254-nm Radiation Research Articles

Grey scale structures formation in SU-8 with e-beam and UV

An experimental study of the possibility to fabricate grey scale optical elements and 3D structures in SU-8 resist was carried out. It was found that the negative CAR SU-8 has a contrast smaller than 1 for PEB at a temperature of 20–45 °C and a sensitivity of the order of 1 μC/cm 2 to 20-keV e-beam and 100 mJ/cm 2 to 365-nm UV radiation. Continuous surface relief 3D structures formation in SU-8 by UV exposure was demonstrated both with true grey scale photomasks made with a high-energy beam sensitive glass and binary coded grey scale photomasks. A new technology for 3D self-supporting structure formation in thick SU-8 resist layer was suggested for applications in microfluidics and bioscience. This technique includes anchor elements exposure with UV for the whole resist thickness and a subsequent exposure of the self-supporting fine structures in the upper resist layer only with a low-energy electron beam.

Design of a Membrane Fluorescent Sensor Based on Photo-Cross-Linked PEG Hydrogel

A polymeric hydrogel film was made photochemically for the fluorescent detection of copper ions. An eight-branched PEG macromer having a nitrocinnamate (NC) moiety as the pendant group was synthesized and found to form a gel upon exposure to 365-nm irradiation in the absence of any photoinitiators or catalysts. Peptide 1 (Dns-Gly-His-Lys(NC)) was synthesized with Fmoc solid-phase method and contained three essential parts: a dansyl fluorophore for fluorescent signal transduction, a metal binding site for selective recognition of copper ions from aqueous solution, and a NC group for interaction with PEG-NC macromer. The peptide was found to be efficiently immobilized within the hydrogel network during the photo-cross-linking process. The prepared PEG-NC/1 gel film is strongly fluorescent and can be quenched by the presence of copper ions. The quenching process was reversed by acid treatment and an excellent reversibility was obtained. The designed membrane sensor showed a superior selectivity toward coppe...

Mechanisms for the formation of major oxidation products of adenine upon 365-nm irradiation with 2-methyl-1,4-naphthoquinone as a sensitizer.

Recently we reported the isolation and characterization of N6-formyl- and N6-acetyladenine from 365-nm irradiation of dinucleoside monophosphates d(ApA), d(ApC), and d(CpA) in the presence of 2-methyl-1,4-naphthoquinone (menadione) (Wang et al. Biochem. Biophys. Res. Commun. 2002, 291, 1252-7). In this article we investigated the mechanisms for the formation of the two major products by carrying out photoirradiation with isotopically labeled menadione and 2,3-dimethyl-1,4-naphthoquinone. HPLC and electrospray ionization (ESI)-mass spectrometry (MS) and tandem MS studies of the products unambiguously established that the carbonyl group in the products arises from the photosensitizer: The N6-formyl group comes from oxidation of the methyl group and the N6-acetyl group stems from the methyl group and the adjacent ring carbon in menadione. From above results, we proposed mechanisms for the formation of the two products.

Major Adenine Products from 2-Methyl-1,4-naphthoquinone-Sensitized Photoirradiation at 365 nm

In this article we report the isolation and characterization of major products of adenine in dinucleoside monophosphates upon 2-methyl-1,4-naphthoquinone (menadione)-sensitized UVA irradiation. Our results show that the major products form via the coupling between the menadione moiety and the exocyclic amino group of adenine. Similar reactions were not observed for cytosine. To our knowledge, this is the first report about the direct reaction between a DNA base and a photosensitizer under 365-nm ultraviolet light irradiation. Our results are consistent with previous observation showing that N6 radical formed on adenine upon UVA irradiation.

Protection and Labelling of Thymidine by a Fluorescent Photolabile Group

A fluorescent photolabile group including coumarin and MeNPOC moieties was synthesized to protect 5′-OH terminal function of thymidine (T). Its photochemical and photophysical properties were studied, in particular the photocleavage (photodeprotection under a 365-nm irradiation) is only lowered by a factor of two by addition of the fluorophore. Fluorescence properties of the coumarin probe are not changed upon irradiation, which is satisfactory for the application required, i.e., in situ synthesis of DNA microarrays.

Exposure of Escherichia coli to intestinal myoelectrical activity-related electric field induces resistance against subsequent UV 254nm (UVC) irradiation

Survival of Escherichia coli K-12 AB1157 irradiated with UVC (UV 254nm) was enhanced after pre-treatment with a low-tension electric field (EF). The EF used was identical to the electrical field generated by the small intestine (myoelectrical migrating complex — MMC), registered in a healthy calf and transmitted into the memory of an EF generator. The EF emitted by the generator was transmitted via electrodes placed in shaken bacterial cultures. The protective effects of the EF on the E. coli survival after exposure to UV were: (i) observed only for the dnaJ +dnaK + strain, and not for the Δ dnaJdnaK heat shock mutant; (ii) strictly dependent on the temperature at which the bacteria were grown; (iii) most obvious when the bacteria were incubated at 37°C. Moreover, the MMC-related EF and a higher temperature (40°C) show a similar protective effect against UV-irradiation. The results point to the involvement of the heat shock response in the low-tension EF-induced protection of bacterial cells against UVC-irradiation. Additionally, treatment with the MMC-related EF affects total protein contents and their pattern in E. coli cells. The EF-treatment did not show any influence on the level of the argE3 ochre → Arg + reversions.

Characterization of Ultrasmall CdS Nanoparticles Prepared by the Size-Selective Photoetching Technique

Ultrasmall CdS nanoparticles were prepared by the size-selective photoetching technique. The smallest size of the CdS nanoparticles was obtained by the irradiation with the monochromatic light having the wavelength of 365 nm, while the absorbance of CdS nanoparticles monotonically decreased, for the whole wavelength, to null if the irradiation was performed using a wavelength less than 365 nm. The surface modification of CdS nanoparticles with thiophenol caused the red-shift of the absorption spectra due to the electric interaction between the bound thiophenol molecules and the CdS core, the degree being enhanced with a decrease in the particle size. 1H NMR signals of thiophenol bound on the surface of the smallest CdS nanoparticles prepared by 365-nm irradiation were shifted upfield compared to those obtained for the larger thiophenol-modified CdS nanoparticles prepared by the longer wavelength irradiation, and the signals appeared in positions similar to those of chemically synthesized CdS cluster molec...

Role of dipicolinic acid in survival of Bacillus subtilis spores exposed to artificial and solar UV radiation.

Pyridine-2,6-dicarboxylic acid (dipicolinic acid [DPA]) constitutes approximately 10% of Bacillus subtilis spore dry weight and has been shown to play a significant role in the survival of B. subtilis spores exposed to wet heat and to 254-nm UV radiation in the laboratory. However, to date, no work has addressed the importance of DPA in the survival of spores exposed to environmentally relevant solar UV radiation. Air-dried films of spores containing DPA or lacking DPA due to a null mutation in the DPA synthetase operon dpaAB were assayed for their resistance to UV-C (254 nm), UV-B (290 to 320 nm), full-spectrum sunlight (290 to 400 nm), and sunlight from which the UV-B portion was filtered (325 to 400 nm). In all cases, air-dried DPA-less spores were significantly more UV sensitive than their isogenic DPA-containing counterparts. However, the degree of difference in UV resistance between the two strains was wavelength dependent, being greatest in response to radiation in the UV-B portion of the spectrum. In addition, the inactivation responses of DPA-containing and DPA-less spores also depended strongly upon whether spores were exposed to UV as air-dried films or in aqueous suspension. Spores lacking the gerA, gerB, and gerK nutrient germination pathways, and which therefore rely on chemical triggering of germination by the calcium chelate of DPA (Ca-DPA), were also more UV sensitive than wild-type spores to all wavelengths tested, suggesting that the Ca-DPA-mediated spore germination pathway may consist of a UV-sensitive component or components.

Role of stress responses in human cell survival following exposure to ultraviolet C radiation.

Purpose : To investigate in human skin and other cells the role of tyrosine kinase and protein kinase-C (PKC) in eliciting cell-signalling responses to UV radiation (UVR) that affect the survival of irradiated cells. Materials and methods : The survival of HeLa S3 cells, NCTC 2544 human keratinocytes and A431 human epidermal carcinoma cells was measured following incubation with various tyrosine kinase or PKC inhibitors and exposure to UVC (254nm) radiation. In addition, Western blotting measured PKC isozyme expression in human keratinocytes following UVC exposure. Results : It was confirmed that inhibition of tyrosine kinase activation reduces the survival of UV-irradiated HeLa S3 cells. However, no effect was seen on the survival of either NCTC 2544 human keratinocytes or A431 human epidermal carcinoma cells. In contrast, specific inhibition of PKC reduced the survival of UV-irradiated keratinocytes but had no effect on HeLa cells. Comparison of the effects of different inhibitors in keratinocytes suggested that this effect was mediated mostly through PKC μ and PKC λ/ ı. In addition, keratinocyte exposure to UVC induced large and temporally distinct increases in PKC μ and PKC λ/ ı. Conclusions : The survival of NCTC 2544 keratinocytes, but not HeLa S3 cells, following UVC exposure is mediated by signalling through PKC, mostly PKC μ and PKC λ/ ı. Further study is required to confirm these results in normal human keratinocytes.

UV photolysis of catalase revisited: a spectral study of photolytic intermediates

The 365-nm irradiation of 4.6 μM (≃1.1 mg/ml) catalase solutions in pH 7.4 phosphate buffer induces spectral modifications. Difference spectra show maxima at 434, 555, 584 nm at the beginning of the irradiation, then a final spectrum with a maximum at 568 nm and a shoulder at 530 nm is observed. These results suggest the formation of compound III (oxyferrous catalase) and compound II, respectively. In deaerated 0.1 M, pH 8.7 borate buffer, the ferrous catalase is characterized by maxima at 563 and 594 nm. Hydrogen donors such as ethyl alcohol, formate and p-cresol inhibit, but citrate ions enhance the formation of these intermediates. A mechanism involving Fe(III) reduction according to an internal electron transfer is proposed.

Role of the spore coat layers in Bacillus subtilis spore resistance to hydrogen peroxide, artificial UV-C, UV-B, and solar UV radiation.

Spores of Bacillus subtilis possess a thick protein coat that consists of an electron-dense outer coat layer and a lamellalike inner coat layer. The spore coat has been shown to confer resistance to lysozyme and other sporicidal substances. In this study, spore coat-defective mutants of B. subtilis (containing the gerE36 and/or cotE::cat mutation) were used to study the relative contributions of spore coat layers to spore resistance to hydrogen peroxide (H(2)O(2)) and various artificial and solar UV treatments. Spores of strains carrying mutations in gerE and/or cotE were very sensitive to lysozyme and to 5% H(2)O(2), as were chemically decoated spores of the wild-type parental strain. Spores of all coat-defective strains were as resistant to 254-nm UV-C radiation as wild-type spores were. Spores possessing the gerE36 mutation were significantly more sensitive to artificial UV-B and solar UV radiation than wild-type spores were. In contrast, spores of strains possessing the cotE::cat mutation were significantly more resistant to all of the UV treatments used than wild-type spores were. Spores of strains carrying both the gerE36 and cotE::cat mutations behaved like gerE36 mutant spores. Our results indicate that the spore coat, particularly the inner coat layer, plays a role in spore resistance to environmentally relevant UV wavelengths.

Ultraviolet radiation down-regulates expression of the cell-cycle inhibitor p21WAF1/CIP1 in human cancer cells independently of p53

Purpose : To investigate the regulation of G1 cyclin-dependent kinase inhibitor p21WAF1/CIP1 by ultraviolet (UV) radiation in human carcinoma cells. Materials and methods : Human cancer cell lines were irradiated with UV-C (254nm) radiation, and their responses were characterized by Western blotting, Northern blotting, semi-quantitative RT-PCR analysis, trypan blue staining and flow cytometric cell cycle analysis. Results : At 24 h after UV irradiation, p21 expression was downregulated in various cancer cell types (breast, prostrate, cervix, colon, glioma, squamous cancers), independently of their p53 genetic and functional status. UV-mediated down-regulation of p21 was dose- and time-dependent, was observed at the protein and mRNA levels, and did not correlate with cytotoxicity. Reduction of p21 protein levels required about 4 and 1 h, respectively, in MCF-7 and MDA-MB-231 breast cancer cells; some of the UV-induced decreases in p21 levels in these cell lines was due to enhanced proteasomal degradation. Despite decreased p21 levels, UV-irradiated breast cancer cells with wildtype p53 (MCF-7) retained the capacity for G1 cell-cycle arrest, whereas UV-treated cells with mutant p53 (MDA-MB-231) accumulated in S phase, suggesting a p53-dependent G1 checkpoint in MCF-7. UV treatment caused other alterations in cellcycle regulatory, DNA repair and tumour suppressor genes, as described in this report. Conclusions : In contrast to X-rays, UV causes down-regulation of the cell-cycle inhibitor p21 in tumour cells. It is postulated that this may be an adaptation to promote the growth and survival of transformed cells.

Application of Triaryl Phosphate to Photosensitive Materials (III): Structure and Reactivity of Methyl-Substituted Triaryl Phosphate

Six methyl-substituted triaryl phosphates (TAPs) were synthesized for application as acid generators for thermodeveloping type photosensitive materials [(Aryl-O)3PO; Aryl group, 2-tolyl (ToTP), 3-tolyl (TmTP), 4-tolyl (TpTP), 2,6-xylenyl (TooXP), 2,4-xylenyl (TopXP), and 3,4-xylenyl (TmpXP)]. The TAPs yielded a bisaryl compound and a phosphoric acid monoaryl ester equivalently after photoirradiation with 254-nm radiation. Among these compounds, TmpXP was the most reactive yielding 3,3′,4,4′-tetramethylbiphenyl (78%) after only 4-h irradiation. During the photoirradiation of TAP, strong emissions were detected. Each spectrum had two emission maxima. The shorter wavelength maximum was assigned to monomer fluorescence and the longer one to excimer fluorescence. Emission quenching was carried out by using oxygen. The photosensitivities of thin films of poly(4-trimethylsiloxystyrene) (PSSt) and TAP were studied. Among the films, the PSST-TmpXP thin film was the most sensitive (35 mJ cm−2).

The Regio- and Stereo-chemistries of the (2π+2π) Photocycloaddition of Electron-deficient Ethenes to Isoquinolin-1(2H)-one

The (2π+2π) photocycloaddition of isoquinolin-1(2H)-one to electron-deficient ethenes is efficient, regiospecific and highly stereoselective: 254nm irradiation of the acrylonitrile adduct induces retroadditon and rearrangement to an N-vinylisoindolinone with equal efficiencies.

Chronic UVA (365-nm) irradiation induced scratching in hairless mice: dose-time dependency and the effect of ketanserin.

In a study on the dose-response relationship for longwave UVA (UVA1; 340-400 nm) carcinogenesis in hairless mice scratch marks appeared after months of daily exposure as an unwanted side effect. Tumor induction in the highest of the 4 tested dose groups (receiving a daily dose of 430 kJ/m2 of 365-nm radiation) could not be determined because extensive scarification occurred prior to the development of any tumors. The induction of scratch marks could be scored and quantified in all 4 dose groups tested. The UVA1 dose-dependencies for the induction of tumors and scratch marks were compared. We found that the induction of scratch marks depended mainly on the cumulative UVA1 exposure, whereas tumor induction showed a lesser dose-dependency. An attempt was made to prevent the apparent pruritogenic effect of UVA1 irradiation and to understand its mechanism. The influence of ketanserin, a serotonin/histamine antagonist, on the UVA1 induction of scratch marks was tested in groups of 8 mice daily irradiated with 430 kJ/m2. No difference was found between treated and untreated animals. Histological examination of skin biopsies from irradiated mice from the 430-kJ/m2 dose group from the UVA1 carcinogenic experiment, showed no changes in numbers of mast cells or other inflammatory features when compared to skin biopsies from unirradiated control mice. This indicated that UVA1-induced scratching is not mediated through mast cell release of serotonin and/or histamine. An adequate therapeutic treatment which can prevent UVA1-induced scratching would enable us to test tumor induction with UVA1 over a larger dose range, and may provide additional insight in how this radiation damages the skin. It remains conjectural whether there exists an analogous UVA-induced pruritus in human skin.

UV Irradiation of Shell Eggs: Effect on Populations of Aerobes, Molds, and Inoculated Salmonella typhimurium

The effects were investigated of 254-nm UV radiation on populations of Salmonella typhimurium, aerobes, and molds on the shells of eggs. In the first experiment, the CFU of attached S. typhimurium cells on unwashed clean shell eggs were determined after 0, 1, 3, 5, and 7 min of UV treatment (620 μW/cm2) on both ends of the egg. All UV treatments significantly reduced S. typhimurium CFU (P < .01). UVtreatment (620 μW/cm2) in 1-min alternating light and dark cycles for 5 min (three light and two dark) was compared to 0, 3, and 5 min of UV treatment. No significant differences in microbial populations were observed among light and dark cycles and the other UV treatments. In a subsequent experiment, the same UV treatments were utilized to evaluate photoreactivation. After UV exposure, eggs were exposed to 1 h of fluorescent light or I h of darkness or cultured immediately. S. typhimurium CFU were significantly (P < .01) reduced by the UV treatments. However, no significant differences between microbial populations exposed to UV treatment and UV radiation plus photoreactivation were detected. For studies of aerobic bacteria and molds, different UV treatment times (0, 15, and 30 min) at the intensity of 620 μW/cm2 and different intensities (620, 1350, and 1720 μW/cm2) for 15 min were evaluated. Mold CFU per egg were either 0 or 1 for all UV treatments and a 99% reduction of CFU of aerobic bacteria per egg were observed for all UV treatments. It appears from these studies that UV light can significantly reduce populations of S. typhimurium, aerobes, and molds on shell eggs.

Carcinogenesis induced by UVA (365-nm) radiation: the dose-time dependence of tumor formation in hairless mice.

Although ultraviolet B (UVB wavelengths 280-315 nm) dominates the carcinogenic effect of sunlight, ultraviolet A (UVA 315-400 nm) is estimated to contribute 10-20% to the carcinogenic dose; a substantial background that is not affected by a depletion of the ozone layer. Furthermore, certain high-power modern tanning lamps emit mainly long wave UVA (UVA1; 340-400 nm). For a proper risk estimate of UVA exposure its carcinogenicity relative to that of UVB exposure needs to be determined more accurately. To this end we determined the dose-time relationship for skin tumor induction in hairless mice that were irradiated daily with custom-made Philips 365-nm sources. Irradiation of the group exposed to the highest of the four daily doses (430, 240, 140 and 75 kJ/m2) had to be discontinued because severe scratching set in after 3 months (no tumors). In the lower dose-groups the prevalence curves for skin carcinomas (percentage of tumor-bearing mice versus logarithm of time) ran virtually parallel, and were similar to those found with daily UVB exposure. However, the relationship between the daily dose (D) and the median tumor induction time (t50) appeared to differ: with UVB we found that t50 D(r) = constant, with r = 0.6, whereas with UVA1 we found r approximately 0.4. This would imply that 365-nm carcinogenesis shows less of a dose-dependency than UVB carcinogenesis, and that 365-nm radiation becomes more carcinogenic, relative to UVB, as the daily doses are lowered. This relative shift at low doses complicates extrapolation of UVB to UVA risks in humans. Based on the t50 from the lowest dose-group we found that the carcinogenicity at 365 nm (per J/m2) is 0.9 x 10(-4) times that at 293 nm, the wavelength of maximum carcinogenicity in hairless mice. This result for 365-nm carcinogenicity falls well within the margins of error of the wavelength dependency that was estimated earlier from experiments with broadband UV sources.

Effect of passage number on cellular response to DNA-damaging agents: cell survival and gene expression.

The effect of different passage numbers on plating efficiency, doubling time, cell growth, and radiation sensitivity was assessed in Syrian hamster embryo (SHE) cells. Changes in gene expression after UV or gamma-ray irradiation at different passage numbers were also examined. The SHE cells were maintained in culture medium for up to 64 passages. Cells were exposed to 60Co gamma rays or 254-nm UV radiation. Differential display of cDNAs and Northern blots were used for the study of gene expression. With increasing passage number, SHE cells demonstrated decreased doubling time, increased plating efficiency, and a decreased yield in the number of cells per plate. Between passages 41 and 48 a 'crisis' period was evident during which time cell growth in high serum (20%) was no longer optimal, and serum concentrations were reduced (to 10%) to maintain cell growth. Sensitivity to ionizing radiation was no different between early- and intermediate-passage cells. However, after UV exposure at low passages (passage 3), confluent cells were more sensitive to the killing effects of UV than were log-phase cells. At intermediate passages (passages 43, 48), confluent cells were slightly more radioresistant than were log-phase cells. By passage 64, however, both confluent and log-phase cells showed similar patterns of UV sensitivity. Expression of gamma-actin, PCNA, and p53 transcripts did not change following UV exposure. p53 mRNA was induced following gamma-ray exposure of the intermediate (passage 45) epithelial cells. The observed differences in radiation sensitivity associated with increasing passage number may be influenced by radiation-induced gene expression. We are conducting experiments to identify these genes.

ランプ用蛍光体の量子効率の測定

ランプ用蛍光体の量子効率の測定

Cell damage by UVA radiation of a mercury microscopy lamp probed by autofluorescence modifications, cloning assay, and comet assay

Cell damage by low-power 365-nm radiation of a 50-W high-pressure mercury microscopy lamp was studied. Exposure of Chinese hamster ovary (CHO) cells to ultraviolet-A (UVA) radiation .10 kJ/m2 resulted in significant modifications of nicotinamide adenine dinucleotide (NADH) attributed autofluorescence and inhibition of cell division. Single-cell gel electrophoresis (comet assay) revealed UVA-induced single-strand DNA breaks. According to these results, UVA excitation radiation in fluorescence microscopy may damage cells. This has to be considered in vital cell microscopy, e.g., in calcium measurements.