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1.
The involvement of reactive oxygen species (ROS) in the induction of DNA damage to Escherichia coli cells caused by UVC (254 nm) irradiation was studied. We verified the expression of the soxS gene induced by UVC (254 nm) and its inhibition by sodium azide, a singlet oxygen (1O2) scavenger. Additional results showed that a water-soluble carotenoid (norbixin) protects against the lethal effects of UVC. These results suggest that UVC radiation can also cause ROS-mediated lethality. 相似文献
2.
Bacterial cells of the strain Escherichia coli K12 were exposed to millimeter electromagnetic waves (mm waves) with and without additional exposure to ultraviolet light λ = 254 nm (UVC). The mm waves were produced by a medical microwave generator emitting a 4-GHz-wide band around a 61 GHz center frequency and delivering an irradiation of 1 mW/cm 2 and a standard absorption rate (SAR) of 84 W/kg to the bacteria. Exposure to the mm waves alone for up to 30 minutes did not change the survival rate of bacteria. Exposure to mm waves followed by UVC irradiation also did not alter the number of surviving E. coli cells in comparison to UVC-treated controls. When mm waves were applied after the UVC exposure, a dose-dependent increase of up to 30% in the survival of E. coli was observed compared to UVC + sham-irradiated bacteria. Because sham controls and experimental samples were maintained under the same thermal conditions, the effect is not likely to be due to heating, although the possibility of nonuniform distribution of microwave heating in different layers of irradiated bacterial suspension cannot be ruled out. The mechanism for this effect appears to involve certain DNA repair systems that act as cellular targets for mm waves. © 1995 Wiley-Liss, Inc. 相似文献
3.
Summary Solar ultraviolet radiation has been associated with the induction of skin cancer. Recent studies have indicated that near-ultraviolet, especially UVB, is mutagenic. Exposure to trivalent inorganic arsenic compounds has also been associated with increased skin cancer prevalence. Trivalent arsenic compounds are not mutagenic per se, but are comutagenic with a number of cancer agents. Here, we test the hypothesis that arsenite enhances skin cancer via its comutagenic action with solar ultraviolet radiation. Irradiation of Chinese hamster V79 cells with UVA (360 nm), UVB (310 nm) and UVC (254 nm) caused a fluence-dependent increase in mutations at the hprt locus. On an energy basis, UVC was the most mutagenic and UVA the least. However, when expressed as a function of toxicity, UVB was more mutagenic than UVC. Nontoxic concentrations of arsenite increased the toxicity of UVA, UVB and UVC. Arsenite acted as a comutagen at the three wavelengths; however, higher concentrations of arsenite were required to produce a significant ( P < 0.05) comutagenic response with UVB. The increased mutagenicity of UVB and UVA by arsenite may play a role in arsenite-related skin cancers. 相似文献
4.
In order to investigate the feasibility of using ultraviolet (UV) irradiation to prevent the invasive Asian mussel, Limnoperna fortunei, from colonizing components of the cooling systems of industrial and power plants, the mobility and mortality of its larvae were assessed after exposure to different doses of UVC (λ = 254 nm) in laboratory conditions. Total (100%) mortality was achieved with a dose of 149 mJ cm ?2 at 23?°C and 103 mJ cm ?2 at 25.8?°C. Immediately after exposure, larvae were alive but had reduced mobility. The proportion of active larvae increased after 24 h, but fell again at 48 and 72 h to levels similar to those immediately after exposure. The highest mortality rates were always recorded at the last observation, 72 h after exposure. These results indicate that the larvae of L. fortunei are highly sensitive to UVC, suggesting that UV irradiation has the potential to control fouling by this mussel when the water is relatively clear. However, application of UV-based technologies in plants that use cooling water from water bodies with high loads of suspended solids (eg the Paraná-Uruguay basin, with ca 160 mg l ?1 of suspended solids and absorbance values around 0.255) is unlikely to be effective without prior filtration of the water. 相似文献
5.
A high-pressure liquid chromatography (HPLC) technique, previously developed for nitrite (NO −2) and nitrate (NO −3) measurements [3], was used to measure chlorite (ClO −2) production by Nitrobacter winogradskyi. The determination of ClO −2 by HPLC involves monitoring the column effluent with a UV detector at 214 or 254 nm. Although the absorbance of ClO −2 at 214 nm was about 5 times greater than at 254 nm, interference from other compounds in the culture filtrates of N. winogradskyi contributed to an unstable detector signal. The detection limit at 254 nm for ClO −2 in deionized water was about 1 μM.The measurement of ClO −2 in N. winogradskyi culture filtrates was done with detection at 254 nm. The maximum concentration of ClO −2 produced by anaerobically incubated cell suspensions of N. winogradskyi was about 80 μM. 相似文献
6.
It has been shown that direct excitation of NADH (or NADPH) in aqueous medium at 254 nm, or at wavelengths longer than 320 nm (where only the reduced nicotinamide moiety absorbs), leads to generation of NAD + (or NADP +). The reaction proceeds both in the presence and absence of oxygen. Under aerobic conditions the reaction is accompanied by formation of H 2O 2 at a level equimolar with that of the NADH present in solution. On irradiation at wavelengths longer than 320 nm, conversion of NADH to enzymatically active NAD + is about 75%. Under analogous irradiation conditions, the dimers (NAD) 2 and (NADP) 2 undergo disproportionation to NAD + and NADP +, respectively, to the extent of 90%. Both physicochemical and enzymatic criteria were employed to formulate mechanisms for the photooxidation of NADH and the photodisproportionation of the dimer (NAD) 2. 相似文献
7.
UVC light is a widely used sterilization technology. However, UV lamps have several limitations, including low activity at refrigeration temperatures, a long warm-up time, and risk of mercury exposure. UV-type lamps only emit light at 254 nm, so as an alternative, UV light-emitting diodes (UV-LEDs) which can produce the desired wavelengths have been developed. In this study, we validated the inactivation efficacy of UV-LEDs by wavelength and compared the results to those of conventional UV lamps. Selective media inoculated with Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes were irradiated using UV-LEDs at 266, 270, 275, and 279 nm in the UVC spectrum at 0.1, 0.2, 0.5, and 0.7 mJ/cm 2, respectively. The radiation intensity of the UV-LEDs was about 4 μW/cm 2, and UV lamps were covered with polypropylene films to adjust the light intensity similar to those of UV-LEDs. In addition, we applied UV-LED to sliced cheese at doses of 1, 2, and 3 mJ/cm 2. Our results showed that inactivation rates after UV-LED treatment were significantly different ( P < 0.05) from those of UV lamps at a similar intensity. On microbiological media, UV-LED treatments at 266 and 270 nm showed significantly different ( P < 0.05) inactivation effects than other wavelength modules. For sliced cheeses, 4- to 5-log reductions occurred after treatment at 3 mJ/cm 2 for all three pathogens, with negligible generation of injured cells. 相似文献
8.
Aims: To (i) evaluate the UV radiation in the ‘C’ band/high efficient particulate air (UVC/HEPA) instrument’s potential to inactivate spores of Bacillus atrophaeus and selected Bacillus species and (ii) test whether a titanium dioxide coating inside the cylindrical HEPA filter improves the system's efficacy. Methods and Results: Known amounts of dried spore preparations of B. atrophaeus, Bacillus cereus, Bacillus megaterium, Bacillus stearothermophilus and Bacillus thuringiensis were exposed to the UVC lamp within a cylindrical HEPA filter for different time lengths (30 min to 48 h) and with different air flow speeds (0–235 l s ?1). The log 10 reduction (range 5–16 logs) of colony forming units for spores exposed to the UVC compared with the unexposed spores was significant ( P < 0·0001). The addition of a titanium dioxide (TiO 2) veneer to the interior surface of the HEPA filter significantly increased the inactivation of spores ( P < 0·0001). Conclusions: The UVC/HEPA unit could inactivate spores of B. atrophaeus, B. cereus, B. megaterium, B. stearothermophilus and B. thuringiensis. Significance and Impact of the Study: The UVC/HEPA unit represents an effective method of decontaminating circulating air within an air‐duct system as found in a building. 相似文献
9.
Spore-forming microbes recovered from spacecraft surfaces and assembly facilities were exposed to simulated Martian UV irradiation. The effects of UVA (315 to 400 nm), UVA+B (280 to 400 nm), and the full UV spectrum (200 to 400 nm) on the survival of microorganisms were studied at UV intensities expected to strike the surfaces of Mars. Microbial species isolated from the surfaces of several spacecraft, including Mars Odyssey, X-2000 (avionics), and the International Space Station, and their assembly facilities were identified using 16S rRNA gene sequencing. Forty-three Bacillus spore lines were screened, and 19 isolates showed resistance to UVC irradiation (200 to 280 nm) after exposure to 1,000 J m −2 of UVC irradiation at 254 nm using a low-pressure mercury lamp. Spores of Bacillus species isolated from spacecraft-associated surfaces were more resistant than a standard dosimetric strain, Bacillus subtilis 168. In addition, the exposure time required for UVA+B irradiation to reduce the viable spore numbers by 90% was 35-fold longer than the exposure time required for the full UV spectrum to do this, confirming that UVC is the primary biocidal bandwidth. Among the Bacillus species tested, spores of a Bacillus pumilus strain showed the greatest resistance to all three UV bandwidths, as well as the total spectrum. The resistance to simulated Mars UV irradiation was strain specific; B. pumilus SAFR-032 exhibited greater resistance than all other strains tested. The isolation of organisms like B. pumilus SAFR-032 and the greater survival of this organism (sixfold) than of the standard dosimetric strains should be considered when the sanitation capabilities of UV irradiation are determined. 相似文献
10.
Exposing Pseudomonas aeruginosa biofilm grown on the inner surface of Teflon and silicone tubes to UVC light (265 nm) from light emitting diodes (LED) has previously been shown to substantially reduce biofilm growth. Smaller UVC fluencies were required to disinfect Teflon tubes compared to silicone tubes. Light propagation enhancement in tubes can be obtained if the refractive index of the intra-luminal saline solution is higher than that of the polymer. This condition is achieved by using Teflon tubes with a low refractive index (1.34) instead of the polymers with a high refractive index (1.40–1.50) normally used for tubing in catheter production. Determining whether or not UVC light exposure can disinfect and maintain the intra-luminal number of colony forming units (CFUs) at an exceedingly low level and thus avoid the growth and establishment of biofilm is of interest. The use of UVC diodes is demonstrated to be a preventative disinfection treatment on tubes made of Teflon, which enhances the UVC light propagation, and on tubes made of a softer material, ethylene vinyl acetate (EVA), which is suitable for catheters but much less suitable for UVC light propagation. Simulating an aseptic breach (~10 3–10 4 CFU ml ?1), the UVC disinfection set-up was demonstrated using tubes contaminated with planktonic P. aeruginosa. After the tubes (10–20 cm) were inoculated with the bacterial solution for 3 h, they were emptied and filled with saline solutions (0.9–20%). Next UVC fluencies (0–21 mJ cm ?2) were applied to the tubes 3 h after inoculation. Colony counts were carried out on liquid samples drawn from the tubes the first day after UVC treatment and liquid and surface samples were collected and analyzed 3–4 days later. A fluence of approximately 1.0 mJ cm ?2 was noted as being sufficient for no growth for a period of 3–4 days for the Teflon tubes. Determining the fluence threshold for the EVA tubes was not possible. Almost all of the UVC-treated EVA tubes were disinfected simply by filling the tubes with a saline solution. Direct UVC treatment of the contaminated EVA tubes revealed, however, that a fluence of 21 mJ cm ?2 killed the bacteria present in the tubes and kept them disinfected for a period of 3–4 days. 相似文献
11.
Summary Isolated lipids from Deinococcus radiodurans were reconstituted at final concentrations of 1 mg/ml into dioleoyl phosphatidyl choline (DOPC) vesicles and assayed for the ability to protect cells of Escherichia coli against killing by UV light (254 nm). Values of D 37 (UV dose required to reduce the number of surviving cells to 37% of the original number) were calculated from killing curves. E. coli was afforded the greatest protection with an individual lipid, identified as vitamin MK8 (D 37=310 J//m 2, compared to D 37=67 J/m 2 for E. coli irradiated in the presence of DOPC alone). Liposome-mediated protection was dependent on UV 254 absorbance and not on turbidity-related light-scattering. BOth vitamin MK8 from D. radiodurans and vitamin K 1, which is available commercially, showed a similar degree of UV 254-protection for E. coli. The UV-protective properties of vitamin K 1 were also investigated on mammalian cells in comparison with other natural lipids and known sunscreens. Survival curves were obtained for mouse fibroblast (L) cells irradiated at UV 254 in the absence or presence of DOPC liposomes into which were incorporated various natural lipids or standard sunscreen ingredients, all at final concentrations of 1 mg/ml. Experimentally determined values of D 37 were as follows: Vitamin K 1, 73 J/m 2; \-carotene, 44 J/m 2; -tocopherol, 20 J/m 2; sulisobenzone, 156 J/m 2; p-aminobenzoic acid (PABA), 113 J/m 2; benzophenone, 80 J/m 2; oxybenzone, 61 J/m 2 and DOPC alone. 23 J/m 2. Vitamin K 1, the most protective lipid tested, was also compared with PABA and oxybenzone (all at concentrations of 20 mg/ml; applied topicall) for its ability to protec Skh-hairless mice from UV 254-induced erythema, yielding a UV 254 protection factor of 3.5. In addition, vitamin K 1 (at 100 mg/ml) was able to provide hairless mice with a small degree of UVB protection, as indicated by an experimentally determined Solar Protection Factor of 1.5–2.0. Although it is concluded that vitamin K is not likely to account for the extraordinarily high degree of UV-resistance of D. radiodurans, vitamin K does show characteristics worthy of its consideration as a UV-screening agent.
Offprint requests to: R. Anderson 相似文献
12.
The reactions between superoxide free radical anion (.O −2) with the halocarbons CCl 4, CHCl 3, BrCH 2CH 2Br(EDB), decachloro-biphenyl (DCBP), and 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) in dimethyl sulphoxide (DMSO) results in the emission of chemiluminescence (CL). The chemiluminescence reactions are characterized as having biphasic second order kinetics, CL wavelengths between 350 nm and 650 nm, and exhibiting perturbation by chemicals reactive with singlet oxygen. These data suggest that singlet oxygen species are the excited state responsible for the light emissions. Polarographic studies confirm .O −2 consumption and halide release in the reactions, while gas liquid chromatography and NBT reduction demonstrate the decomposition of the halocarbons into products. A chemiluminescent reaction mechanism is proposed involving reductive dehalogenation of the halocarbons and the generation of singlet oxygen. The significance of singlet oxygen generation is discussed with respect to a general mechanism for explaining the rapid initiation of lipid peroxidative membrane damage in halocarbon toxigenicity in animal and plant tissues. 相似文献
13.
Production of NO and N 2 O by the heterotrophic nitrifier Alcaligenes faecalis subsp. parafaecalis was studied during growth in batch and continuous culture on peptone-meat extract medium. Depending on oxygen saturation level, medium redox status and amount of substrate supplied, the microorganisms produced 0.002–0.25 mg NO-N h - 1 (g protein) - 1 and 0.16–2.4 mg N 2 O-N h - 1 (g protein) - 1 . Maximum rates of nitrogen oxides production were observed during peak events initiated by sudden changes of oxygen supply in the medium and were due to combined nitrification/denitrification taking place simultaneously within the cells. Based on model simulations of enzymatic kinetics of denitrification, possible mechanisms of increased nitrogen oxides production during periods of changes in oxygen supply are suggested. 相似文献
14.
Ultraviolet (UV) light irradiation has serious consequences for cell survival, including DNA damage by formation of cyclobutane pyrimidine dimers (CPD) and pyrimidine (6,4) pyrimidone photoproducts. In general, the Nucleotide Excision Repair pathway repairs these lesions; however, all living forms, except placental mammals and some marsupials, produce a flavoprotein known as photolyase that directly reverses these lesions. The aim of this work was the isolation and identification of Antarctic UVC-resistant bacteria, and the search for novel photolyases. Two Antarctic water samples were UVC-irradiated (254 nm; 50–200 J m− 2) and 12 UVC-resistant bacteria were isolated and identified by 16S rDNA amplification/analysis as members of the genera Pseudomonas, Janthinobacterium, Flavobacterium, Hymenobacter and Sphingomonas. The UVC 50% lethal dose and the photo-repair ability of isolates were analyzed. The occurrence of photolyase coding sequences in Pseudomonas, Hymenobacter and Sphingomonas isolates were searched by PCR or by searching in the draft DNA genome. Results suggest that Pseudomonas and Hymenobacter isolates produce CDP-photolyases, and Sphingomonas produces two CPD-photolyases and a 6,4-photolyase. Results suggest that the Antarctic environment is an important source of genetic material for the identification of novel photolyase genes with potential biotechnological applications. 相似文献
15.
We compared the protective effect of three polymers; starch, gelatin and sodium alginate (2, 3, 5%) as coating materials, on the stability of microencapsulated formulation of Bacillus thuringiensis after exposure to Ultra Violet (UV) R. Microencapsulated Spore Crystal Aggregate (SCA) formulations were prepared by the emulsion gelling method. The protective effect of polymers was evaluated by measuring spore viability. Bioassay and release tests were done on the microencapsulated formulations. Sodium alginate (5% w/w) showed the highest viabilities of 90 and 86% after exposure to Ultra Violet in long term (UVB 385 nm) and Ultra Violet in short term (UVC 254 nm) radiation, respectively, while viabilities of non-microencapsulated spores under these conditions were 40 and 50%, respectively. The crystal activity (mortality) of irradiated and non-irradiated free spore formulations on second-instar larvae of Ephestia kuehniella were 15 and 93%. However, the mortalities caused by irradiated and non-irradiated microencapsulated formulations were 70 and 80% on the 10th day of the experiment. The size range of the microcapsules was 7–20 µm while the microcapsulation efficiency was 86%. The release behaviour of microspheres conformed best to Korsmeyer–Peppas semi-empirical model with the correlation of R2 = 0.98. 相似文献
16.
Ullucus virus C (UVC) is a comovirus prevalent in Ullucus tuberosus grown at high altitudes in the Bolivian and Peruvian Andes. It was transmitted mechanically to U. tuberosus (Basellaceae) and to five of 26 species from three of eight other families, infecting U. tuberosus symptomlessly but inducing conspicuous systemic infection in Chenopodium amaranticolor and C. quinoa. Sap from infected C. quinoa was usually infective after 10 min at 70 but not 75 °C, after dilution to 10 -7 but not 10 -8, and after 8 but not 16 wk at 20 °C. UVC was not transmitted by either of two aphid species ( Aphis gossypii and Myzus persicae) or through seed of C. quinoa, but it was transmitted by leaf contact between infected and healthy plants. UVC has isometric particles which, in neutral phosphotungstate, are c. 28 nm in diameter. The particles sediment as three components (T, M and B) with sedimentation coefficients ( s?20, w) of 51 S (T), 95 S (M) and 116 S (B). M component particles have a buoyant density (g cm -3) in caesium chloride of 1.404, and B component particles separated into minor and major sub-components with densities of 1.409 and 1.463, respectively. T, M and B particles were serologically indistinguishable, and each contained similar relative amounts of two polypeptides of mol. wts 20 700 and 45 100. T particles contained only protein, but M particles also contained c. 30% ss-RNA of mol. wt 1–45 ×10 6 and B particles c. 38% ss-RNA of mol. wt 2·2 × 10 6. The virus is serologically distantly related to cowpea mosaic virus but, as it showed no relationship to any of 11 other similar viruses, it is probably a distinct member of the comovirus group. 相似文献
17.
Mutations to ouabain resistance (selecting for base modifications at the co-dominant Na+K+-dependent ATP-ase locus) and thioguanine resistance (selecting for a wide range of genetic changes at the recessive hypoxanthine-guanine phosphoribosyl transferase locus) were measured in a repair-proficient human lymphoblastoid line with defined monochromatic radiations in the UVC (254 nm), UVB (302 nm, 313 nm), UVA (334 nm, 365 nm) and visible (405 nm) ranges. No mutations were detected at wavelengths in the range 334-405 nm. At 254 nm and 313 nm, both mutations to thioguanine resistance and survival were consistent with those expected from the relative levels of cyclobutane-type pyrimidine dimers induced. However, at 313 nm, the ratio of ouabain-resistant to thioguanine-resistant mutants is 10 times higher than at 254 nm, indicating that a unique type of pre-mutagenic base damage is induced at the longer wavelength. Radiation in the UVA (334 nm) range reduced the induction of mutations by a UVC (254 nm) wavelength at both mutation markers. These results suggest, first, that distinct types of biologically expressed genetic damage may be induced in the UVB region of sunlight and, second, that strong interactions may occur between the different wavelength regions of sunlight that can modify the expression of this genetic damage in human cells. 相似文献
18.
Three pairs of E. coli strains with different dark-repair potentials, viz. H/r30 and H/r30-R, H s30 H s30-R, CSR 603 and AB 2480, have been investigated for their survival after exposure to 254-nm and 365-nm radiation. Each pair consists of a non-photorepairable ( phr?) and a photorepairable ( phr+) strain of otherwise identical or similar genotype. At 254 nm, the mean inactivation fluence ( F0.37) is for the dark-repair proficient phr? strain (H/r30) 300–750 times greater than for the completely dark-repair deficient phrtt- strain (CSR 603), but at 365 nm the F0.37's differ by a factor of only 5–10. Comparison of survival curves of phr? and phr+ strains indicates that, at all three levels of dark-repair potential, lethal damage resulting from 365-nm exposure is extensively photorepaired by the same wavelength. Qualitatively similar effects were observed with sunlight from which all wavelengths < 360 nm were filtered out. Furthermore, we have shown that fluences of 365-nm radiation used in our experiments do not damage the enzymatic dark-repair systems themselves. These results seem compatible with one another only if one assumes that photoenzymatic repair is capable of abolishing lethal DNA damage other than the common types of cyclobutane dipyrimidines occurring after 254-nm irradiation. 相似文献
19.
Two novel palladium(II) complexes with a thiosalicylic acid (HSC 6H 4CO 2H) ligand, with the formulas [Pd(TSA)(L)]· mH 2O (TSA is thiosalicylic acid; in complex 1, L is 1,10-phenanthroline and m = 1; in complex 2, L is 2,2′-bipyridine and m = 2), have been synthesized and characterized. The coordination geometry of both palladium atoms is square planar; they are
four-coordinated and each is coordinated in an N,N,O −,S − mode. There is a sigmoid oxygen chain in complex 1, but an oxygen ring in complex 2. The competitive binding of the complexes to HeLa cell DNA (HL-DNA) has been investigated by fluorescence spectroscopy. The
results show that the two complexes have the ability to bind with HL-DNA. Viscosity studies suggest that the complexes bind
to DNA by intercalation. Gel electrophoresis assay demonstrated the ability of the complexes to cleave the HL-DNA. The two
complexes exhibit cytotoxic specificity and a significant cancer cell inhibitory rate. The apoptosis tests indicated that
the complexes have an apoptotic effect. Furthermore, complex 1 exhibits more biological activity than complex 2, which is mainly because the area of the aromatic ring of 1,10-phenanthroline is larger than that of 2,2′-bipyridine. 相似文献
20.
Titanium dioxide nanoparticles (TiO 2-NPs) interaction with human serum albumin (HSA) and DNA was studied by UV–visible spectroscopy, spectrofluorescence, circular dichroism (CD), and transmission electron microscopy (TEM) to analyze the binding parameters and protein corona formation. TEM revealed protein corona formation on TiO 2-NPs surface due to adsorption of HSA. Intrinsic fluorescence quenching data suggested significant binding of TiO 2-NPs (avg. size 14.0 nm) with HSA. The Stern–Volmer constant ( Ksv) was determined to be 7.6 × 10 2 M ?1 ( r2 = 0.98), whereas the binding constant ( Ka) and number of binding sites ( n) were assessed to be 5.82 × 10 2 M ?1 and 0.97, respectively. Synchronous fluorescence revealed an apparent decrease in fluorescence intensity with a red shift of 2 nm at Δ λ = 15 nm and Δ λ = 60 nm. UV–visible analysis also provided the binding constant values for TiO 2-NPs–HSA and TiO 2-NPs-DNA complexes as 2.8 × 10 2 M ?1 and 5.4 × 10 3 M ?1. The CD data demonstrated loss in α-helicity of HSA and transformation into β-sheet, suggesting structural alterations by TiO 2-NPs. The docking analysis of TiO 2-NPs with HSA revealed its preferential binding with aromatic and non-aromatic amino acids in subdomain IIA and IB hydrophobic cavity of HSA. Also, the TiO 2-NPs docking revealed the selective binding with A-T bases in minor groove of DNA. 相似文献
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