ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05419.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—The efficiencies of the excitation–energy transfer from tyrosine to tryptophan residues in eight globular proteins in the native and denatured states are obtained by studying the wavelength dependence of the fluorescence quantum yield. The measurements are made over a wide wavelength range using a computer‐controlled spectrophotometer which can measure the fluorescence and absorbance simultaneously in one sample solution (Wadaet al., 1980). The values of the energy transfer efficiencies ranged from 0.17 ± 0.12 to 0.69 ± 0.06 in the native state and from ‐0.04 ± 0.09 to 0.12 ± 0.06 in the denatured state. These values are considerably lower than the values reported by Kronman and Holmes (1971); in particular, an almost complete absence of energy transfer for the denatured sta

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05420.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—Daunomycin and daunomycin–DNA complexes have been irradiated with UV light for up to 1 h. The drug was degraded to a variety of precipitates, all of which were devoid of the sugar moiety and these precipitates were further degraded by photobleaching. The precipitates have been fractionated by HPLC. The major component (resulting from 10min irradiation of a deoxygenated drug solution) was characterized by proton NMR and field desorption mass spectrometry as a modified aglycone (ring A was aromatic and was de‐acetylated). The production of hydrogen peroxide, photobleaching and the formation of precipitate were all inhibited by the addition of DNA. All of these effects appear to depend on the free drug concentration in solution. In the absence of DNA, all of these effects were enhanced by the presence of oxygen and diminished if the solutions were deoxygenated with

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05421.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract–Menaquinone‐8 (MQ‐8) was irradiatedin vivoinEscherichia coliB/r andin vitroafter extraction fromE. coliB/r, using monochromatic radiation in the range 313–578 nm. Within experimental error, the action spectra for loss of chromatographic mobility after irradiationin vivoandin vitroagree with each other and with the absorption spectrum of pure MQ‐8. The MQ‐8 is extremely sensitive to near‐UV light (300–380 nm), showing an F37in vivoat 334 nm of 1.3 kj/m2, a value 15 times lower than that required for growth delay, and 150 times lower than that for killing, ofE. coliB/r. The quantum yield for this reactionin vivoat 334 nm has the very high value of 0.26. The high sensitivity of MQ‐8 suggests involvement in near‐UV‐induced effects o

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05422.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—Cultured cells derived from a goldfish were irradiated with 254nm ultraviolet light. Cell survival and splitting of pyrimidine dimers after photoreactivation treatment with white fluorescent lamps were examined by colony forming ability and by a direct dimer assay, respectively. When UV‐irradiated (5 J/m2) cells were illuminated by photoreactivating light, cell survival was enhanced up to a factor of 9 (40min) followed by a decline after prolonged exposures. Exposure of UV‐irradiated (15 J/m2) cells to radiation from white fluorescent lamps reduced the amounts of thymine‐containing dimers in a photoreactivating fluence dependent manner, up to about 60% reduction at 120 min exposure. Keeping UV‐irradiated cells in the dark for up to 120min did not affect either cell survival or the amount of pyrimidine dimers in DNA, indicating that there were not detectable levels of a dark‐repair system in the cells under our conditions. Correlation between photoreactivation of colony forming ability and photoreactivation of the pyrimidine dimers was demonstrated, at least at relatively low fluences of photoreactiv

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05423.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—Survival curves were obtained for DNA repair‐deficient strains ofEscherichia coliK‐12 (polA1, uvrB5, andrecA56) exposed to near‐ultraviolet radiation [black light (BL)] in the presence of the DNA cross‐linking agent 8‐methoxypsoralen (8‐MOP) or in the presence of photosensitizers forming primarily monoadducts with DNA [angelicin; 3‐carbethoxypsoralen (3‐CPs); 5,7‐dimethoxycoumarin (DMC)], and after exposure to blue light (BluL) in the presence of 8‐MOP or 3‐CPs. An interpretation of these data suggests that DNA polymerase I is required for the major pathway of monoadduct repair, but appears to play little or no role in the repair of 8‐MOP cross‐links. TheuvrBandrecAstrains were very sensitive, both to the cross‐linking agent and to the monoadduct formers. The markedly different results for BL plus DMC or 3‐CPs compared to angelicin suggests that the DMC and 3‐CPs monoadducts are repaired by a different mechanism than are the angelicin monoadducts, or else DMC and 3‐CPs undergo photochemical side reactions that produce DNA lesions other than the expected monoadducts. From photochemical evidence, we predicted that fewer 8‐MOP monoadducts should be converted to cross‐links by BluL vs BL; this appears to be the case. 3‐CPs showed dramatically different biological results when irradiated with BL vs BluL, suggesting that 3‐CPs may form more types of photoproducts than the expected monoadducts; BluL, how

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05424.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—Mild photodynamic treatments of proflavine‐calf thymus DNA complexes induce a unique and quantitatively important alteration of the guanine residues which can be related to the lethal lesions due to the combined action of proflavine and light on phages. The ‘altered guanine’ is destroyed by HClO4but is recovered after partial DNA depurination under the form of two photoproducts. The first product, Gox, elutes as guanine on a Sephadex column but has a modified UV absorbance spectrum. It gives rise by further irradiation to another product, X, which elutes at pH 9.7 as a pyrimidine compound and presented a maximal UV absorbance at 246 nm. Product X is also selectively released by piperidine fixation onto the photo‐damaged DNA. The guanine degradation process is markedly decreased in the presence of the singlet oxygen quencher, NaN3. The photodynamic lesion inhibits the enzymatic degradation of the DNA but generates locally denatured regions that are sensitive to S1 end

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05425.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract–The techniques of viscoelastometry and S1 nuclease digestion were applied to the analysis of DNA damage in rat 9L cells treated with the combination of 8‐MOP (8‐methoxysporalen) and near‐UV light. Treatment of cells with near‐UV light alone resulted in a decrease in the viscoelastic retardation time under both denaturing and nondenaturing conditons. Exposure of cells to 8‐MOP alone yielded a maximum in the plot of retardation time vs dose under nondenaturing conditions, similar to that found with ionizing radition. This observation suggests that treatment with 8‐MOP alone leads to DNA strand breaks. Viscoelastic analysis of cell lysates under denaturing conditions demonstrated that treatment of cells with 8‐MOP and UV radiation led to substantial increases in both the viscoelastic retardation time and recoil, consistent with formation of DNA interstrand cross‐links. Viscoelastic analysis of cell lysates under nondenaturing conditions showed that exposure to long wavelength UV light in the presence of 8‐MOP produced a decrease in retardation time. This decrease reflects the combined effect of strand breaks and interstrand cross‐links. Results from the S1 nuclease assay confirmed these observations and permitted quantitation of DNA damage arising from single‐strand breaks and DNA interstrand crosslinks. The importance of including the effect of strand breaks in the quantitation of cross‐li

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05426.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—The irradiation of plant cells with UV radiation (254nm) causes various solutes to leak from the cells. Vesicles enriched in plasma membranes were prepared from wheat roots. These were used to determine whether UV radiation alters membrane function by direct action on the membranes and to distinguish between the chemical effects produced by high and low fluences of UV. The plasma membrane‐associated K+‐stimulated ATPase was very sensitive to UV radiation (100% inhibition with 1.35kJ/m2). ATPase activity measured in the absence of K+and K+‐stimulated ATPase activity measured in the presence of diethylstilbestrol were much less sensitive. Lipid breakdown, as measured by malondialdehyde production, occurred only at UV fluences greater than 1.

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05427.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY

摘要:

Abstract—Inactivation ofNeurospora crassaconidia from wild‐type and mutant strains by visible and near‐UV light has been investigated in the presence and absence of photosensitizing dyes. Inactivation by near‐UV is virtually unchanged by the presence of deuterium oxide or azide suggesting that, contrary to the situation with visible light and photosensitizing dyes,1O2is not involved in any substantial way in the formation of lethal lesions. The finding that carotenoid deficient strains are similar to wild‐type strains in sensitivity to near‐UV inactivation is consistent with1O2not being involved.Photodynamic inactivation of conidia by visible light occurs in the presence of methylene blue (MB), toluidine blue O (TB), or acridine orange (AO). Carotenoid deficient strains are more sensitive to such inactivation only when MB and TB are used. These results support the contention that MB and TB mediated damage involves the cell membrane where carotenoids are available for quenching, whereas AO mediated damage occurs in the nucleus sequestered from the protective influence of carotenoids.A newly isolated, lemon–yellow mutant, mapping to theal‐1 locus, exhibits sensitivities to photodynamic inactivation similar to other pure‐white mutants at the same locus. The sensitivity of this pigmented mutant is apparently related to insufficient unsaturation (seven to nine double bonds) of the two colored carotenoids, zeta–carotene and neurosporene, pro

ISSN:0031-8655    

DOI:10.1111/j.1751-1097.1981.tb05428.x

出版商:Blackwell Publishing Ltd    

年代:1981

数据来源: WILEY