NONRECIPROCAL SYNERGISTIC LETHAL INTERACTION BETWEEN 365-nm and 405-nm RADIATION IN WILD TYPE and uvrA STRAINS OF ESCHERICHIA COLI*

Abstract— Lethality by 405-nm radiation in three repair-proficient and two uvrA strains of Escherichia coli that belong to two isogenic series was greatly enhanced by prior exposures to 365-nm radiation at fluences greater than 1 times 10₆Jm_-2. Fluences at 365 nm that yielded a surviving fraction of 0.10 (>1 times 10₆ Jm_-2) in the 5 strains tested resulted in the following 405-nm fluence enhancement factors (FEF, ratio of the 405-nm F₃₇ in the absence of a prior 365-nm irradiation to that in the presence): strain K.12 AB1157 (wild type), 8.7; strain B/r (wild type), 52; strain WP2 (wild type), 25; strain WP2s (uvrA), 13; strain K.12 AB1886 (uvrA), 15. The maximal 405-nm FEF value obtained after a prior 365-nm irradiation at greater fluences was 83 in the wild-type strain B/r. Enhancement of anoxic 405-nm radiation after a prior aerobic 365-nm exposure was not detectable, suggesting that prior aerobic irradiation at 365-nm increased the effects of damage produced at 405 nm by means of an oxygen-dependent process. Single-strand breaks (or alkali-labile bonds) were produced by 405-nm radiation at 3.0 times 10_-5 breaks per 2.5 times 10₉ daltons per Jm_-2 in the polA strain P3478; pyrimidine dimers were not detected by biological assay (photoreactivation) at 405 nm. Although the introduction of different DNA lesions produced by 365- and 405-nm radiations cannot be ruled out, we propose that the strong synergistic effect of 365-nm irradiation on 405-nm lethality is the consequence of pronounced inhibition by 365-nm radiation of components of the DNA-repair systems that can mend or bypass damage produced by 405-nm radiation.     

Bis‐substituted thiophene‐containing oxime sulfonates photoacid generators for cationic polymerization under UV–visible LED irradiation

Three novel types of thiophene‐containing oxime sulfonates with a big π‐conjugated system were reported as non‐ionic photoacid generators. The irradiation of the newly synthesized photoacid generators using near UV–visible light‐emitting diodes (LEDs) (365–475 nm) results in the cleavage of two weak N O bonds in single molecules, which lead to the generation of different sulfonic acids in good quantum and chemical yields. The mechanism for the N O bond cleavage for acid generation was supported by the UV–visible spectra and real‐time ¹H NMR spectra. They are developed as high‐performance photoinitiators without any additives for the cationic polymerization of epoxide and vinyl ether upon exposure to near‐UV and visible LEDs (365–475 nm) at low concentration. In the field of photopolymerization, especially visible light polymerization, it has great potential for application. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 776–782     

光调控的活性自由基聚合的研究新进展

从引发和催化两个方面概述了光辐照在活性自由基聚合(LRP)中的应用,从机理上详细地分析了光辐照对氮氧调控自由基聚合(NMP)、原子转移自由基聚合(ATRP)、可逆加成-断裂链转移自由基聚合(RAFT)以及有机钴催化的可控自由基聚合反应(CMRP)的影响。与传统自由基聚合相比,光调控的活性自由基聚合方法可在温和的条件下生成自由基,能够克服传统LRP的一些缺陷,如降低催化反应活化能、提高聚合物末端官能度等。同时,本文对光调控反应的进一步应用以及新方法的产生也进行了展望。     

Photochemistry and photopolymerization activity of p-nitroaniline in the presence of N,N-dimethylaniline as a bimolecular photoinitiator system

The photoreduction behavior of p-nitroaniline (pNA) in the presence of N,N-dimethylaniline (DMA) induced by both steady-state (365 nm) and laser (337 nm) irradiation has been analyzed. The stoichiometry of the photoreduction reaction revealed that several amino radicals derived from DMA were generated by each photoreduced pNA molecule. The polymerization kinetics of the lauryl acrylate monomer (LA) photoinitiated by the pNA/DMA system has been studied by differential scanning photocalorimetry (Photo-DSC). The rate of polymerization was found to be proportional to the square root of both the incident light and the coinitiator DMA concentration. The order of the polymerization reaction with respect to monomer and initiator concentration was determined, as well as the polymerization behavior under aerobic conditions. The polymerization efficiency of this photoinitiated system was much higher than that obtained with conventional aromatic ketone photoinitiators. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3801–3812, 1997     

PHOTOSENSITIVITY OF Ce (Ⅳ) INITIATED METHYL ACRYLATE POLYMERIZATION

The influences of UV light irradiation (313 nm) and diffused daylight on the polymerization of methyl acrylate initiated by the ceric ammonium nitrate without any reducing agent have been studied both in aqueous nitric acid and in pure water. The rate of polymerization was found to be accelerated and the overall activation energy and the induction time were found to be decreased sharply by the UV light irradiation. Under UV light, the rate of polymerization is 8 times as high as the rate in dark. The rate of polymerization was found to attain a maximum with the increase of nitric acid concentration and the rate of polymerization became less sensitive to UV light in the presence of nitric acid whereas the induction period reduced outstandingly. Based on the experimental results, the mechanism is proposed.     

CORRELATION BETWEEN CELL SURVIVAL AND DNA SINGLE-STRAND BREAK REPAIR PROFICIENCY IN THE CHINESE HAMSTER OVARY CELL LINES AA8 AND EM9 IRRADIATED WITH 365-nm ULTRAVIOLET-A RADIATION

Cell survival parameters and the induction and repair of DNA single-strand breaks were measured in two Chinese hamster ovary cell lines after irradiation with monochromatic UVA radiation of wavelength 365 nm. The radiosensitive mutant cell line EM9 is known to repair ionizing-radiation-induced single-strand breaks (SSB) more slowly than the parent line AA8. EM9 was determined to be 1.7-fold more sensitive to killing by 365-nm radiation than AA8 at the 10% survival level, and EM9 had a smaller shoulder region on the survival curve (alpha = 1.76) than AA8 (alpha = 0.62). No significant differences were found between the cell lines in the initial yields of SSB induced either by gamma-radiation (as determined by alkaline sucrose gradient sedimentation) or by 365-nm UVA (as determined by alkaline elution). For measurement of initial SSB, cells were irradiated at 0.5 degrees C to minimize DNA repair processes. Rejoining of 365-nm induced SSB was measured by irradiating cells at 0.5 degrees C, allowing them to repair at 37 degrees C in full culture medium, and then quantitating the remaining SSB by alkaline elution. The repair of these breaks followed biphasic kinetics in both cell lines. EM9 repaired the breaks more slowly (t1/2 values of 1.3 and 61.3 min) than did AA8 (t1/2 values of 0.9 and 53.3 min), and EM9 also left more breaks unrepaired 90 min after irradiation (24% vs 8% for AA8). Thus, the sensitivity of EM9 to 365-nm radiation correlated with its deficiency in repairing DNA lesions revealed as SSB in alkaline elution.(ABSTRACT TRUNCATED AT 250 WORDS)     

INDUCTION OF DIRECT AND INDIRECT SINGLE-STRAND BREAKS IN HUMAN CELL DNA BY FAR- AND NEAR-ULTRAVIOLET RADIATIONS: ACTION SPECTRUM AND MECHANISMS

Abstract— An action spectrum for the immediate induction in DNA of single-strand breaks (SSBs, frank breaks plus alkali-labile sites) in human P3 teratoma cells in culture by monochromatic 254-, 270-, 290-, 313-, 334-, 365-, and 405-nm radiation is described. The cells were held at +0.5C during irradiation and were Iysed immediately for alkaline sedimentation analysis following the irradiation treatments. Linear fluence responses were observed over the fluence ranges studied for all energies. Irradiation of the cells in a D₂O environment (compared with the normal H₂O environment) did not alter the rate of induction of SSBs by 290-nm radiation, whereas the D₂O environment enhanced the induction of SSBs by 365- and 405-nm irradiation. Analysis of the relative efficiencies for the induction of SSBs, corrected for quantum efficiency and cellular shielding, revealed a spectrum that coincided closely with nucleic acid absorption below 313 nm. At longer wavelengths, the plot of relative efficiency vs . wavelength contained a minor shoulder in the same wavelength region as that observed in a previously obtained action spectrum for stationary phase Bacillus subtilis cells. Far-UV radiation induced few breaks relative to pyrimidine dimers, whereas in the near-UV region of radiation, SSBs account for a significant proportion of the lesions relative to dimers, with a maximum number of SSBs per lethal event occurring at 365-nm radiation.     

Rate mechanisms of a novel thiol-ene photopolymerization reaction

A novel thiol-ene photopolymerization reaction involving copolymerization of tetrathiol monomer with vinyl silazane is experimentally characterized and is modeled successfully. The overall polymerization rate is found to be controlled by the ratio of the propagation to chain transfer kinetic parameters. The polymerization rate of this mixture, in the presence of added photoinitiator, is approximately first order in ene functionality and is independent of thiol functional group concentration. Initiation rates in this system, when cured utilizing a light centered around 365 nm light, and in the presence of no added photoinitiator, are shown to be proportional to the ene monomer concentration. When the mixture is polymerized utilizing light centered at 254 nm light, and without photoinitiator, the initiation rates are proportional to the thiol monomer concentrations. This novel reaction scheme is further utilized to form ultra rapidly polymerizable polymer derived ceramic structures with high aspect ratios.     

Monolayers of diphenyldiacetylene derivatives: Tuning molecular tilt angles and photopolymerization efficiency via electrodeposited Ag interlayer on Au

An electrodeposited Ag adlayer (upd, underpotential deposition) is utilized to improve monolayer photopolymerization of diphenyldiacetylene derivatives (DPDAs) that would otherwise exhibit no polymerization in solid state. Topochemical reaction of diacetylene derivatives via solid-state 1,4-addition yields polydiacetylenes which are of great importance due to properties associated with their ene-yne conjugated backbones. The polymerization efficiency heavily depends on the molecular arrangement in the crystals. For example, crystals of most DPDA derivatives show no activity for topochemical reaction because the bulky phenyl end groups space out the triple bonds and thus DPDAs require relatively large translation and rotation angles for polymerization. In principle, topochemical reaction is viable if molecules are in optimal arrangement. The upd interlayer can be applied to tune the adsorbate-substrate interactions, intermolecular spacing, and the molecular tilt angle by controlling the coverage of the Ag adlayer. It is thus possible to manipulate the molecular arrangement of DPDAs for the subsequent polymerization. Successful photopolymerization of DPDA monolayers is realized from the decrease in nu(C[triple bond]C) intensity by infrared reflectance absorbance spectroscopy, growth of ene-yne pi-pi* transition by UV-vis measurements, and enhanced electrochemical stability by the cathodic desorption protocol. The optimal efficiency of polymerization takes place on upd-modified substrates that can generate approximately 45 degrees tilt angle for DPDA derivatives.     

Unique Curing Properties through Living Polymerization in Crosslinking Materials: Polyurethane Photopolymers from Vinyl Ether Building Blocks

Photopolymers with unique curing capabilities were produced by combining living cationic polymerization with network formation and restricted polymer motion. A vinyl ether diol was synthesized as a functional building block and reacted with isophorone diisocyanate to form a highly functionalized vinyl ether polyurethane as a model system with high crosslinking ability. When using a cationic photoinitiator, fast polymerization is observed upon short UV irradiation. Curing proceeds in the absence of light and under ambient conditions without oxygen inhibition. Cationic active sites become trapped dormant species upon network‐induced vitrification and surprisingly remain living for several days. The polymerization can be reactivated by additional UV irradiation and/or raised temperature. The curing behavior was studied in detail by using UV and FT‐NIR coupled rheology and photo‐DSC to simultaneously study spectroscopic and mechanical information, as well as thermal effects.     

Topochemical polymerization of diphenyldiacetylene-based materials and the relevant application in photocatalysis

Diphenyldiacetylene can be preorganized by self-assembly or external-templating, followed by topochemical polymerization under UV irradiation to form polydiphenyldiacetylene. Such a resulting polymer is a promising photocatalyst for organic pollutant degradation under visible light.     

Light‐Regulated Polymerization under Near‐Infrared/Far‐Red Irradiation Catalyzed by Bacteriochlorophyll a

Photoregulated polymerizations are typically conducted using high‐energy (UV and blue) light, which may lead to undesired side reactions. Furthermore, as the penetration of visible light is rather limited, the range of applications with such wavelengths is likewise limited. We herein report the first living radical polymerization that can be activated and deactivated by irradiation with near‐infrared (NIR) and far‐red light. Bacteriochlorophyll a (Bachl a) was employed as a photoredox catalyst for photoinduced electron transfer/reversible addition–fragmentation chain transfer (PET‐RAFT) polymerization. Well‐defined polymers were thus synthesized within a few hours under NIR (λ=850 nm) and far‐red (λ=780 nm) irradiation with excellent control over the molecular weight (M_n/M_w<1.25). Taking advantage of the good penetration of NIR light, we showed that the polymerization also proceeded smoothly when a translucent barrier was placed between light source and reaction vessel.     

Photochemical cycloaddition reactions of cyanoacetylene and dicyanoacetylene.

Photolysis of cyanoacetylene with 185- or 206-nm light yields 1,3,5-tricyanobenzene while 254-nm radiation yields a mixture of tetracyanocyclooctatetraenes, 1,2,4- and 1,3,5-tricyanobenzene. A polymer of cyanoacetylene is the major photoproduct. 1,3,5-Tricarbomethoxybenzene was the only photoproduct identified from the irradiation of methyl propiolate at 254 nm. Mono-, di-, and tricyanobenzenes are formed by irradiation of mixtures of acetylene and cyanoacetylene at 185, 206, and 254 nm along with trace amounts of cyclooctatetraenes. No photoadducts were detected on photolysis of mixtures of cyanoacetylene and CO or HCN. The tetracyanocyclooctatetraene structures were established by UV, MS, and NMR analyses. The 1H NMR of the product mixture exhibited a singlet at delta 7.028 consistent with either 1 or 2 and two singlets at delta 6.85 and 6.91 assigned to 3. Photolysis of mixtures of dicyanoacetylene and acetylene with either 185- or 206-nm light yielded 1,2-dicyanobenzene and (E,Z)-1-buten-3-yne-1,4-dicarbonitrile. These products were also obtained using 254-nm light along with a mixture of tetracyanocyclooctatetraenes. The same three singlets were observed in this product mixture as were observed in the tetracyanocyclooctatetraenes obtained from cyanoacetylene. From this observation it was concluded that the delta 7.02 signal is due to 2 and not 1. The photolysis of cyanoacetylene and dicyanoacetylene in the presence of ethylene with 185-nm light yields 1-cyanocylobutene and 1,2-dicyanocyclobutene, respectively. 2-Cyanobutadiene and 2,3-dicyanobutadiene are the photoproducts with 254-nm light. Reaction pathways are proposed to explain these findings.     

二硫代酰胺类化合物在盐酸中对碳钢的缓蚀性能(英文)

采用失重实验,动电位极化,交流阻抗,量子化学计算和拉曼光谱等方法研究了N,N′-二异丙氧基丙基二硫代二丙酰胺(DPDA)在1 mol.L-1盐酸溶液中对碳钢的缓蚀性能.失重实验结果表明,DPDA在盐酸溶液中能够有效地抑制碳钢的腐蚀,当缓蚀剂DPDA的浓度为1×10-3 mol.L-1时,其缓蚀效率达到90.2%.极化曲线表明DPDA为混合型缓蚀剂,单一的容抗弧变化表明碳钢电极表面的腐蚀过程主要由电荷转移步骤控制.由失重实验,动电位极化和电化学交流阻抗方法得到的DPDA缓蚀效率具有较好的相关性,均表现为缓蚀效率随着DPDA浓度的增大而增加.另外,DPDA在碳钢表面的吸附符合Langmuir吸附等温式.吸附过程的吉布斯自由能(ΔG0a0d0s)为-38.65 kJ.mol-1,这说明DPDA分子在碳钢表面形成共价键而发生了自发的化学吸附.拉曼光谱表明DPDA分子有效地吸附在碳钢表面,量子化学计算结果证明DPDA分子在碳钢表面的化学吸附活性中心集中在S原子上.     

PHOTOSENSITIVITY OF CERIC ION INITIATED ACRYLAMIDE POLYMERIZATION

Polymerization of acrylamide initiated by ceric ammonium nitrate alone has been studied in aqueous medium. The effects of UV light irradiation on the initial rates of polymerization, the activation energy and on the polymer molecular weights have been investigated. Compared with that in the dark, the rate of polymerization under UV light was accelerated to eleven times higher, and the overall activation energy was lowered markedly.     

Isoquino[4,5-bc]acridines: design, synthesis and evaluation of DNA binding, anti-tumor and DNA photo-damaging ability

Several novel isoquino[4,5-bc]acridine derivatives have been designed and synthesized. Their DNA-binding, anti-tumor and DNA-photo-damaging properties were investigated. A4 exhibited the highest anti-tumor activities against both A 549 (human lung cancer cell) and P388 (murine leukemia cells). All these compounds were found to be more cytotoxic against P388 than against A549. Under 365-nm light irradiation, A3 damaged plasmid DNA pBR322 at <2 microM and cleaved DNA from form I to 100% form II by 50 microM. The mechanism studies revealed that A3 damaged DNA by electron transfer mechanism and singlet oxygen species.     

铽-氟罗沙星配合物光化学荧光增强研究

铽 氟罗沙星 (FLRX)配合物在 36 5nm紫外光照射一定时间后 ,Tb3 的特征荧光强度大大提高。通过对该体系的荧光光谱、磷光光谱、荧光量子效率和荧光寿命等的测定 ,证实Tb3 FLRX配合物光照后发生了光化学反应 ,形成了更有利于分子内能量传递的Tb3 配合物。探讨了其荧光增敏机制。     

Observations on photochemical fluorescence enhancement of the terbium(III)-sparfloxacin system.

Fluorescence of terbium(III) was sensitized when excited in the presence of sparfloxacin (SPFX) in the aqueous solution because a Tb(III)-SPFX complex was formed. The sensitized fluorescence was further enhanced when this system was exposed to 365 nm ultraviolet light. By the spectral properties and contrast experiments, it is proved that irradiation makes this system undergo photochemical reactions and a new terbium complex which is more favorable to the intramolecular energy transfer is formed. The mechanism of photochemical fluorescence enhancement of the Tb(III)-SPFX system is discussed and a new sensitive and selective photochemical fluorimetry for the determination of SPFX is established. Under the optimum conditions, the linear range is 1.0-50 x 10(-7) M for SPFX, the detection limit is 3.0 x 10(-9) M and the R.S.D. for 5.0 x 10(-7) M SPFX is 1.3% (n = 9). Without any pretreatment the recovery of SPFX in human urine was determined with satisfaction.     

DNA BREAKS CAUSED BY MONOCHROMATIC 365 nm ULTRAVIOLET-A RADIATION OR HYDROGEN PEROXIDE and THEIR REPAIR IN HUMAN EPITHELIOID and XERODERMA PIGMENTOSUM CELLS

The induction and repair of DNA single-strand breaks (SSB) assayed by alkaline filter elution was compared in human epithelioid P3 and xeroderma pigmentosum (XP) cells exposed to monochromatic 365-nm UV-A radiation and H2O2. Initial yields of SSB were measured with the cells held at 0.5 degrees C during exposure. The yield from exposure to 365-nm radiation was slightly greater in XP than in P3 cells, whereas H2O2 produced more than three times as many SSB in P3 compared with XP cells. o-Phenanthroline (50 mM) markedly inhibited the yields of SSB induced in XP cells by H2O2, but had no effect on those produced by 365-nm UV-A. These results are consistent with the fact that P3 cells, unlike XP cells, have undetectable levels of catalase. The measured production of trace amounts of H2O2 by the actual 365-nm UV-A exposures was not sufficient to account for the numbers of breaks that were observed. Single-strand breaks produced by both agents were completely repaired after 50 min in P3 cells, as were H2O2-induced SSB in XP cells. However, 25% of the 365-nm UV-A-induced SSB in XP cells remained refractory to repair after 60 min. The results show that SSB produced by these two agents are different and that 365 nm radiation produces most SSB in cells by mechanisms other than by production of H2O2.     

From UV to NIR: A Full-Spectrum Metal-Free Photocatalyst for Efficient Polymer Synthesis in Aqueous Conditions

Photo-mediation offers unparalleled spatiotemporal control over controlled radical polymerizations (CRP). Photo-induced electron/energy transfer reversible addition–fragmentation chain transfer (PET-RAFT) polymerization is particularly versatile owing to its oxygen tolerance and wide range of compatible photocatalysts. In recent years, broadband- and near-infrared (NIR)-mediated polymerizations have been of particular interest owing to their potential for solar-driven chemistry and biomedical applications. In this work, we present the first example of a novel photocatalyst for both full broadband- and NIR-mediated CRP in aqueous conditions. Well-defined polymers were synthesized in water under blue, green, red, and NIR light irradiation. Exploiting the oxygen tolerant and aqueous nature of our system, we also report PET-RAFT polymerization at the microliter scale in a mammalian cell culture medium.