Induction of DNA strand breaks and DNA-protein cross-links in normal human skin fibroblasts following exposure to 254 nm UV radiation

Levels of DNA strand breaks and DNA-protein cross-links (DPCs) were measured using the alkaline elution assay in normal human skin fibroblasts irradiated with 0-200 J m-2 of 254 nm UV radiation and incubated for 0-24 h. On incubation, the yields of both single-strand breaks (SSBs) and DPCs increased with similar kinetics and remained elevated. In addition, when SSBs were measured under conditions in which DPCs were not eliminated by treatment with proteinase K, a measurable yield of SSBs could not be detected. Hence, the SSBs that form in the UV-irradiated cells following incubation appear to be associated with the DPCs.     

Degradation of a model naphthenic acid, cyclohexanoic acid, by vacuum UV (172 nm) and UV (254 nm)/H2O2

The mechanism of hydroxyl radical initiated degradation of a typical oil sands process water (OSPW) alicyclic carboxylic acid was studied using cyclohexanoic acid (CHA) as a model compound. By use of vacuum ultraviolet irradiation (VUV, 172 nm) and ultraviolet irradiation in the presence of hydrogen peroxide UV(254 nm)/H(2)O(2), it was established that CHA undergoes degradation through a peroxyl radical. In both processes the decay of the peroxyl radical leads predominantly to the formation of 4-oxo-CHA, and minor amounts of hydroxy-CHA (detected only in UV/H(2)O(2)). In UV/H(2)O(2), additional 4-oxo-CHA may also have been formed by direct reaction of the oxyl radical with H(2)O(2). The oxyl radical can be formed during decay of the peroxyl-CHA radical or reaction of hydroxy-CHA with hydroxyl radical. Oxo- and hydroxy-CHA further degraded to various dihydroxy-CHAs. Scission of the cyclohexane ring was also observed, on the basis of the observation of acyclic byproducts including heptadioic acid and various short-chain carboxylic acids. Overall, the hydroxyl radical induced degradation of CHA proceeded through several steps, involving more than one hydroxyl radical reaction, thus efficiency of the UV/H(2)O(2) reaction will depend on the rate of generation of hydroxyl radical throughout the process. In real applications to OSPW, concentrations of H(2)O(2) will need to be carefully optimized and the environmental fate and effects of the various degradation products of naphthenic acids considered.     

Action spectra for oxygen-dependent and independent inactivation of Escherichia coli WP2s from 254 to 460 nm.

Abstract— Action spectra for lethality of E. coli WP2s under aerobic and anaerobic conditions. based on final slopes of the survival curves, reveal the absence of oxygen dependence at 313 nm and shorter wavelengths and a strong oxygen dependence (OER of 12 at 334 nm and 16 at 365 nm) at wavelengths longer than 313 nm. Shoulders or small peaks at 340, 365 , 410 and 500 nm suggest the participation of non-DNA chromophores in aerobic lethality at these wavelength ranges.     

地表水中254nm波长紫外吸光值与CODMn及CODCr关系的探讨

通过实验探讨了地表水254nm波长紫外吸光值与地表水中CODMn及CODCr之间的关系。     

Simultaneous measurements of visible (400-700 nm) and infrared (3.4 microm) NO(2) absorption

Laboratory measurements of NO(2) absorption were obtained in the visible (400-700 nm) and mid-infrared (3.4 mum) regions simultaneously using SCISAT-1's ACE-FTS (atmospheric chemistry experiment-Fourier transform spectrometer) and MAESTRO (measurement of aerosol extinction in the stratosphere and troposphere retrieved by occultation) spectrometers. An intercomparison of these measurements was used to verify the consistency between the HITRAN 2004 3.4-mum band strengths and the strengths of three different visible cross section data sets. These measurements should be of interest to the remote-sensing community, since NO(2) measurements obtained by infrared-range instruments are often compared to those obtained by visible-range instruments without accurate knowledge of the consistency between the visible and infrared absorption coefficients. Two significant results were obtained in this study: (1) A 0.5% agreement was found between the HITRAN 2004 line strengths and the Vandaele et al. (Vandaele, A. C.; Hermans, C.; Fally, S.; Carleer, M.; Colin, R.; Mérienne, M.-F.; Jenouvrier, A.; Coquart, B. J. Geophys. Res. 2002, 107 (D18), 4348) temperature-corrected cross sections, and (2) the mean pressure-broadened half-width of NO(2) by NO in the 3.4-mum band was measured as being 0.096 +/- 0.001 cm(-1) atm(-1). The latter finding is thought to be unreported by the literature.     

Action spectra for modification of Escherichia coli B/r menaquinone by near-ultraviolet and visible radiations (313-578 nm)

–Menaquinone-8 (MQ-8) was irradiated in vivo in Escherichia coli B/r and in vitro after extraction from E. coli B/r, using monochromatic radiation in the range 313–578 nm. Within experimental error, the action spectra for loss of chromatographic mobility after irradiation in vivo and in vitro agree 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 vivo at 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, of E. coli B/r. The quantum yield for this reaction in vivo at 334 nm has the very high value of 0.26. The high sensitivity of MQ-8 suggests involvement in near-UV-induced effects on the plasma membrane.     

Absorption cross-sections of NO2 in the UV and visible region (200 – 700 nm) at 298 K

The absorption cross-sections of NO₂ have been measured in the wavelength range 200 – 700 nm at 298 K with a spectral resolution of 0.04 nm. The data were acquired digitally, allowing post-processing such as integration in different wavelength intervals. The cross-sections are averaged over 1 nm intervals and over the atmospheric wavelength intervals used in solar photolysis calculations.     

Role of Cell Surface Lipopolysaccharides in Escherichia coli K12 adhesion and transport

The influence of bacterial surface lipopolysaccharides (LPS) on cell transport and adhesion has been examined by use of three mutants of Escherichia coli K12 with well-characterized LPS of different lengths and molecular composition. Two experimental techniques, a packed-bed column and a radial stagnation point flow system, were employed to investigate bacterial adhesion kinetics onto quartz surfaces over a wide range of solution ionic strengths. Although the two systems capture distinct deposition (adhesion) mechanisms because of their different hydrodynamics, similar deposition kinetics trends were observed for each bacterial strain. Bacterial deposition rates were directly related to the electrostatic double layer interaction between the bacteria and quartz surfaces, in qualitative agreement with classic Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. However, DLVO theory does not fully explain the deposition behavior for the bacterial strain with the lengthy, uncharged O-antigen portion of the LPS. Neither the length nor the charge characteristics of the LPS molecule directly correlated to deposition kinetics, suggesting a complex combination of cell surface charge heterogeneity and LPS composition controls the bacterial adhesive characteristics. It is further suggested that bacterial deposition behavior is determined by the combined influence of DLVO interactions, LPS-associated chemical interactions, and the hydrodynamics of the deposition system.     

Induction of single-strand breaks (alkali-labile bonds) in bacterial and phage DNA by near UV (365 nm) radiation

Abstract —Irradiation at 365 nm results in the induction of approximately 2–4 times 10^-6 and 1-2times 10^-6 single-strand breaks (alkali-labile bonds) per 10⁸ daltons per J m^-2 in extracted phage T4 DNA and in Escherichia coli bacterial DNA, respectively. The rate of break induction in DNA of intact phage is approximately one-fourth that for extracted phage DNA. 2-aminoethylisothiouronium bromide-HBr protects against break induction in both phage systems. No breaks are induced in the DNA of bacteria irradiated under anaerobic conditions over the dose range tested. Possible induction mechanisms are suggested. Consideration is given to the relative importance of pyrimidine dimers and single-strand breaks in the bactericidal action of 365 nm radiation.     

Intercomparison of simultaneously obtained infrared (4.8 microm) and visible (515-715 nm) ozone spectra using ACE-FTS and MAESTRO

Laboratory ozone absorption spectra were measured simultaneously in the visible (515-715 nm) and infrared (2070-2140 cm(-1)) spectral regions using SCISAT-1's MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and ACE-FTS (Atmospheric Chemistry Experiment-Fourier Transform Spectrometer) spectrometers. An intercomparison of these measurements was used to assess the relative accuracy of HITRAN absolute line strengths, for which there was a 4% change between the 2000 and 2004 versions. Results reported here show that Chappuis band cross section strengths are more consistent with the HITRAN 2004 4.8 microm band line strengths than with the 2000 compilation.     

The molecular mechanism of dicarboxylic acid transport in Escherichia coli K 12.

It is the purpose of this communication to review the properties of the dicarboxylic acid transport system in Escherichia coli K 12, in particular the role of various dicarboxylate transport proteins, and the disposition of these components in the cytoplasmic membrane. The dicarboxylate transport system is an active process and is responsible for the uptake of succinate, fumarate, and malate. Membrane vesicles prepared from the EDTA, lysozyme, and osmotic shock treatment take up the dicarboxylic acids in the presence of an electron donor. Genetic analysis of various transport mutants indicates that there is only one dicarboxylic acid transport system present in Escherichia coli K 12, and that at least 3 genes, designated cbt, dct A, and dct B, are involved in this transport system. The products corresponding to the 3 genes are: a periplasmic binding protein (PBP) specified by cbt, and 2 membrane integral proteins, SBP 1 and SBP 2, specified by dct B and dct A, respectively. Components SBP 1 and SBP 2 appear to be exposed on both the inner and outer surfaces of the membrane, and lie in close proximity to each other. The substrate recognition sites of SBP 2 and SBP 1 are exposed on the outer and inner surfaces of the membrane respectively. The data presently available suggest that dicarboxylic acids may be translocated across the membrane via a transport channel. A tentative working model on the mechanism of translocation of dicarboxylic acids across the cell envelope by the periplasmic binding protein, and the 2 membrane carrier proteins is presented.     

Study on continuous (254 nm) and pulsed UV (266 and 355 nm) lights on BVD virus inactivation and its effects on biological properties of fetal bovine serum

Both continuous UV lights and pulsed UV lasers have potentials to inactivate known and emerging viruses. Bovine viral diarrhea virus (BVDV), from the Pestivirus genus, is known to be a common viral contamination in (fetal) bovine serum (FBS). Also, BVDV has been used in the blood product industry as a surrogate for Hepatitis C virus (HCV), due to its similarity in structure and genome. Germicidal UV lamp with the wavelength of 254 nm and Nd:YAG laser (pulsed UV laser) in its third and fourth harmonic with the wavelengths of 355 and 266 nm, respectively, were used. BVDV suspended in PBS or FBS were exposed to different intensities and doses and then reduction in BVDV titer were calculated. To complete inactivation of BVDV suspended in PBS and PBS containing 5% FBS, 1.6 (t = 30 min) and 3.2 (t = 60 min) J/cm² were used. The minimum doses for inactivation of BVDV suspended in PBS with the 355 and 266 nm of pulsed UV laser were 352 and 92.25 J/cm². Also, the minimum doses for inactivation of BVDV suspended in FBS with 355 and 266 nm wavelengths of pulsed UV laser were 704 and 127 J/cm². To evaluate the irradiated FBS quality to support cell culture growth, FBS was treated with the dose of 190.5 J/cm² and 266 nm pulsed UV laser and was used to grow Vero cells, in comparison with a control group. The viability of cells in two groups was identical and the statistical evaluation showed no significant difference in 12 passages.     

MUTATION AND SISTER CHROMATID EXCHANGE INDUCTION IN CHINESE HAMSTER OVARY (CHO) CELLS BY PULSED EXCIMER LASER RADIATION AT 93 nm AND 308 nm AND CONTINUOUS UV RADIATION AT 254 nm

We compared mutagenesis and sister chromatid exchange (SCE) induction by 193 nm and 308 nm pulsed excimer laser radiation with 254 nm low intensity continuous wave UV light in Chinese hamster ovary (CHO) cells in culture. The 254 nm radiation was most mutagenic of the radiations, in accordance with expectation, and also was most effective in increasing the level of SCEs. The 193 nm radiation was mutagenic at the ouabain resistance locus, but not at the HGPRT locus. However, 193 nm radiation was also strongly cytotoxic at energies producing measurable mutations. This radiation also caused a dose-related increase in SCEs. Pulsed excimer radiation at 308 nm was mutagenic at both loci, and also increased the incidence of SCEs. Comparison of the ratio of mutants/surviving cells at the D37 after radiation showed similar values for 254 nm and 308 nm at the HGPRT locus, but at the ouabain resistance locus, the ratio for the 308 nm radiation was about 5 times that for 254 nm radiation. These results indicate that some risk for mutagenesis may accompany the use of excimer radiation in the UVA region in therapeutic applications.     

A study of product ratios in the direct (313 nm) and Hg-sensitized (254 nm) photodecomposition of 2-methylcyclohexanone in the gas phase

The photolysis of 2-methylcyclohexanone has been studied in the gas phase at 313 nm, mainly at 100°C, over a range of pressures. The Hg(6³P₁) photosensitized decomposition has also been investigated at 100°C. Under conditions of high excitation and/or little collisional quenching the major products are carbon monoxide and the hydrocarbons: 1-hexene, trans-and cis-2-hexene and methylcyclopentane, with minor aldehyde formation. The various product ratios are presented in tabular form. At lower excitation energies, and with increased collisional deactivation, trans- and cis-5-heptenal become important products, and the trans/cis aldehyde ratio is seen to be slightly pressure dependent when all the systems are compared. Similarly, there is a small pressure dependence for the Σ hexenes/methylcyclopentane ratio. From experiments at 250°C the temperature dependence of this ratio was established, and for thermalized hexane-1,5-diyl an activation energy difference (E_d ? E_c) = ?1.3 kcal mol^?1 has been determined for the disproportionation and combination of the biradical. The mechanism for the photolysis is discussed in terms of triplet state photochemistry and biradical intermediates as developed, in particular, by Frey and coworkers, this Journal, 16 , 1337 (1984).     

Double ionization of quaterrylene (C40H20) in water-ice at 20 K with Ly alpha (121.6 nm) radiation

Polycyclic aromatic hydrocarbon (PAH) molecules undergo facile ionization in cryogenic water-ices resulting in near quantitative conversions of neutral molecules to the corresponding singly charged radical cations. Here we report, for the first time, the production and stabilization of a doubly ionized, closed shell PAH in water-ice. The large PAH quaterrylene (QTR, C40H20) is readily photoionized and stabilized as QTR 2+ in a water-ice matrix at 20 K. The kinetic analysis of photolysis shows that the QTR 2+ is formed at the expense of QTR +, not directly from QTR. The long-axis polarized S1-S0 (1(1)B(3u) <-- 1(1)Ag) transition for QTR 2+ falls at 1.59 eV (782 nm). TD-DFT calculations at the B3LYP level predict that this transition falls at 1.85 eV (670 nm) for free gas-phase QTR 2+, within the 0.3 eV uncertainty associated with these calculations. This red shift of 0.26 eV is quite similar to the 0.24 eV red shift between the TD-DFT computational prediction for the lowest energy transition for QTR + (1.68 eV) and its value in a water matrix (1.44 eV). These results suggest that multiple photoionization of such large PAHs in water-ice can be an efficient process in general.     

Comparison of the Disinfection Effects of Vacuum-UV (VUV) and UV Light on Bacillus subtilis Spores in Aqueous Suspensions at 172, 222 and 254 nm

The efficacy of UV and vacuum-UV (VUV) disinfection of Bacillus subtilis spores in aqueous suspensions at wavelengths of 172, 222 and 254 nm was evaluated. A Xe₂* excilamp, a KrCl* excilamp and a low-pressure mercury lamp were used as almost monochromatic light sources at these three wavelengths. The first-order inactivation rate constants at 172, 222 and 254 nm were 0.0023, 0.122 and 0.069 cm² mJ⁻¹, respectively. Therefore, a 2 log reduction of B .  subtilis spores was reached with fluences (UV doses) of 870, 21.6 and 40.4 mJ cm⁻² at these individual wavelengths. Consequently, for the inactivation of B .  subtilis spores, VUV exposure at 172 nm is much less efficient than exposure at the other two wavelengths, while exposure at 222 nm is more efficient than that at 254 nm, which is probably because triplet energy transfer from DPA to thymine bases at 222 nm is higher than that at 254 nm. This research indicated quantitatively that VUV light is not practicable for microorganism disinfection in water and wastewater treatment. However, in comparison with other advanced oxidation processes ( e.g. UV/TiO₂, UV/H₂O₂ or O₃/H₂O₂) the VUV-initiated photolysis of water is likely more efficient in generating hydroxyl radicals and more effective for the inactivation of microorganisms.     

THE EFFECTS OF EXOGENOUS CATALASE ON BROAD-SPECTRUM NEAR-UV (300-400 nm) TREATED Escherichia coli CELLS

Abstract —Catalase incorporated into plating medium protects against inactivation and mutagenesis by broad-spectrum near-ultraviolet wavelength (300-400 nm) (NUV) radiation in strains of Escherichia coll . Plating medium containing catalase does not provide protection against inactivation by wavelengths in the FUV region. Catalase added to the cell suspension during or added immediately after NUV exposure also protects against inactivation. The protection provided by catalase suggests a possible role for hydrogen peroxide in the processes of inactivation and mutagenesis by broad-spectrum NUV.     

DNA Photodamage, Repair, Gene Induction and Genotoxicity Following Exposures to 254 nm UV and 8-Methoxypsoralen Plus UVA in a Eukaryotic Cell System

The induction and repair of different types of photodamage and photogenotoxicity in eukaryotic cells have been the subject of many studies. Little is known about possible links between these phenomena and the induction of DNA damage-inducible genes. We explored this relationship using the yeast Saccharomyces cerevisiae, a pertinent eukaryotic model. Previous results showed that the photogenotoxic potential of 8-methoxypsoralen (8-MOP) plus UVA is higher than that of UV (254 nm). Moreover, the induction of the ribonucleotide reductase gene RNR2 by UV and 8-MOP plus UVA in an RNR2-LACZ fusion strain and the formation of DNA double-strand breaks (dsb) as repair intermediates after such treatments suggest that the latter process could involve a signal for gene induction. To further substantiate this, we measured the induction of the DNA repair gene RAD51 in RAD51-LACZ fusion strains using the dsb repair and recombination deficient mutant rad52 and the corresponding wild type, and we determined the formation of dsb by pulsed-field gel electrophoresis. After treatments, the resealing of dsb formed as repair intermediates was impaired in the rad52 mutant. At equal doses, i.e. the same number of lesions, the induction of the RAD51 gene by UV or 8-MOP plus UVA was significantly reduced in the rad52 mutant as compared with the wild type. The same was true when equitoxic doses were used. Thus, the RAD52 repair pathway appears to play an important role not only in dsb repair but also in gene induction. Furthermore, the signaling pathways initiated by DNA damage and its processing are somewhat linked to the photogenotoxic response.