UV-irradiated Samples Research Articles

Surface characteristics of UV-irradiated chitin-based shape memory polyurethanes

Shape memory polyurethanes (SMPUs) were prepared from polycaprolactone diol 4000 (PCL 4000), 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BDO), chitin, dimethylol propionic acid (DMPA), and triethylamine (TEA). The synthesized samples were irradiated for 50, 100, and 200 h in an UV exposure unit. The effects of chitin and DMPA contents in the polyurethane (PU) formulation on surface properties of the UV-irradiated PU samples were investigated by contact angle measurements, surface free energy and water absorption (%), total work of water adhesion to polymer and equilibrium degree of swelling. Results of the aforementioned surface techniques revealed that the UV-irradiated PU samples were affected by varying the UV exposure period. The interactions of the PU films with solvents on the surface were clearly related to the contents of DMPA and chitin in the final polyurethane formulation and UV-irradiation time.

Dynamic nuclear polarization study of UV-irradiated butanol for hyperpolarized liquid NMR

We have carried out a dynamic nuclear polarization (DNP) study of proton spins of UV-irradiated solid butanol containing phenol at 0.1-1%. By the aid of butyl free radicals produced by the photolysis, the butanol sample was dynamically polarized up to the polarization of 1.4+/-0.1% at 1.5 K and 1.2 T, which is about 4000 times larger than that at the thermal equilibrium at an ambient temperature. Unlike persistent free radicals such as nitroxy and trityl free radicals commonly used for DNP, the butyl free radicals immediately decay by melting. We propose that free radicals produced by UV-photolysis are applicable to the DNP-enhanced hyperpolarized liquid-state NMR (Ardenkjaer-Larsen et al. [6]). The hyperpolarization of the UV-irradiated samples should remain longer than that of the samples having persistent free radicals, because of the absence of the free radicals after the melting in the UV-irradiated samples.

Degraded DNA sample analysis using DNA repair enzymes, mini-STRs and (tri-allelic) SNPs

DNA degradation may cause the loss of the longer short tandem repeat (STR) markers, resulting in DNA profiles with lower discrimination power. We compared standard STR profiling with DNA repair enzyme incubation, and genotyping with mini-STRs or (tri-allelic) single nucleotide polymorphisms (SNPs) in progressively degraded, UV-irradiated DNA samples. In highly degraded DNA samples, most of the standard STR markers fail to amplify, while mini-STRs and especially (tri-allelic) SNPs still provide valuable information.

Green light effects on biological systems: a new biophysical phenomenon.

This paper reports a new phenomenon connected with the influence of green light (GL) on biological systems. Our experiments have revealed an antioxidant effect of GL on cells subjected to lethal doses of UV at the cellular level and a protective effect of GL on DNA denatured by UV, coupled with a structural modification of DNA macromolecules under GL irradiation, at the molecular level. Mouse melanocyte cultures are subjected to UV irradiations with L(50) fluxes of 16.0 J m(-2) s(-1). GL is obtained from a strontium aluminate pigment, which emits GL under UV activation. Cells grown in GL, prior to UV irradiation, present a clear surprising protective effect with surviving values close to the controls. A GL antioxidant effect is suggested to be mediated through GL influence on cellular water cluster dynamics. To test this hypothesis, reactive oxygen species (ROS) are determined in cell cultures. The results revealed a decrease of cellular ROS generation in the UV-irradiated samples protected by a previous 24 h of GL irradiation. At the DNA level, the same type of GL protection against UV damage is recorded by gel electrophoresis and by UV spectroscopy of the irradiated DNA molecules. Two physical methods, impedance spectroscopy and chronoamperometry, have revealed at the level of GL-irradiated DNA molecules spectral modifications that correlate with the UV spectroscopy results. The interaction between the chargeless photons and the field of water molecules from the cellular compartments is discussed in relation with the new field of macroscopic quantum coherence phenomena.

Surface characteristics of UV-irradiated chitin-based polyurethane elastomers

Chitin-based polyurethane elastomers (PUEs) constituted on 4,4′-diphenylmethane diisocyanate (MDI), poly(ε-caprolactone) (PCL) and extended with blends of chitin/1,4-butane diol were first synthesized via two step polymerization technique and then irradiated for 50, 100 and 200 h in an UV exposure chamber as such the spectral distribution of the light is good match for terrestrial solar radiation. The surface properties of the irradiated PU samples were investigated by contact angle measurements, surface free energy and water absorption (%), total work of water adhesion to polymer and equilibrium degree of swelling. The effects of UV-irradiation time and chitin contents in chain extenders (CE) proportion on surface properties were investigated. Results of the aforementioned surface techniques revealed that the UV-irradiated polyurethane samples were affected by varying the UV exposure period.

Kinetics of Microcystis aeruginosa Growth and Intracellular Microcystins Release after UV Irradiation

The release of intracellular microcystins following ultraviolet (UV) irradiation was studied and modeled. Experimental results indicated that 90 mJ cm(-2) of UV fluence were required to inhibit Microcystis aeruginosa growth. The release of intracellular microcystins was also suppressed at higher UV fluence; microcystins concentrations in water did not increase as much in UV-irradiated samples as in controls. A model, based on the following assumptions, was developed to describe the profiles of M. aeruginosa cell number and microcystins concentration in water. Microcystins were contained in M. aeruginosa cells and released only upon cell death. Two types of M. aeruginosa cells existed after UV irradiation; nongrowing cells damaged by UV and growing cells undamaged by UV. To calculate model parameters, these two cell types were counted separately following the addition 0.3 mg L(-1) of cephalosporin, a cell wall synthesis inhibitor. Only growing cells are affected by cephalosporin. The model explained the observed data well, suggesting that the model structure was reasonable. The microcystins release model included release from nongrowing and growing cells. The latter declined as M. aeruginosa growth was inhibited by UV. Release from nongrowing cells was delayed, preventing rapid release of microcystins, which could be explained by a larger reaction order of the decay of nongrowing cells. At 600 and 1800 mJ cm(-2) UV fluence, intracellular microcystins were decomposed by UV, which led to reduced intracellular microcystins release after UV irradiation.

Regulation of Escherichia coli Polynucleotide Phosphorylase by ATP

Polynucleotide phosphorylase (PNPase), an enzyme conserved in bacteria and eukaryotic organelles, processively catalyzes the phosphorolysis of RNA, releasing nucleotide diphosphates, and the reverse polymerization reaction. In Escherichia coli, both reactions are implicated in RNA decay, as addition of either poly(A) or heteropolymeric tails targets RNA to degradation. PNPase may also be associated with the RNA degradosome, a heteromultimeric protein machine that can degrade highly structured RNA. Here, we report that ATP binds to PNPase and allosterically inhibits both its phosphorolytic and polymerization activities. Our data suggest that PNPase-dependent RNA tailing and degradation occur mainly at low ATP concentrations, whereas other enzymes may play a more significant role at high energy charge. These findings connect RNA turnover with the energy charge of the cell and highlight unforeseen metabolic roles of PNPase.

Synaptic Vesicle Protein 2 Binds Adenine Nucleotides

Synaptic vesicle protein 2 (SV2) is required for normal calcium-regulated secretion of hormones and neurotransmitters. Neurons lacking the two most widely expressed isoforms, SV2A and SV2B, have a reduced readily releasable pool of synaptic vesicles, indicating that SV2 contributes to vesicle priming. The presence of putative ATP-binding sites in SV2 suggested that SV2 might be an ATP-binding protein. To explore this, we examined the binding of the photoaffinity reagent 8-azido-ATP[gamma] biotin to purified, recombinant SV2 in the presence and absence of other nucleotides. Our results indicate that SV2A and SV2B bind nucleotides, with the highest affinity for adenine-containing nucleotides. SV2A contains two binding sites located in the cytoplasmic domains preceding the first and seventh transmembrane domains. These results suggest that SV2-mediated vesicle priming could be regulated by adenine nucleotides, which might provide a link between cellular energy levels and regulated secretion.

Studies of photochemical transformations in polystyrene and styrene–maleic anhydride copolymer

Abstract Thin films of polystyrene (PS) and styrene–maleic anhydride copolymer (St-MAn) were exposed to monochromatic UV radiation (254 nm) for varied time intervals. The course of photochemical transformations was monitored by absorption spectroscopy (FT-IR, UV–vis) and thermogravimetry, which were also applied for the estimation of the thermal stability of samples studied. The changes of surface properties were monitored by contact angle measurements. Changes in chemical structure were found in irradiated films (inside and at the surface). The efficiency of photooxidative degradation in St-MAn copolymer was slightly lower than that in PS homopolymer but photo-crosslinking and chromophore formation were enhanced. An increase of hydrophilicity and oxidation degree in UV-irradiated samples was accompanied by destruction processes. The thermal stability of St-MAn was lower in comparison to polystyrene alone. The mechanism of photochemical reactions in the copolymer is proposed.

Preparation and UV weathering of polyethylene nanocomposites

Polyethylene / montmorillonite (PE/MMT) nanocomposites films were prepared by blending in the molten state: Low-density polyethylene (LDPE), montmorillonite clay, and polyethylene grafted maleic anhydride (LDPE-g-MA) or zinc neutralized carboxylate ionomer (Surlyn B) as compatibilizers. A chemically modified clay Cloisite 20A has been used. Nanocomposites were prepared by melt blending in a twin-screw extruder by using two-step mixing. Characterization of the nanocomposites was performed by mechanical properties, X-ray diffraction, light transmittance, infrared spectroscopy (FTIR) and transmission electronic microscope (TEM) techniques. Changes in UV irradiated nanocomposites film samples were characterized by FTIR. The results were analyzed in terms of the effect of the compatibilizing agent in the clay dispersion, and UV degradation of the nanocomposite.

The Effect of Ultraviolet Light Mainly Used for Detecting Latent Fingerprints on STR Typing.

Ultraviolet (UV) light at a wavelength of 254 nm has been used in Japan to detect latent fingerprints. However, the degradation of DNA at 254 nm UV has become a problem for short tandem repeat (STR) typing. In this study, 306 nm UV light that gives a relatively sharp fingerprint image was selected as a new light source for our imaging instrument, and its effect on STR typing was compared to that of the 254 nm UV light. Twenty microliters of saliva and 3 μl of blood were dried on glass slides and irradiated from 5-20 cm with 306 nm or 254 nm UV light for 0.5-30 min. DNA extracted from the UV-irradiated samples was quantified using real-time PCR assay and STR typing was performed. Both wavelengths reduced the amounts of DNA, as irradiated at the shorter distance or for the longer time. However, the reduction of the amount of DNA was less under the 306 nm UV light than the 254 nm. When the 306 nm UV light was irradiated from 5 cm, full STR profiles were obtained from the saliva and blood samples within 10 and 3 min, respectively. In addition, when it was irradiated from 20 cm, full STR profiles were obtained from all the samples in spite of irradiation for 30 min. It was indicated that the 306 nm UV light could be useful as a new light source. However, the use of the 306 nm UV light at a short distance or for a long time should be avoided as much as possible for STR typing.

Magnetic resonance study of the defects influence on the surface characteristics of nanosize anatase

Two anatase samples with crystal size of 11 and 6 nm, prepared by thermal, P11T, and hydrothermal treatments, P6H, of an amorphous TiO 2 precursor, have been studied by 1H nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) to obtain information on how the samples defects influence their surface characteristics. The NMR spectra of the hydrated samples were mainly originated by weakly adsorbed water, more abundant on P6H than on P11T, while most of the spectra obtained after evacuation at 473 K were originated by hydroxyls. P6H presented a larger amount of hydroxyls, some of them with significantly different chemical shifts, than P11T. Those particular hydroxyls are generated by water dissociation at oxygen vacancies. The type and intensity of the signals observed in the EPR spectra of the UV irradiated samples depended on the samples preparation method and on the amount of water weakly adsorbed on the samples. For hydrated P6H, photogenerated electrons are stabilized by Ti 4+ cations at oxygen vacancies, while these electrons can be delocalized in the P11T conduction band. The stabilization of photogenerated holes as O − radicals by low coordinate bridging O 2−, more marked for P6H than for P11T, is favored by weakly adsorbed water. This effect has been attributed to the photodesorption of adsorbed water and protons from acidic bridging hydroxyls, as H 3O + species exchanging protons with adsorbed water, while the hydroxyls bridging O 2− anions trap photogenerated holes.

Structural and morphological changes during UV irradiation of the trans-planar form of syndiotactic polypropylene

Syndiotactic polypropylene films, obtained in the trans-planar mesophase, were exposed to accelerated weathering in a UV device at 45 °C for increasing times. A different series of films, characterized by the same structural organization, was annealed at 45 °C for the same times, to discern the thermal effects from those due to UV irradiation. The influence of UV irradiation and thermal treatments on the structural changes in terms of phase composition, crystallite sizes, and chain conformations was studied. Diffractometric and thermal analyses show that UV radiation causes a strong increase of helical crystallinity (189% with respect to the initial value), leaving the trans-planar mesophase unchanged. The mesophase domains have a higher rigidity and hinder the oxygen diffusion slowing down the photooxidative degradation. The chain scission in the amorphous phase produces a higher mobility, allowing crystallization. The crystallinity also increases in the thermally treated samples, but the increase is limited to the first 48 h and reaches about 89% of the initial value. Both in the thermally treated and UV irradiated samples the crystallite coherence length perpendicular to the 200 planes increases with time. The amorphous chains do crystallize at the beginning near the already formed crystals, thus increasing their dimensions. The carbonyl index shows an induction period of 48 h, before a rapid increase which apparently is inversely proportional to the percentage of mesomorphic and crystalline phases of the irradiated samples, indicating that the photooxidative reactions took place mainly in the amorphous region. A comparison with data already published on the photooxidative behavior of samples crystallized in form I shows that the presence of compact domains in trans-planar mesophase led to an increase in the induction period and to a greater stability of the material in the first 150 h of UV treatment.

Effects of low or medium-pressure UV irradiation on the release of intracellular microcystin

UV irradiation could be an alternative growth inhibition treatment against toxic Microcystis blooms in lakes. This study examined the effect of UV irradiation on the release of toxic intracellular microcystin. Conventional algicidal treatment (e.g. copper sulfate) was known to cause rapid release of intracellular microcystin and additional problems, but no studies have examined the case of UV treatment. A pure culture of Microcystis aeruginosa PCC 7806 was exposed to monochromatic low-pressure or polychromatic medium-pressure UV lamps. Irradiated pure culture suspension was subsequently incubated for 14 days under white light fluorescent lamps. During incubation, profiles of the number of cells, intracellular and extracelluar microcystin concentration were determined. After the UV exposure, the number of cells gradually diminished; the net log cell reduction after 6 days of incubation was 1.6 log or 2.0 log for 600 mJ/cm 2 of LP or MP UV irradiation, respectively. There were three findings for UV irradiation effects on the release of intracellular microcystin. First, because UV exposure can inhibit increases in the number of cells for about 6 days, it inhibited the increase of microcystin concentrations in water. Second, intracellular microcystin was gradually released into the surrounding water through a gradual reduction in the number of cells, preventing a rapid increase of microcystin concentration in water. Microcystin concentration in water was not significantly higher in UV-irradiated samples than non-UV-irradiated sample. Third, UV irradiation was able to degrade intracellular microcystin; it was reduced from 24.6 to 7.06 or 7.16 fg/cell by 600 mJ/cm 2 of LP or MP UV irradiation, respectively. This contributed to reduce increases in microcystin concentrations in water. UV treatment can inhibit Microcystis growth and reduce intracellular microcystin content without rapid release of intracellular microcystin.

Photochemical and thermal behaviours of poly(vinyl alcohol)/graphite oxide composites

The properties of poly(vinyl alcohol)/graphite oxide (PVAL/GO) composites were investigated during UV irradiation using a mercury lamp ( λ = 254 nm). The course of photochemical reactions was monitored by FTIR and UV–vis absorption spectroscopies as well as by estimation of insoluble gel amount formed during crosslinking. Changes in average molecular weights resulting from main chain scission in PVAL were measured by gel permeation chromatography. Composite microstructure was characterized by scanning electron microscopy and X-ray diffraction. The thermal behaviour of composites was determined by a thermogravimetric analysis. It was found that 0.1–5.0% GO addition to polymer bulk slightly hampers photooxidative degradation of PVAL. Thermal degradation in PVAL composites starts at somewhat lower temperatures in the presence of GO but this trend is changed in UV-irradiated samples.

Ultraviolet photolysis of amino acids in a 100 K water ice matrix: Application to the outer Solar System bodies

We report the rates of decomposition by ultraviolet (UV) photolysis of four amino acids in millimeter-thick crystalline water ice matrices at 100 K to constrain the survivability of these important organic molecules within ice lying near the surfaces of outer Solar System bodies. We UV-irradiated crystalline ice samples containing known concentrations of the amino acids glycine, aspartic acid, glutamic acid, and phenylalanine, then we measured the surviving concentrations using high performance liquid chromatography (HPLC) with fluorescence detection. From these experiments, we determine photolytic decomposition rates and half-lives. The half-life varies linearly with the ice thickness for all acids studied here. For example, glycine is the most resistant to photolytic destruction with a half-life of 50, 12, and 3.7 h in 1.6, 0.28, and 0.14 mm thick ices, respectively. We explain this linear variation of half-life with thickness as a consequence of extinction, mostly due to scattering, within these macroscopically thick ice samples. Applied to low latitude surface ice on Jupiter's satellite Europa, this analysis indicates that the concentration of any of these amino acids within the top meter of similar ice will be halved within a ∼10 year timescale.

Vertical distribution of mercury in the Krka river estuary

The concentrations of reactive and total mercury (in the UV-irradiated samples) were measured in unfiltered and acidified samples by atomic absorption. The samples were collected in the vertical profile on one selected station in the Krka river estuary (Croatia) during 1997–2000. The estuary is permanently stratified and characterized by the subsurface temperature maxima. The maximum concentrations of reactive and total mercury range from 0.9 to 3.3 ng L−1, and from 1.3 to 6.0 ng L−1, respectively. The vertical transport of mercury across the picnocline is enhanced under the influence of a north wind.

低圧・中圧紫外線ランプ照射によるダム湖水中の藻類の増殖抑制

Ultraviolet irradiation could be one of the alternatives to conventional treatments against algal bloom. In this study, the efficacy of UV treatment was investigated against the growth of indigenous Microcystis collected from the Terauchi reservoir, which was suffering from algal bloom on the day of sampling. Surface water from the reservoir was subjected to lab-scale UV exposure using a low-pressure UV (LP UV) lamp or a medium-pressure UV (MP UV) lamp. UV-irradiated samples were compared with non irradiated control samples to determine the growth inhibitory effect of UV irradiation. Several exposure conditions were adopted by varying UV fluence and UV fluence rate to investigate their effects on algal growth. The growth inhibition observed after MP UV irradiation was about 3-fold higher than that after LP UV irradiation, up to 50 [mJ · cm-2]. In the case of MP UV irradiation, growth inhibition was almost constant regardless of UV fluence rate at constant UV fluence. A 1.35 [mW · cm-2] UV fluence rate resulted in a growth inhibitory effect 4.6-fold higher than that of a 0.37 [mW · cm-2] UV fluence rate at constant UV fluence in the case of LP UV irradiation. The results of this study indicate that UV irradiation is effective in inhibiting the growth of indigenous Microcystis.

Ultraviolet and ionizing radiation for microorganism inactivation

The impacts of UV irradiation, gamma irradiation, and a combination of both on Escherichia coli inactivation in primary and secondary wastewater effluents were investigated. UV doses of 35 and 62J/m2 were required for a 1-log inactivation of E. coli in the primary and secondary wastewater samples, respectively. A gamma dose of 170Gy (J/kg) was required for a 1-log inactivation of E. coli in both wastewater samples. Variation in gamma radiation dose rates did not have a significant impact on the extent of inactivation at a given total dose. Gamma irradiation of previously UV-irradiated samples indicated that particle-associated microorganisms, which are protected from UV, can be inactivated by ionizing radiation at a rate similar to that for free microorganism inactivation. An estimation of the energy required for disinfection indicated that, in general, the required energy and the energy cost for E. coli inactivation using ionizing radiation are considerably higher than those for UV radiation.

Laser‐Sintered Bismuth Germanate Ceramics as Scintillator Devices

We have investigated the potential use of Bi4Ge3O12 (BGO) laser‐sintered ceramics in scintillator devices for radiation detection. Relevant results from the characterization made during the ceramic processing are presented, such as particle size analysis, X‐ray diffraction studies, and thermal analysis. Furthermore, we have compared the microstructure, relative density, thermoluminescent (TL) emission, and transparency degree of ceramic bodies sintered by CO2 laser heating with a reference set of ceramics sintered in an electrical furnace, and also with single crystals grown by the Czochralski technique. It was observed that the laser‐sintered BGO presented a relative density of 98% (±2%), better pore shrinkage, larger grains, and light transmission intensity 1.5 times higher than the BGO ceramics sintered in a furnace. The TL curves of all samples irradiated with UV and β−rays presented peaks at 75°, 102°, and 143°C, and provided strong indication that the intergrain defects have the same nature of the bulk defects and do not contribute with new traps in the temperature range studied. The relative areas of the total TL emission after β irradiation were 6,0:4,4:1 for the reference ceramic, laser sintered ceramic, and single crystal, respectively. For UV irradiated samples, this relation was 7,1:4,7:1. From these results, we have concluded that laser‐sintered ceramics have an amount of charge traps lower than the conventionally sintered BGO samples, thus having a higher radioluminescence yield.