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2.
E Cabrera-Juárez J K Setlow P A Swenson M J Peak 《Photochemistry and photobiology》1976,23(5):309-313
Abstract— The action spectrum for the oxygen-independent inactivation of native transforming DNA from Haemophilus influenzae with near-UV radiation revealed a shoulder beginning at 334 and extending to 460 nm. The presence of 0.2 M histidine during irradiation produced a small increase in inactivation at 254, 290 and 313 nm, a large increase at 334 nm and a decrease in inactivation at 365, 405 and 460 nm. Photoreactivation did not reverse the DNA damage produced at pH 7.0 at 334, 365, 405 and 460 nm, but did reactivate the DNA after irradiation at 254, 290 and 313 nm. The inactivation of DNA irradiated at 254, 290 and 313 nm was considerably greater when the transforming ability was assayed in an excision-defective mutant compared with the wild type, although DNA irradiated at 334, 365, 405 and 460 nm showed smaller differences. These results suggest that the oxygen-independent inactivation of H. influenzae DNA at pH 7 by irradiation at 334, 365, 405 and 460 nm is caused by lesions other than pyrimidine dimers. 相似文献
3.
LETHALITY IN REPAIR-PROFICIENT ESCHERICHIA COLI AFTER 365 nm ULTRAVIOLET LIGHT IRRADIATION IS DEPENDENT ON FLUENCE RATE 总被引:2,自引:0,他引:2
Abstract Reciprocity (total applied fluence produces the same response, regardless of the fiuence rate) for the lethal effects caused by 365 and 254 nm ultraviolet light (UV) was studied for repair-proficient and -deficient Escherichia coli strains. In the repair-proficient strain, E. coli WP2 uvrA * recA *, reciprocity after 365 nm UV was only observed at fluence rates of about 750 Wm-2 and above. Below this rate, the cells became increasingly sensitive as the fluence rate was decreased. Similar lack of reciprocity was obtained whether the cells were exposed at 0 or 25°C. The double repair-defective mutant, E. coli WP100 uvrA recA , showed complete reciprocity after 365 nm UV over the same range of fluence rates measured for the repair-proficient strain. For 254 nm UV, complete reciprocity occurred in both strains over a range of fluence rates differing by an order of magnitude. 相似文献
4.
Ultraviolet action spectra for DNA dimer induction, lethality, and mutagenesis in Escherichia coli with emphasis on the UVB region 总被引:4,自引:0,他引:4
Abstract —Ultraviolet (UV) action spectra were obtained for lethality and mutagenesis (reversion to tryptophan independence) in Escherichia coli WP2s for wavelengths 254–405 nm with detailed analysis in the UVB region (290–320 nm). Parallel chemical assay yields of pyrimidine dimers in DNA of E. coli RT4 were determined at the same wavelengths. Spectral regions isolated from a Xe arc and resonance lines from a high-pressure Hg-Xe arc lamp were both used for irradiation. In all cases, precise energy distributions throughout the isolated Xe bands regions were defined.
Lethality, mutagenesis, and dimer induction all decreased in efficiency in a similar fashion as the wavelengths of the radiation increased. Between 300 and 320 nm, all characteristics measured showed differences of about two and a half orders of magnitude. Between these wavelengths, the values of the three end points used either coincide with or parallel the absorption spectrum of DNA. The mutagenesis action spectrum coincides closely with the absorption spectrum of DNA. The lethality spectrum is closely parallel to the mutagenicity spectrum; the points, however, consistently occur at about 2 nm longer wavelengths. A calculation derived from the slope of the UVB spectra reveals that a 1-nm shift of the solar UV spectrum to shorter wavelengths would result in a 35% increase in its mutagenic potential. At 325 nm, both biological action spectra show sharp decreases in slope. In addition, above 325 nm the spectra for lethality. mutagenicity, and dimer formation diverge sharply; lethalities at these UVA wavelengths were approximately tenfold greater relative to mutagenicity than at shorter wavelengths. The relative yield of dimer formation by 365 nm radiation is intermediate between the yields for lethality and mutagenesis. 相似文献
Lethality, mutagenesis, and dimer induction all decreased in efficiency in a similar fashion as the wavelengths of the radiation increased. Between 300 and 320 nm, all characteristics measured showed differences of about two and a half orders of magnitude. Between these wavelengths, the values of the three end points used either coincide with or parallel the absorption spectrum of DNA. The mutagenesis action spectrum coincides closely with the absorption spectrum of DNA. The lethality spectrum is closely parallel to the mutagenicity spectrum; the points, however, consistently occur at about 2 nm longer wavelengths. A calculation derived from the slope of the UVB spectra reveals that a 1-nm shift of the solar UV spectrum to shorter wavelengths would result in a 35% increase in its mutagenic potential. At 325 nm, both biological action spectra show sharp decreases in slope. In addition, above 325 nm the spectra for lethality. mutagenicity, and dimer formation diverge sharply; lethalities at these UVA wavelengths were approximately tenfold greater relative to mutagenicity than at shorter wavelengths. The relative yield of dimer formation by 365 nm radiation is intermediate between the yields for lethality and mutagenesis. 相似文献
5.
OBSERVATIONS ON THE PHOTOSENSITIZED BREAKAGE OF DNA BY 2-THIOURACIL AND 334-nm ULTRAVIOLET RADIATION
Jennifer G. Peak Meyrick J. Peak Christopher S. Foote 《Photochemistry and photobiology》1986,44(2):111-116
Abstract— Breaks induced in purified DNA by 334-nm ultraviolet (UV) radiation are enhanced 30 times when 2-thiouracil (s2 Ura) is present during aerobic irradiation. This enhancement by s2 Ura is maximally effective at a concentration of about 1 m M. Anoxic irradiation reduces the s2 Ura-enhanced breakage by 90%, indicating a Type II photosensitization. Benzoate, glycerol, diazabicyclo[2.2.2.]octane (DABCO) and histidine all inhibit formation of s2 Ura photosensitized breaks, unlike diethylenetriaminepenta-acetic acid (DETAPAC) and catalase, which do not. The relationships between the concentration of DABCO. benzoate and histidine and their protection against induction of single strand breaks (SSBs) were similar, with little inhibition below 10 m M and maximal inhibition near 0.1 M for all compounds. Irradiation of the DNA-s2 Ura mixture dissolved in D2 O instead of H2 O enhanced the rate of induction of SSBs in DNA by 334-nm light almost five times. Addition of superoxide dismutase (40, 80 and 200 μg/ml) decreased the rate of induction of breaks in DNA by 334-nm radiation plus s2 Ura (in H2 O) by about 40%. Boiled superoxide dismutase had no effect. 相似文献
6.
Hydroxyl radical quenching agents protect against DNA breakage caused by both 365-nm UVA and by gamma radiation 总被引:2,自引:0,他引:2
The ability of hydroxyl radical (.OH) scavengers to reduce DNA breakage in isolated DNA from Bacillus subtilis by either gamma radiation or monochromatic radiation in the UVA region (365 nm) was examined by comparing dose reduction factors (the ratio of dose required to induce n DNA breaks in the absence to the presence of quencher). Previous data have demonstrated that acetate, formate, azide, and mannitol protect supercoiled DNA against gamma-radiation-induced ssb (single-strand breaks-relaxation of supercoil by first nick) in close agreement with the rate at which their solutions quench .OH. Here we show that these quenchers also protect against 365-nm-induced ssb. The ratios for protection against 365-nm induced DNA ssb in isolated B. subtilis DNA by the four quenchers are also in proportion to their ability to quench .OH. In view of the diverse chemical nature of the quenchers and the wide range of concentrations involved, these findings are evidence that both these radiations may induce ssb in DNA via a common step that might involve .OH. 相似文献
7.
EFFECTS OF INTENSITY AND FLUENCE UPON DNA SINGLE-STRAND BREAKS INDUCED BY EXCIMER LASER RADIATION 总被引:1,自引:0,他引:1
M. A. Chilbert M. J. Peak J. G. Peak M. J. Pellin D. M. Gruen G. A. Williams 《Photochemistry and photobiology》1988,47(4):523-525
Abstract— A Xenon-chloride excimer laser emitting energy at 308 nm was used to induce single-strand breaks (SSBs, frank breaks plus alkali-labile lesions as assayed by alkaline sucrose sedimentation techniques) in purified DNA from Bacillus subtilis . A fluence response study and a peak pulse intensity study were performed. At a pulse energy of 0.1 mJ/pulse, the radiation induced SSBs in a linear fashion (91 SSB/108 Da per MJ/m2 ) to a maximum exprimental fluence of 1.28 MJ/m2 . The pulse intensity study showed that there were no significant changes in DNA breakage (105 SSB/108 Da) between 2.93 times 109 and 5.86 times 1011 W/m2 (0.11 and 22.0 mJ/pulse) at a constant total fluence of 1.1 MJ/m2 (27000 mJ dose). This study has verified and extended previous work by quantifying the yield of SSBs induced in DNA by this laser radiation. 相似文献
8.
David Peak 《辐射效应与固体损伤》2013,168(1-2):309-321
Abstract Spatial correlations among reacting species in condensed media result from an interplay of reaction (which tends to lead to negative correlations), replacement or dissociation (which tend to produce positive correlations), and diffusion (which tends to smooth correlations out). Where correlations are high associative reactions are generally rapid. Where they are low the associative reaction is generally diminished. These characteristics of condensed phase processes have important consequences in a wide range of situations. In this paper, I review several examples drawn from radiation-physics, -chemistry, and -biochemistry of how spatial correlations determine the kinetics of reaction. Utilizing this theme, I also present two new results. I discuss a model of defect production in collision cascades in which the collective excitations during the cooling of the cascade contribute to defect recombination. A quantitative comparison with experiment is made. Lastly, I show how the kinetics of a diffusion-limited reversible reaction differ from a model which tacitly assumes that the spatial correlations which prevail are those of the irreversible reaction. A connection is drawn between these models and the observed kinetics of thermal donor formation. 相似文献
9.
Asha A. Oroskar Francis P. Gasparro Meyrick J. Peak 《Photochemistry and photobiology》1993,57(4):648-654
Abstract— An action spectrum of the relaxation of supercoied plasmid DNA(induction fo the firt single-strand break) by photoactivated 4'-aminomethyl-4, 5',8-trimethylpsoralen(AMT) has been determined using monochormatic UV photons from 254 to 405 nm. The spectrum of AMT-induced plasmid DNA relaxation fits closely with the absorbance spectrum of AMT in the spectral region between 313 nm and 405nm but deviates at wavelengths shorter than 313nm. This asay also reveals that the psoralen photosensitization reaction with DNA also produces piperidinelabile sites. Addition of mannitol and azide partially quenches the supercoil realaxation reaction, evidence for a role of Type II photosensitization pathway. 相似文献
10.
A widely used expression for the steady-state nucleation rate is determined, in part, by the concentration of critical nuclei in a constrained equilibrium state of the system under consideration. We show that when a dense solvent is present, the values of the constrained equilibrium concentrations reflect the spatial correlations that arise from reactant-solvent molecule collisions. We evaluate the effect of such correlations for a simple, model fluid in terms of measurable reaction rate constants; our analysis shows that correlations influence each step in the multistep process of cluster formation and that the overall impact on the nucleation rate is cumulative. We argue that the very low, homogeneous nucleation rates observed in certain miscibility gap experiments are easily understood in the context of our analysis.Supported in part by a grant from the Research Corporation of the Cottrell Foundation.John Simon Guggenheim Memorial Fellow. 相似文献