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.     

SENSITIVITY OF STRAINS OF ESCHERICHIA COLI DIFFERING IN REPAIR CAPABILITY TO FAR UV,NEAR UV AND VISIBLE RADIATIONS*

Abstract— In stationary phase, strains of Escherichia coli deficient in excision (B/r Her) or recombination repair (K.12 AB2463) were more sensitive than a repair proficient strain (B/r) to monochromatic near-ultraviolet (365 nm) and visible (460 nm) radiations. The relative increase in sensitivity of mutants deficient in excision or recombination repair, in comparision to the wildtype, was less at 365 nm than at 254 nm. However, a strain deficient in both excision and recombination repair (K12 AB2480) showed a large, almost equal, increase in sensitivity over mutants deficient in either excision or recombination repair at 365 nm and 254 nm. All strains tested were highly resistant to 650 nm radiation. Action spectra for lethality of strains B/r and B/r Her in stationary phase reveal small peaks or shoulders in the 330–340, 400–410 and 490–510 nm wavelength ranges. The presence of 5μg/ml acriflavine (an inhibitor of repair) in the plating medium greatly increased the sensitivity of strain B/r to radiation at 254, 365 and 460 nm, while strains E. coli B/r Her and K12 AB2463 were sensitized by small amounts. At each of the wavelengths tested, acriflavine in the plating medium had at most a small effect on E. coli K.12 AB2480. Acriflavine failed to sensitize any strain tested at 650 nm. Evidence supports the interpretation that lesions induced in DNA by 365 nm and 460 nm radiations play the major role in the inactivation of E. coli by these wavelengths. Single-strand breaks (or alkali-labile bonds), but not pyrimidine dimers are candidates for the lethal DNA lesions in uvrA and repair proficient strains. At high fluences lethality may be enhanced by damage to the excision and recombination repair systems.     

WAVELENGTH-DEPENDENT EFFECTS OF BENZOPORPHYRIN DERIVATIVE MONOACID RING A in vivo AND in vitro

Abstract Benzoporphyrin derivative monoacid ring A (BPD-MA) is a chlorin-like photosensitizer currently in clinical trials for cancer and psoriasis. It has maximal absorption peaks at both 630 and 690 nm and can be activated at both these wavelengths. In vitro phototoxicity tests using the P8 15 murine mastocytoma cell lines conducted over wavelengths of light between 678 and 700 nm emitted by an argon-ion pumped dye laser showed that equivalent cell kill could be achieved between 682 and 690 nm. Tests on in vivo phototoxicity of normal skin of DBN2 mice injected with 2 mg/kg of BPD-MA and exposed to light at 125 J/cm², between 620 and 700 nm, demonstrated peaks of normal skin damage occurring at 630–640 nm and 680–690 nm. In tests carried out with light between 620 and 700 nm, at 10 nm increments, it was seen that light delivered at 680–690 nm caused slightly more damage to normal skin than light delivered at 630–640 nm. When lower doses of light between 675 and 705 nm were tested using smaller increments, it was determined that equivalent skin damage occurred over a range of 68–95 nm. Antitumor efficacy in tumor-bearing DBN2 mice was tested between 683 and 695 nm. It was found that equivalent antitumor efficacy, determined by assessing tumor-free status at 20 days posttreatment, occurred at wavelengths between 685 and 693 nm. When tumor-bearing animals injected with BPD-MA at 2 mdkg and exposed to light 3 h later were treated with either 630 or 690 nm light at various doses, it was observed that 690 nm light was more effective at tumor ablation than was 630 nm light, demonstrating that while similar damage to normal skin may be effected by equivalent doses of light at either wavelength, tumor ablation was greater at 690 nm. Further, our data suggest that alternative light sources with bandwidths greater than those of the argon-ion pumped dye laser (±0.3 nm) may have equivalent efficacy with this photosensitizer.     

ACTION SPECTRA FOR HYPHAL AGGREGATION,THE FIRST STAGE OF FRUITING,IN THE BASIDIOMYCETE Pleurotus ostreatus*

Abstract. Action spectra were determined for hyphal aggregation in Pleurotus ostreatus at wavelengths between 360 and 600 nm. The action spectrum for a 50% response had two maxima, one at 370 nm in the near-UV and the other a broad peak at 440–450 nm in the blue. Both were approximately of the same magnitude. A minimum was present at 400 nm and wavelengths greater than 530 nm invoked no response. Action spectra for a range of responses, 10–90%, were also determined which showed gradual changes in the peaks in the blue region. It was concluded that hyphal aggregation in P. ostreatus is under the control of a cryptochrome-like photoreceptor system.     

AN ACTION SPECTRUM IN THE BLUE and ULTRAVIOLET FOR PHOTOTROPISM IN ALFALFA*

Abstract Phototropism is a common property of plants, but it is not known if different species use the same photoreceptor for their response. We have determined fluence-response relations for phototropism in response to brief, broad-band blue irradiation for four plant species grown under red light (Amaranthus paniculatus, Linum usitatissimum, Vigna radiata and Medicago sativa) and compared these to ones previously obtained for Pisum sativum and Zea mays, grown under similar conditions. Curves for all species showed a bell-shaped dependence on fluence, a characteristic of first positive curvature as originally defined for the Avena coleoptile, and had a similar optimal fluence, near 3 H.mol m^?2. We have obtained an action spectrum in the blue and UV spectral regions for first positive phototropism of the hypocotyl of alfalfa grown under red light. Fluence-response curves at wavelengths between 300 and 500 nm were nearly identical in shape and magnitude; whereas below 300 nm, their slopes and maximum curvatures were reduced. The action spectrum showed that activity rose sharply at wavelengths below 500 nm, peaked at 450 nm with shoulders on either side of that peak, and had lesser peaks at 380 and, in the far ultraviolet, at 280 nm. This action spectrum was very similar to ones in the literature (obtained between 350 and 500 nm) for first and second positive phototropism of oat coleoptiles. We conclude that the same photoreceptor mediates phototropism in oat and alfalfa.     

QUANTUM YIELD RATIO OF THE FORWARD and BACK LIGHT REACTIONS OF BACTERIORHODOPSIN T LOW TEMPERATURE and PHOTOSTEADY-STATE CONCENTRATION OF THE BATHOPRODUCT K*

The maximum photosteady state fraction of K, x_K^max, and the ratio of the quantum yields of the forward and back light reactions, trans-bacteriorhodopsin (bR) hArr; K, φ_bR/φ_K, were obtained by measuring the absorption changes produced by illumination of frozen water-glycerol (1:2) suspensions of light-adapted purple membrane at different wavelengths at -165°C. An independent method based on the second derivative of the absorption spectrum in the region of the β-bands was also used. It was found that The quantum yield ratio (0.66 ± 0.06) was found to be independent of excitation wavelength within experimental error in the range510–610 nm. The calculated absorption spectrum of K has its maximum at603–606 nm and an extinction 0.85 ± 0.03 that of bR. At shorter wavelengths there are P-bands at 410, 354 and 336 rim. Using the data of Hurley et al. (Nature 270,540–542, 1977) on relative rates of rhodopsin bleaching and K formation, the quantum yield of K formation was determined to be 0.66 ± 0.04 at low temperature. The quantum efficiency of the back reaction was estimated to be 0.93 ± 0.07. These values of quantum efficiencies of the forward and back light reactions of bR at - 165°C coincide with those recently obtained at room temperature. This indicates that the quantum efficiencies of both forward and back light reactions of bacteriorhodopsin are temperature independent down to -165°C.     

Study on side-chain second-order nonlinear optical polyimides based on novel chromophore-containing diamines. I. Synthesis and characterization

Side-chain second-order nonlinear optical polyimides were prepared from four novel chromophore-containing diamines and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride by a traditional two-step process that included a solution polycondensation followed by a chemical imidization. The four diamines were 2,4-di-β-aminoethylamino-6-p-nitrophenylamino-1,3,5-triazine (M1), 4-nitro-4′-[N-(4,6-di-β-aminoethylamino)-1,3,5-triazin-2-yl]amino azobenzene (M2), 2,4-di-p-aminophenylamino-6-p-nitrophenylamino-1,3,5-triazine (M3), and 4-nitro-4′-[N-(4,6- di-4-aminophenylamino)-1,3,5-triazin-2-yl]amino azobenzene (M4). All the polyimides exhibited maximum ultraviolet-visible absorption peaks or shoulders of chromophores at wavelengths below 400 nm, and those based on M1 and M3 were transparent at wavelengths above 450 nm, whereas those based on M2 and M4 were transparent at wavelengths above 550 nm. The polyimides possessed high glass-transition temperatures (T_g's; 218–247 °C) and thermal decomposition temperatures. They were soluble in aprotic solvents such as N-methyl-2-pyrrolidone, N,N-dimethyl acetamide, N,N-dimethyl formamide, and dimethylsulfone. Some were even soluble in common low-boiling-point solvents such as tetrahydrofuran. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4330–4336, 1999     

Syntheses and photophysical properties of fluorescent dibenzofurans,a dibenzothiophene,and carbazoles substituted with benzoxazole and hydroxyl groups to produce excited state intramolecular proton-transfer

Dibenzofurans, a dibenzothiophene, and carbazoles, each substituted with a 2-benzoxazolyl group as well as an ortho-hydroxyl group, were synthesized to produce fluors with fluorescence due to excited-state intramolecular proton-transfer. The orientations for Friedel-Crafts acylation of 3-methoxydibenzothio-phene and of the analogous carbazole were determined. The fluors displayed absorption peaks in the 330–385 nm region with molar extinction coefficients up to 57,000. Fluorescence quantum efficiencies of 0.17–0.44 were obtained at wavelengths that had peak values from 540–600 nm. The fluors are of potential use as wavelength shifters in scintillating polystyrene fibers.     

Nitrate and Nitrite Ultraviolet Actinometers

Abstract We developed nitrate and nitrite actinometers to determine radiant fluxes from 290 to 410 nm. These actinometers are based on the reaction of the photochemically generated OH radical with benzoic acid to form salicylic acid (SA) and p-hydroxybenzoic acid (pHBA). Actinom-eter development included determination of the temperature and wavelength dependence of the quantum yield for formation of SA and pHBA from nitrate and nitrite photolysis in air-saturated solutions. Quantum yields (at 25°C) for SA production from nitrate photolysis ranged from 0.00146 to 0.00418 between 290 and 350 nm, and from 0.00185 to 0.00633 for nitrite photolysis between 290 and 405 nm. The quantum yields for SA production were approximately 50–60% greater than quantum yields for pHBA production from nitrate and nitrite photolysis. For both actinometers, SA and pHBA formation was temperature dependent, increasing by approximately a factor of 2.2 from 0 to 35°C. Activation energies for SA formation varied with wavelength, ranging from 14.7 to 16.5 kj mol -¹ between 290 and 330 nm for the nitrate actinometer and 12.3 to 17.8 kj mol-¹ between 310 and 390 nm for the nitrite actinometer. Activation energies for pHBA formation were 2–11% higher. Wavelength-dependent changes in the quantum yield and activation energy for SA and pHBA formation from nitrate photolysis suggest multiple electronic transitions for nitrate from 290 to 350 nm. Quantum yields for OH radical formation from nitrate and nitrite photolyses were estimated from SA and pHBA quantum yields at 25°C. Wavelength-dependent OH quantum yields ranged from 0.007 to 0.014 for nitrate photolysis between 290 and 330 nm and from 0.024 to 0.078 for nitrite photolysis between 298 and 390 nm. The nitrate and nitrite actinometers can maintain initial rate conditions for hours, are insensitive to laboratory lighting, easy to use and extremely sensitive; the minimum radiant energy that can be detected in our irradiation system is approximately 10^-9 einsteins.     

Photooxidation of PVC

Pure and peroxided PVC films were irradiated under monochromatic ultraviolet light between 300 and 400 nm. The degradation state of PVC is measured by means of carbonyl absorption in the infrared spectra and polyene content by UV spectroscopy. The initial rate of carbonyl formation depends on the wavelengths and oxidized impurities content. Peroxided PVC is oxidized faster than pure PVC with wavelengths above 320 nm. Two hazardous ranges of wavelengths have been detected: 300–320 and 350–370 nm. Good protection of PVC against UV radiation can be assured by the exclusion of wavelengths under 380 nm.     

Growth Dynamics Study of Silver Nanoparticles Obtained by Green Synthesis using Salvia officinalis Extract

ABSTRACT

Silver nanoparticles were synthesized by the bottom-up approach using Salvia officinalis extract, and their growth process was correlated with changes in their ultraviolet–visible spectra. Experiments were performed at different initial mixing ratios of silver nitrate to plant extract and at pH values to outline a pattern concerning the growth of silver nanoparticles obtained by this synthesis procedure. Relative areas calculated from the spectra from 350 to 600?nm were used as a comparison for the growth dynamics of silver nanoparticles synthesized in mixtures with different compositions. The graphical representation of relative areas vs. time presents four stages of nanoparticle growth with each linear portion corresponding to a different process rate.     

Synthese von 2H-Isoindol-4,7 -dionen durch photochemische Cycloaddition von 2,3-Diphenyl-2H-azirin an 1,4-Chinone. 38. Mitteilung über Photoreaktionen

2, 3-Diphenyl-2H-azirine ( 1 ) reacts on irradiation with light of wavelength 290–350 nm with 1,4-benzoquinones 3–6 or with 1,4-naphthoquinones 7–9 forming the yellow to red coloured 1,3-diphenyl-2H-isoindole-4, 7-diones 10–13 (33–43% yield) resp. 1, 3-diphenyl-2H-benzo[f]isoindole-4,9-diones 14–16 (33–36% yield) (Scheme 1). The structures of these hitherto unknown products follow from the analytical and spectral data. The probable formation of the isoindole-diones is depicted in Scheme 2. The intermediate benzonitrile-benzylide ( 2 ), which most certainly arises, adds onto the unsubstituted C, C-double bond of the quinones and not onto the C,O-double bonds. On exclusion of atmospheric oxygen there results from 1 and 2-methyl-1, 4-benzoquinone ( 4 ) a product (probably b ) which hardly absorbs in the region 350–450 nm. The latter, with the agency of atmospheric oxygen (but not 4 ), is converted into 5-methyl-1, 3-diphenyl-2H-isoindole-4, 7-dione ( 11 ). The relative slowness of this oxidation (see Fig. 2) enables an almost complete photochemical transformation of the azirine 1 , which only weakly absorbs above 290 nm. Otherwise 11 , which strongly absorbs above 290 nm, would hinder the photolysis of 1 .     

SURVIVAL, SPORE FORMATION AND EXCISION REPAIR OF UV-IRRADIATED DEVELOPING CELLS OF DICTYOSTELIUM DISCOIDEUM NC-4

Abstract— The synchronously developing aggregates of the cellular slime mold, Dictyostelium discoideum NC-4, were disaggregated into individual cells and irradiated with 254 nm UV light at preaggregation (0h), late interphase (6h), late aggregation (12 h), and preculmination (18 h). When assayed for replica-tive ability (colony formation), the developing cells at 0, 6, 12, and 18h showed the same sensitivity as vegetative cells; the 10% survival dose (D₁₀) was 160 J/m². The spores were more sensitive, with D₁₀ of 70 J/m². Excision repair of the nuclear DNA of the developing cells was studied by alkaline sucrose gradients. UV-induced single-strand breakage and rejoining of the DNA occurred to the same final extent in the cells from the 0, 6, 12 and 18 h stages of development, but a longer time was required for the completion of rejoining at the later stages (for example, at 54 J/m², 6.6 h for preculmination cells, 3.3 h for preaggregation cells). When the cells irradiated at various stages were required to redevelop, as measured by the relative numbers of spores produced, their sensitivity for completing this development increased the later the stage from which they were taken. The D₁₀s for spore production were 200, 130, 100 and 70 J/m² for cells at the 0, 6, 12 and 18 h stages, respectively. The fractional viability among the spores that appeared after this treatment was the same independent of the stage at which the cells were irradiated; the D₁₀ for this viability was 160 J/m², the same as if the cells had been plated immediately with no intervening developmental sequence. We conclude that DNA excision repair as related to replicative ability is retained at all stages of development; however, development seems independent of replicative ability and depends upon DNA and/or non-DNA damage in a more complex way.     

Optimal Technological Parameters of Diesel Fuel Hydroisomerization Unit Work Investigation by Means of Mathematical Modelling Method

Mathematical model of diesel fuel hydroisomerization has been developed on the base of the system analysis strategy, which consists of the sequence of the following stages: thermodynamic analysis of chemical reactions possibility, the hydrocarbons conversion scheme drafting, kinetic model development, kinetic parameters estimation by means of inverse kinetic problem solution and large massive of full-scale experimental data and model verification to the real process. Using the developed model, the hydroisomerization process kinetic regularities have been investigated, the temperature influence in the range of 350–410^oC, pressure influence within 4.3-9.3 MPa, hydrogen containing gas flow rate influence in the range of 5000–53000 m³/h while the feed flow rate is 301 m³/h on the product composition have been studied. An optimal technological regime has been determined.     

Shape‐controlled synthesis of Pt nanocrystals: an evolution of the tetrahedral shape

Platinum nanocrystals with sizes smaller than 10 nm are obtained by H₂‐reduction of aqueous K₂PtCl₆ in the presence of different concentrations of poly (N‐vinyl‐2‐pyrrolidone; PVP:M_w ≈ 360 000) at pH = 2.5–7.0. Tetrahedral Pt nanocrystals (3–10 nm) are produced with high selectivity (73–83% by number) at moderate PVP:K₂PtCl₆ ratios. The co‐existing round/spheroidal crystallites are found to be smaller than the tetrahedrally shaped ones in the systems of varying K₂PtCl₆:PVP ratios. Careful examinations of the particle size and shape evolution of the crystallites at different stages of the crystal growth with transmission electron microscopy (TEM) and ultraviolet–visible absorption spectroscopy (UV–vis) suggest that the tetradedrally shaped Pt crystallites share the same type of nuclei with the round ones at the early stage of the crystal formation. Evolution of the tetrahedral shape happens in the later slow crystal growth. Copyright © 2006 John Wiley & Sons, Ltd.     

Thermal decomposition of RDX/AP by TG–DSC–MS–FTIR

The method of TG–DSC–MS–FTIR simultaneous analysis has been used to study the thermal decomposition mechanism of the RDX/AP (1/2) mixture. TG–DSC showed that there were two mass loss processes for thermal decomposition of RDX/AP. The first one was mainly ascribed to the thermal decomposition of RDX. Addition of AP to RDX causes decomposition to take place abruptly, after melting, resulting in a very sharp and strong peak at lower temperature. The apparent activation energies, calculated by model-free Friedman method, of this process were negative. The second mass loss process of RDX/AP was confirmed to be the thermal decomposition of AP, catalyzed by RDX. This process can be divided into three stages, which were an nth-order autocatalytic and two one-dimensional diffusion stages, respectively. There was a competition among the formation reactions of N₂O, HNCO, and HCl for the first stage and between NO₂ and N₂O for the later two stages. The production of N₂O dominated in the second stage, while NO₂ did in the third stage.     

ACTION SPECTRA FOR LETHALITY IN RECOMBINATION-LESS STRAINS OF SALMONELLA TYPHIMURIUM AND ESCHERICHIA COLI*

Abstract— Action spectra for lethality of both stationary and exponentially growing cells of recombinationless (recA) mutants of Salmonella typhimurium and Escherichia coli were obtained. Maximum sensitivity was observed at 260nm which corresponds to the maximum absorbance of DNA. However, a shoulder occurred in the 280–300 nm range that departed significantly from the absorption spectrum of DNA. At wavelengths longer than 320nm, the shapes of inactivation curves departed significantly from those at wavelengths shorter than 320nm and survival curves at wavelengths longer than 320nm had a large shoulder. A small peak or shoulder occurred in the 330–340nm region of the action spectra. The special sensitivity of recA mutants to broad spectrum near-UV radiation may be due to synergistic effects of different wavelengths. Parallels between the inactivation of recA mutants and the induction of a photoproduct of l -tryptophan toxic for recA mutants (now known to be H₂O₂) suggest that H₂O₂ photoproduct from endogenous tryptophan may be involved in the high sensitivity of these strains to broad spectrum near-UV radiation.     

Evidence for a pterin-derivative associated with the molybdenum cofactor of Neurospora crassa nitrate reductase

Abstract— Following the method of Johnson and Rajagopalan (1982) for obtaining Form B of molybdopterin cofactors, we observed a prominent fluorescence band at480–482 nm in purified NR of Neurospora crassa mutant albino-band after boiling the enzyme at acidic pH and readjusting the sample to alkaline pH. This fluorescence band is maximally excited at 410 nm and maximally emitting at pH 11 (“F-480_pH11”); at pH4–7 only a featureless fluorescence band of low intensity remains (“F-480_pH5”). The fluorescence ΔF-480 = F-480_pH11 - F-480_pHS is examined here. ΔF-480 is associated specifically with NADPH-dependent and MVH-dependent nitrate reduction activities and with cytochrome b-557 absorption. In a protease-digested preparation lacking NADPH-dependent NR activity, ΔF-480 is associated with MVH-dependent nitrate reduction. The ΔF-480 signal is followed during the course of purification of NR. Its size increases with increasing purity of the enzyme. In partially purified NR preparations and especially in aqueous extracts from mycelia of N. crassa, a second, strong fluorescence signal with a pH-dependent emission maximum at around 450 nm (maximally excited at350–370 nm) was found beside ΔF-480. This “unspecific” signal was lost during NR purification. A procedure is developed to demonstrate AF-480 also in presence of the unspecific (350-370/450 nm) signal as well as flavins. We deduce that the ΔF-480 component is part of the Mo cofactor of N. crassa NR and that the signal is caused by a pterin derivative. From calculations of total content of the AF-480 component in mycelia it is likely that in vivo it is shared also by other enzymes.     

Synthesis and properties of polyacetylenes with salicylideneaniline groups

Acetylenes containing salicylideneaniline groups—N‐salicylidene‐3‐ethynylaniline ( 1 ), N‐(3‐t‐butylsalicylidene)‐3‐ethynylaniline ( 2 ), and N‐(3‐t‐butylsalicylidene)‐4‐ethynylaniline ( 3 )—polymerized smoothly and gave yellow to red polymers in excellent yields when a rhodium catalyst was employed. Polymers with alkyl substituents on the aromatic rings [poly( 2 ) and poly( 3 )] were soluble in CHCl₃, tetrahydrofuran, and so forth, whereas the polymer without alkyl substituents [poly( 1 )] was insoluble in any solvent. N‐(3‐t‐Butylsalicylidene)propargylamine did not provide any polymer. Thermogravimetric analyses of the resultant polymers exhibited good thermal stability (T_o, onset temperature of weight loss > 300 °C). The ultraviolet–visible spectra of the polymers showed absorption maxima and cutoff wavelengths around 360 and 520 nm, respectively. The polymers exhibited largely Stokes‐shifted fluorescence (emission wavelength ? 550 nm) upon photoexcitation at 350 nm, which resulted from the photoinduced intramolecular proton transfer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2458–2463, 2002     

Deep-UV Raman spectrometer tunable between 193 and 205 nm for structural characterization of proteins

A new deep-UV Raman spectrometer utilizing a laser source tunable between 193 and 205 nm has been designed, built, and characterized. Only selected wavelengths from this range have previously been accessible, by Raman shifting of the second, third, and fourth harmonics of the Nd:YAG fundamental in hydrogen. The apparatus was demonstrated to be a useful tool for characterizing hen egg white lysozyme structural rearrangements at various stages of fibril formation. High-quality deep-UV resonance Raman spectra were obtained for both a protein solution and a highly-scattering gelatinous phase formed by fibrillogenic species. In addition to amide bands, strong contribution of ₁₂ and ring-C phenylalanine vibrational modes was observed at excitation wavelengths below 200 nm. Remarkably, the Raman cross-section of these modes revealed dramatic change of lysozyme in response to heat denaturation and fibril formation. These results indicate that phenylalanine could serve as a new deep-UV Raman probe of protein structure.