnykh struktur drozhzhei s indutsirovannym nakopleniem éndogennogo protoporfirina IX.

The 2,2'-dipyridyl-induced accumulation of protoporphyrin IX in Saccharomyces cerevisiae cells was shown to be accompanied by the photoinhibition of cell respiration and the enhancement of the photoinduced permeability of plasma membranes to the fluorescent dye primuline. The visible-light illumination (at 400-600 nm) of the mitochondria and plasma membranes isolated from yeast cells with a high level of endogenous protoporphyrin IX intensified lipid peroxidation in these subcellular organelles. Comparative studies showed that the rad 52 mutant cells, which are deficient in the postreplicative recombinational DNA repair system, are considerably more sensitive to the inactivating action of visible light than are the wild-type cells and the rad 3 mutant cells, which are deficient in the excision DNA repair system. The contribution of photodynamic damage to the yeast subcellular organelles to the lethal photodynamic effect is discussed.

[Fluorescent photobleaching of endogenous protoporphyrin IX in yeast cells]. / Fotovytsvetanie fluorestsentsii éndogennogo protoporfirina IX v drozhzhevykh kletkakh.

Yeast Saccharomyces cerevisiae accumulate in the presence of chelator 2,2'-dipyridyl, two fractions of photosensitizer protoporphyrin IX, which fluoresce with maxima at 625 and 635 nm. The two fractions were found to differ from each other in the dynamics and character of fluorescence photobleaching. In contrast to the protoporphyrin IX that fluoresces with a maximum at 625 nm, the protoporphyrin IX fraction that fluoresces with a maximum at 635 nm is more photolable; in addition, upon photobleaching of its fluorescence, a new maximum at 675 nm appears.

[The photodynamic inactivation of Candida guilliermondii in the presence of photodithazine]. / Fotodinamicheskaia inaktivatsiia drozhzhei Candida guilliermondii v prisutstvii fotoditazina.

Photodithazine, a glucosamine salt of chlorin e6, enhanced the inactivation of Candida guilliermondii cells by visible light. The sensitizing effect of photodithazine was found to be related to free or cell surface-bound molecules of this dye. Sodium azide (a singlet oxygen quencher) and propyl gallate (an inhibitor of lipid peroxidation) protected yeast cells from the photodithazine-enhanced photoinactivation.

[Photoquenching of the bioluminescence of the genetically engineered Escherichia coli TG1 (pXen7) strain in the presence of photodithazine]. / Fotoindutsirovannoe podavlenie bioliuminestsentsii genno-inzhenernogo shtamma bakterii Escherichia coli TG1 (pXen7) v prisutstvii fotoditazina.

The photoquenching of the bioluminescence of the genetically engineered Escherichia coli TG1 (pXen7) strain was studied in the presence of the photosensitizer photodithazine, a glucosamine salt of chlorin e6. The photosensitized quenching of the bioluminescence was found to correlate with the colony-forming ability of the strain. The data obtained are discussed from the standpoint of using biosensor luminescent bacterial systems for the assessment of the efficiency of photosensitizers in antimicrobial photochemotherapy.

[Study of fluorescence from isolated yeast plasma membranes in visible range of the spectrum]. / Issledovanie fluorestsentsii izolirovannykh plazmaticheskikh membran drozhzhei v vidimoi oblasti spektra.

The fluorescence with maximum at 683 nm from isolated yeast plasma membranes has been detected. The fluorescence was due to a membrane-bound compound absorbing in the visible range of the spectrum. The fluorescence excitation spectrum of this compound has a structure typical for porphyrins. At the same time, in several fluorescence properties the porphyrin localized in the plasma membrane is different from other intracellular porphyrins (protoporphyrin, coproporphyrin).

[Stimulatory effect of serotonin on the growth of the yeast Candida guilliermondii and the bacterium Streptococcus faecalis]. / Stimuliruiushchee vliianie serotonina na rost drozhzhei Candida guilliermondii i bakterii Streptococcus faecalis.

Periodic addition of serotonin into a cultivation medium during growing of the yeast Candida guilliermondii and the bacterium Streptococcus faecalis exerts stimulatory influence on the growth of the cultures. The effect manifests itself in activating cell reproduction in the lag-phase, accelerating exponential growth of the cultures and their quicker reaching the stationary phase. The stimulatory effect of serotonin is optimal if serotonin is added to the growth medium at concentrations up to 10(-7) M with a periodicity of 2 hours.

[Competitive interaction of serotonin and the dye acridine orange with DNA]. / Konkurentnoe vzaimodeistvie serotonina i krasitelia akridinovogo oranzhevogo s DNK.

The interaction of serotonin and acridine orange dye with DNA isolated from bacterium Escherichia coli and the yeast Candida utilis has been analysed by spectrofluorimetric method. Using data on competitive binding to DNA of serotonin and acridine orange, known as DNA intercalator, a conclusion concerning the formation of intercalated complex between serotonin and DNA has been made. It is shown that for yeast DNA the constant of intercalated binding of serotonin is 3,5-fold smaller than for the bacterial one.

[Effect of serotonin on the yield of UV-induced thymine dimers in DNA]. / Vliianie serotonina na vykhod UF-indutsirovannykh timinovykh dimerov v DNK.

Using a fluorescence method the interaction between serotonin and DNA has been investigated and the association constant Kc = 4.2 X 10(4) M-1 was determined. Bound serotonin is shown to reduce the yield of UV-induced thymine dimers in DNA. It is calculated that the value of the effective distance over which each protector acts is a segment of the DNA helix about four base pairs long.

[Effect of the photo-induced synthesis of serotonin on the photoreactivation of Saccharomyces cerevisiae yeasts]. / O vliianii fotoindutsirovannogo sinteza serotonina na fotoreaktivatsiiu drozhzhei Saccharomyces cerevisiae.

The photoreactivation of yeast (Saccharomyces cerevisiae) cells irradiated by far-UV-light has been studied. It has been shown that the near-UV-induced (334, 365 nm) synthesis of serotonin in yeast is an underlying cause of its photoreactivation action spectrum change. The effect of serotonin is due to its binding to far-UV-irradiated DNA (pyrimidine dimers) making them unavailable to the photoreactivating enzyme. The data obtained support the idea that serotonin affects the repair enzymes which are engaged in an elimination of lethal photoproducts from DNA.

[Concurrent effect of ultraviolet rays of various wave lengths on Saccharomyces cerevisiae survival]. / Konkurentnoe deistvie ul'trafioletovykh luchei raznoi dliny volny na vyzhivaemost' Saccharomyces cerevisiae.

While studying the combined action of different UV wavelengths on Saccharomyces cerevisiae (strains XII and Cl-9), it has been found that preliminary irradiation with UV at 334 nm caused photoprotection of the cells against the lethal action of UV at 254 and 313 nm. Postradiation irradiation of strain XII incapable of photoreactivation with UV at 334 nm increased the lethal action of UV at 254 and 313 nm. The mechanisms of the both effects are based on serotonin synthesis induced by the light at 334 nm, as was shown using p-chlorophenylalanine, a specific inhibitor of serotonin synthesis. In strain CI-9 capable of photoreactivation, the postradiation effect of the light at 334 nm depends on the interaction of two different photobiological reactions induced by it, namely, photoreactivation and induced serotonin synthesis.