Porphyrin deposition induced by UV irradiation

Simple irradiation by UV light of porphyrin TpyP and its zinc(II) and manganese(III) metal derivatives in chlorinated solvents leads to the deposition on silica of mesoscale aggregates. The process is due to the photochemical decomposition of the solvent with generation of HCl, which causes the precipitation of a protonated form. The morphology of the resulting objects is driven by the nature of the inserted metal ion.     

Neutravidin micropatterning by deep UV irradiation

We describe a novel approach for directly patterning neutravidin protein by exposure to deep UV irradiation. Neutravidin is physically absorbed onto the glass or quartz substrate, dehydrated in acetone and air-dried. Dry neutravidin-coated samples are patterned either by top-side or back-side exposure to 185 nm UV. Subsequent introduction of fluorescent biotinylated proteins clearly demonstrates binding to the masked neutravidin regions and no binding to exposed areas. Patterned samples retain their protein affinity for at least three months of storage at room temperature.     

Conversion of SB 203580-insensitive MAP kinase family members to drug-sensitive forms by a single amino-acid substitution

Background: Specific inhibitors of protein kinases have great therapeutic potential, but the molecular basis underlying their specificity is only poorly understood. We have investigated the drug SB 203580 which belongs to a class of pyridinyl imidazoles that inhibits the stress-activated protein (SAP) kinases SAPK2a/p38 and SAPK2b/p38β2 but not other mitogen-activated protein kinase family members. Like inhibitors of other protein kinases, SB 203580 binds in the ATP-binding pocket of SAPK2a/p38. Results: The SAP kinases SAPK1γ/JNK1, SAPK3 and SAPK4 are not inhibited by SB 203580, because they have methionine in the position equivalent to Thr106 in the ATP-binding region of SAPK2a/p38 and SAPK2b/p38β2. Using site-directed mutagenesis of five SAP kinases and the type I and type II TGFβ receptors, we have established that for a protein kinase to be inhibited by SB 203580, the sidechain of this residue must be no larger than that of threonine. Sensitivity to inhibition by SB 203580 is greatly enhanced when the sidechain is even smaller, as in serine, alanine or glycine. Thus, the type I TGFβ receptor, which has serine at the position equivalent to Thr106 of SAPK2a/p38 and SAPK2b/p38β2, is inhibited by SIB 203580. Conclusions: These findings explain how drugs that target the ATP-binding site can inhibit protein kinases specifically, and show that the presence of threonine or a smaller amino acid at the position equivalent to Thr106 of SAPK2a/p38 and SAPK2b/p38β2 is diagnostic of whether a protein kinase is sensitive to the pyridinyl imidazole class of inhibitor.     

Production of CO by UV irradiation of acetylacetone

Photochemistry of hexafluoroacetylacetone has been studied by photoproduct analysis using infrared spectroscopy. Hexafluoroacetylacetone was irradiated by KrF excimer laser with the oscillation wavelength of 248 nm during 100 s and the photoproducts were analyzed by transmittance measurement of FT-IR in the spectral region between 3500 and 1300 cm⁻¹. One of the photoproducts was CO. It was estimated that the formation efficiency of CO was approximately 0.6.     

Somatic-cell mutation induced by UVA and monochromatic UV radiation in repair-proficient and -deficient Drosophila melanogaster

Near-ultraviolet light (UVA: 320-400 nm) constitutes a major part of sunlight UV. It is important to know the effect of UVA on the biological activities of organisms on the earth. We have previously reported that black light induces somatic-cell mutation in Drosophila larvae. To investigate which wavelength of the UVA is responsible for the mutation we have now carried out a series of monochromatic irradiations (310, 320, 330, 340, 360, 380 and 400 nm) on Drosophila larvae, using the large spectrograph of the National Institute for Basic Biology (Okazaki National Research Institutes, Okazaki, Japan). Mutagenic activity was examined by the Drosophila wing-spot test in which we observe mutant wing hair colonies (spots) on the wings of adult flies obtained from the treated larvae. The induction of mutation was highest by irradiation at 310 nm and decreased as the wavelength became longer. Neither the 380 nor the 400 nm light was mutagenic. Excision repair is known to protect cells from UV damage. In the excision-repair-deficient Drosophila, the mutagenic response induced by 310 nm irradiation was 24-fold higher than that of the wild-type (7.2 +/- 1.5 spots/wing/kJ vs 0.3 +/- 0.08 spots/wing/kJ), and at 320 nm the difference of the response was 14-fold (0.21 vs 0.015 +/- 0.005). In the case of irradiation at 330 and 340 nm the difference of the response was only two-fold (at 330 nm, 6.9 +/- 2.9 x 10(-3) vs 3.1 +/- 1.1 x 10(-3) spots/wing/kJ; at 340 nm, 3.5 +/- 0.9 x 10(-3) vs 2.0 +/- 0.7 x 10(-3). These results suggest that the lesion caused in the larvae by 320 nm irradiation may be similar to the damage induced by 310 nm and that the lights of 330 and 340 nm may induce damage different from the lesions induced by shorter-wavelength lights.     

Preparation and characterization of DNA films induced by UV irradiation

Large amounts of DNA-enriched materials, such as salmon milts and shellfish gonads, are discarded as industrial waste. We have been able to convert the discarded DNA to a useful material by preparing novel DNA films by UV irradiation. When DNA films were irradiated with UV light, the molecular weight of DNA was greatly increased. The reaction was inhibited by addition of the radical scavenger galvinoxyl suggesting that the DNA polymerization with UV irradiation proceeded by a radical reaction. Although this UV-irradiated DNA film was water-insoluble and resistant to hydrolysis by nuclease, the structure of the DNA film in water was similar to non-irradiated DNA and maintained B-form structure. In addition, the UV-irradiated DNA film could effectively accumulate and condense harmful DNA-intercalating compounds, such as ethidium bromide and acridine orange, from diluted aqueous solutions. The binding constant and exclusion number of ethidium bromide for UV-irradiated DNA were determined to be 6.8 +/- 0.3 x 10(4) M(-1) and 1.6 +/- 0.2, respectively; these values are consisted with reported results for non-irradiated DNA. The UV-irradiated DNA films have potential uses as a biomaterial filter for the removal of harmful DNA intercalating compounds.     

Ageing of butyl rubber against UV irradiation

The photodegradation and stabilisation of butyl rubber have been studied in air in the temperature range of 258 to 318 K using a monochromatic light of 366 nm with a constant intensity flux of 1·68×10⁻⁸ einstein s⁻¹ cm⁻² in the absence and presence of cuprous di-isopropyl dithiophosphate. Irradiations were carried out on films at 0, 2, 4, 6, 8, 10, 12 and 14 h. An investigation into the nature and molecular changes during the irradiation with ultra-violet light (366 nm) of butyl rubber has been conducted by light scattering technique. The quantum yields of the photolysis of the polymer have been determined using a potassium ferrioxalate actinometer. Light scattering data have been processed to yield the activation energies in the absence and presence of 0·1 wt. % stabiliser. The incorporation of 0·7 wt. % cuprous di-isopropyl dithiophosphate in the matrix of the rubber film exercises the maximum protective influence on the photolytic degradation of the rubber.     

Synthesis of gold nanoparticles by reduction of HAuCl4 under UV irradiation

Gold nanoparticles were prepared in surfactant solutions by reduction of HAuCl₄ under UV irradiation without adding extra reductants or other organic substances. The effect of the structure and the property of surfactant on the size and the optical properties of prepared gold nanoparticles were studied. It was found that the longer the alkyl chain of the surfactant, the larger gold particles are obtained. On the other hand, lengthen the geminis spacer benefits the formation of smaller gold particles. The formation of adduct micelles composed of the charged surface active portion of the surfactant molecule and the (Au^IIICl₄)⁻ ion in cationic surfactant solution serves as the gold source and favors the formation of gold particles with larger sizes. While the repulsion between the (Au^IIICl₄)⁻ ion and the negative charged surface of anionic surfactant micelle is in favor of the formation of gold nanoparticles with smaller sizes. The nonionic surfactants can also assist the formation of dispersed gold nanoparticles.     

Growth of carbonyl index in the degradation of polypropylene by UV irradiation

The growth of the carbonyl index in the degradation of polypropylene by UV irradiation, with and without UV stabilizer, has been measured and interpreted. From the kinetics of the degradation process the mathematical expression of the growth of the carbonyl index was derived using the steady-state treatment for short-lived intermediates, except for the alkyl radical P. For polypropylene without UV stabilizer and for polypropylene with UV absorber or excited-state quencher, the growth of the carbonyl index was related to UV irradiation time by X = Ae^λ1t + Be^λ2t. While in the presence of an antioxidant or radical scavenger, the general form was X = Ae^λ1t + Be^λ2t + C. The values of A, B, λ₁, λ₂, and C were obtained by fitting the experimental data into the equation. It was found that the error was about 15%.     

Identification of free radicals induced by UV irradiation in collagen water solutions

Electron paramagnetic resonance (EPR) method has shown that hydrogen atoms and acetic acid free radicals appear in surrounding acetic acid-water solution of collagen under ultraviolet (UV) irradiation. These free radicals interact with the collagen molecule; consequently, seven superfine components of EPR spectrum with the split of aH = 11.3G and g-factor 2.001 appear. It is assumed that this spectrum is related to the free radical occurred on the proline residue in collagen molecule. In order to discover .OH hydroxyl radicals even in minor concentration, spin trap 5.5-dimethyl-1-pyrroline N-oxide (DMPO) has been applied. During the irradiation of collagen water solution in the presence of spin trap, EPR spectrum of the DMPO/.OH adduct has not been identified, while the above mentioned spectrum has been observed once the hydrogen peroxide H2O2 and FeSO4 were added to the sample. That means that water photolysis does not take place in collagen water-solution due to UV irradiation. It was suggested that occurrence of hydrogen radical is connected with the electron transmission to the hydrogen ion. The possible source of free electrons can be aromatic residues, photo ionization of which takes place in collagen molecule due to UV irradiation.     

Determination of selenium in freshwaters by cathodic stripping voltammetry after UV irradiation

An analytical method was developed for the determination of total dissolved selenium in fresh waters, using linear sweep cathodic stripping voltammetry (CSV) in combination with UV photolytic digestion. Both the CSV method, based on the electrodeposition and stripping of Cu(2)Se, and the UV irradiation procedure were investigated in detail. In the presence of dissolved organic substances, as in freshwaters, Se(VI) is reduced to Se(IV) by UV irradiation in 0.1M hydrochloric acid. Glucose can be used as the carbon source in samples low in natural dissolved organic carbon (DOC). The photolytic yields of Se(IV) were about 90% in both cases. Five freshwater samples were analysed for total selenium by CSV after UV photolysis, and by hydride generation atomic absorption spectrometry (HG-AAS) after oxidative digestion followed by reduction with hydrochloric acid. The results agreed well and the concentrations were in the range 70-190 ng/l., well above the detection limit of the CSV method at 2 ng/l.     

Anisotropic surface morphology of azopolymer films generated by polarized UV light irradiation

X-ray reflectivity measurements reveal anisotropy of the vertical surface roughness caused by exposure to linearly polarized UV (LPUV) light in the films of two azopolymers. The irradiated surface is found to have higher roughness in the direction parallel to the direction of polarization than in the orthogonal direction. The photo-modification of the surface morphology is caused by spatial changes induced in polymer films by LPUV irradiation. The important role of surface roughness anisotropy in determining the alignment of liquid crystals is discussed.     

Regeneration of photocatalysts by in situ UV irradiation in photocatalytic membrane reactor

ZnO was successfully prepared by the conventional synthetic route. Polyvinylpyrrolidone was used as soft-template to synthesize ZnO with controllable size and shape. It was found that ZnO was synthesized with average crystal size of 49 nm, as reported by an X-ray diffraction experiment. Scanning electron microscopy and transmission electron microscopy confirmed the hexagonal shape of the as-synthesized ZnO. The thus prepared ZnO colloidal particles exhibited numerous opportunities for numerous applications.     

Anisotropic surface morphology of azopolymer films generated by polarized UV light irradiation

X-ray reflectivity measurements reveal anisotropy of the vertical surface roughness caused by exposure to linearly polarized UV (LPUV) light in the films of two azopolymers. The irradiated surface is found to have higher roughness in the direction parallel to the direction of polarization than in the orthogonal direction. The photo-modification of the surface morphology is caused by spatial changes induced in polymer films by LPUV irradiation. The important role of surface roughness anisotropy in determining the alignment of liquid crystals is discussed.     

Polymerization of micelles under irradiation with UV light

Micelle formation behavior of sodium salts of fatty acids containing double bond at the chain end, sodium 10-undecenoate (Na-10-U) and sodium 8-nonenoate (Na-8-N), was examined with measurement of electric conductivity of their aqueous solutions, and the plot of the electric conductivity against the concentration for each fatty acid was found to show two break points; at 0,044 and 0,12mol/1 for Na-10-U and at 0,16 and 0,44 mol/1 for Na-8-N. The similar behaviors of the aqueous solutions were also found with the measurements of the maximum amount of solubilized benzene into the aqueous solution and of the solution viscosity, and the concentrations corresponding to the break points were assumed to be first and second critical micelle concentrations (CMC's), respectively. Polymerization of the sodium salts under irradiation with UV light was investigated. For each fatty acid, the amount of the obtained polymer was very small at very low concentrations of the fatty acid, but it increased rapidly with increasing concentration of the monomer at concentrations higher than the first CMC and then mildly at the concentrations higher than the second CMC. Number-average degrees of polymerization of the polymers obtained were measured with a gel permeation chromatography technique and found to be up to 13 for Na-10-U and 8,5 for Na-8-N.     

Cyclometalation of phosphorus ligands by UV irradiation of complexes having transition metal---silicon bonds

UV irradiation of complexes of the type (η⁵-C₅H₅)(CO)_nMSiR₃ (n = 2, M = Fe; n = 3, M = Mo) in the presence of phosphorus ligands such as P(XC₆H₅)₃ (X = O, S, CH₂) and phosphines containing allyl, 1-naphthyl or tolyl groups gives cyclometalated complexes, R₃SiH being eliminated with retention of configuration at Si. In the cyclometalation five-membered rings are formed in preference to six-membered rings, and metalation occurs more easily at sp² than at sp³ carbon atoms. Methylphenyl-1-naphthylphosphine undergoes rapid racemization upon UV irradiation at room temperature.     

Enzyme activation and inactivation induced by low doses of irradiation

Activation phenomenon has been observed with two sets of enzymes under the conditions of low dosage irradiation. Activation was registered for angiotensin-converting enzyme under in vitro γ-irradiation (0.662 MeV, pulse duration approx 10s) at dose levels of 1–3 Gy and under X-ray irradiation (approx 9 keV, pulseduration approx 10^?9s) at dose levels of 2×10^?5 Gy. An activation effect has also occurred for native and recombinant horseradish peroxidase and tobacco peroxidase under γ-irradiation. The phenomenon observed is rationalized in terms of a kinetic model suggesting the existence of at least one activated enzyme conformation induced by radiolysis. The activity oscillations registered in dense plasma focus experiments were rationalized using the same model with the corresponding kinetic equation converted into the form describing the decaying oscillations caused by exciting force. The model analysis is presented.