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Journal of Agricultural and Food... Apr 2017Imazosulfuron, a sulfonylurea herbicide used in rice cultivation, has been shown to undergo photodegradation in water, but neither the photochemical mechanism nor the... (Comparative Study)
Comparative Study
Imazosulfuron, a sulfonylurea herbicide used in rice cultivation, has been shown to undergo photodegradation in water, but neither the photochemical mechanism nor the role of indirect photolysis is known. The purpose of this study was to investigate the underlying processes that operate on imazosulfuron during aqueous photodegradation. Our data indicate that in the presence of oxygen, most photochemical degradation proceeds through a direct singlet-excited state pathway, whereas triplet-excited state imazosulfuron enhanced decay rates under low dissolved oxygen conditions. Oxidation by hydroxyl radical and singlet oxygen were not significant. At dissolved organic matter (DOM) concentrations representative of rice field conditions, fulvic acid solutions exhibited faster degradation than rice field water containing both humic and fulvic acid fractions. Both enhancement, via reaction with triplet-state DOM, and inhibition, via competition for photons, of degradation was observed in DOM solutions.
Topics: Herbicides; Hydroxyl Radical; Kinetics; Oxidation-Reduction; Photolysis; Pyridines; Pyrimidines
PubMed: 28368590
DOI: 10.1021/acs.jafc.7b00134 -
Macromolecular Rapid Communications Jul 2018Photocleavable polymers have attracted much attention in drug delivery, photopatterning, and controlling cell behavior. Photolysis is usually induced by UV light.... (Review)
Review
Photocleavable polymers have attracted much attention in drug delivery, photopatterning, and controlling cell behavior. Photolysis is usually induced by UV light. However, UV light cannot penetrate deeply into biological tissue and may damage biological components. Therefore, conventional UV-light-cleavable polymers are problematic for deep-tissue biomedical applications. In this feature article, red and near-infrared light-cleavable polymers are reviewed, and their potential applications are highlighted. The remaining challenges in the field of photocleavable polymers are discussed.
Topics: Drug Delivery Systems; Humans; Infrared Rays; Light; Nanoparticles; Photolysis; Polymers
PubMed: 29682838
DOI: 10.1002/marc.201800034 -
Faraday Discussions Oct 2019We describe cyclic peptide progelators which cleave in response to UV light to generate linearized peptides which then self-assemble into gel networks. Cyclic peptide...
We describe cyclic peptide progelators which cleave in response to UV light to generate linearized peptides which then self-assemble into gel networks. Cyclic peptide progelators were synthesized, where the peptides were sterically constrained, but upon UV irradiation, predictable cleavage products were generated. Amino acid sequences and formulation conditions were altered to tune the mechanical properties of the resulting gels. Characterization of the resulting morphologies and chemistry was achieved through liquid phase and standard TEM methods, combined with matrix assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS).
Topics: Biocompatible Materials; Bioprinting; Gels; Peptides, Cyclic; Photolysis; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Ultraviolet Rays
PubMed: 31549115
DOI: 10.1039/c9fd00026g -
The Journal of Organic Chemistry Jul 2023The photolysis of 2-azidofluorene in solid argon at 3 K results in the formation of 2-fluorenylnitrene. The nitrene undergoes subsequent rearrangements to two isomeric... (Review)
Review
The photolysis of 2-azidofluorene in solid argon at 3 K results in the formation of 2-fluorenylnitrene. The nitrene undergoes subsequent rearrangements to two isomeric didehydroazepines (ketenimines) which differ in the position of the N atom in the seven-membered ring. The rearrangement of the nitrene to the didehydroazepines proceeds in a two-step process. The first step is a photochemical rearrangement to form the corresponding isomeric benzazirines and . The second step is the opening of the three-membered rings of and to form the isomeric didehydroazepines. While benzazirine could easily be detected, isomer was not observed, despite the corresponding didehydroazepine being formed in the matrix. Further experiments revealed that rearranges to the didehydroazepine via heavy-atom tunneling. Semiquantitative estimations based on DFT calculations confirm that should undergo a tunneling rearrangement with tunneling rates on the order of the experimentally observed rates. In contrast, estimations for suggest that for this isomer the tunneling rates should be much larger, resulting in lifetimes too short to be observable under the conditions of matrix isolation. These experiments demonstrate the influence of position isomerism on quantum tunneling rates.
Topics: Isomerism; Imines; Photolysis
PubMed: 37204141
DOI: 10.1021/acs.joc.3c00484 -
Chemical Communications (Cambridge,... Feb 2023Chemical labeling of proteins in live cells helps to probe their native functions in biological systems. Aryl azides are chemically inert under physiological conditions,... (Review)
Review
Chemical labeling of proteins in live cells helps to probe their native functions in biological systems. Aryl azides are chemically inert under physiological conditions, but they are activated by certain external stimuli. Recently, photocatalytic live-cell applications of aryl azides by visible light irradiation have become a burgeoning new field in chemical biology. In this Feature Article, we focus on the recent progress of protein labeling in live cells with aryl azides induced by visible-light irradiation. Light irradiation activates aryl azides to generate highly reactive intermediates, which enables protein labeling for protein functionalization, crosslinking, and profiling. The activation mechanism of aryl azides by light irradiation is categorized as photolysis, energy-transfer, and electron-transfer. The extracellular and intracellular protein labeling applications in live cells with aryl azides induced by visible light are discussed, including recent advances in red-light-induced extracellular protein labeling.
Topics: Azides; Light; Photolysis; Energy Transfer
PubMed: 36744609
DOI: 10.1039/d2cc06987c -
Environmental Science & Technology Apr 2018Aqueous methylglyoxal chemistry has often been implicated as an important source of oligomers in atmospheric aerosol. Here we report on chemical analysis of brown carbon...
Aqueous methylglyoxal chemistry has often been implicated as an important source of oligomers in atmospheric aerosol. Here we report on chemical analysis of brown carbon aerosol particles collected from cloud cycling/photolysis chamber experiments, where gaseous methylglyoxal and methylamine interacted with glycine, ammonium, or methylammonium sulfate seed particles. Eighteen N-containing oligomers were identified in the particulate phase by liquid chromatography/diode array detection/electrospray ionization high-resolution quadrupole time-of-flight mass spectrometry. Chemical formulas were determined and, for 6 major oligomer products, MS fragmentation spectra were used to propose tentative structures and mechanisms. Electronic absorption spectra were calculated for six tentative product structures by an ab initio second order algebraic-diagrammatic-construction/density functional theory approach. For five structures, matching calculated and measured absorption spectra suggest that they are dominant light-absorbing species at their chromatographic retention times. Detected oligomers incorporated methylglyoxal and amines, as expected, but also pyruvic acid, hydroxyacetone, and significant quantities of acetaldehyde. The finding that ∼80% (by mass) of detected oligomers contained acetaldehyde, a methylglyoxal photolysis product, suggests that daytime methylglyoxal oligomer formation is dominated by radical addition mechanisms involving CHCO*. These mechanisms are evidently responsible for enhanced browning observed during photolytic cloud events.
Topics: Aerosols; Gas Chromatography-Mass Spectrometry; Nitrogen; Photolysis; Pyruvaldehyde
PubMed: 29510022
DOI: 10.1021/acs.est.7b06105 -
Journal of Biochemical and Biophysical... Nov 1984A wide variety of biologically relevant chemical intermediates have been identified and characterised by their spectral properties. When rapid kinetics, i.e. rapid...
A wide variety of biologically relevant chemical intermediates have been identified and characterised by their spectral properties. When rapid kinetics, i.e. rapid changes in these spectral properties are studied, the equipment designed for these studies (flash photolysis-, T-jump apparatus) usually allows only the registration of intensity changes of the monitoring light beam at one particular wavelength. Quite frequently, however, particularly in biological systems, the reactions of interest are too complex to be fully understood using single wavelength techniques. We have therefore designed and built a flash photolysis apparatus which permits the simultaneous recording of absorbance changes at 32 wavelengths, freely selectable between 300 and 1000 nm, as well as changes in fluorescence, luminescence, birefringence and light scattering. The apparatus, which we have called Polychromatic Flash Photolysis Apparatus (PFPA), acquires up to 8000 difference spectra per second with an amplitude resolution of better than 0.0001 absorbance unit. Data acquisition and activation of an actinic xenon flash unit occurs under computer control. The same computer is responsible for data storage, handling and graphic display. This communication describes the PFPA, its performance, and, as a demonstration of its potential usefulness, its application to the measurement of the light driven photocycle of bacterial rhodopsin, the proton pumping protein of Halobacterium halobium.
Topics: Photolysis; Scattering, Radiation; Spectrophotometry
PubMed: 6520324
DOI: 10.1016/0165-022x(84)90048-4 -
Photochemistry and Photobiology Nov 2021An overview of the history, mechanistic aspects and applications is provided for p-hydroxyphenacyl (pHP) and benzoin photoremovable protecting groups, which release... (Review)
Review
An overview of the history, mechanistic aspects and applications is provided for p-hydroxyphenacyl (pHP) and benzoin photoremovable protecting groups, which release biologically important leaving groups upon photolysis with UV light. Also discussed is (7-diethylaminocoumarin-4-yl)methyl (DEACM), a photoremovable protecting group that absorbs visible light. These are followed by the α-keto amides and naphtho- and benzothiophene-2-carboxanilides as caging groups, which eliminate leaving groups via photochemically produced zwitterionic intermediates. Also covered are amino-1,4-benzoquinones, which upon exposure to green and red wavelengths of light photorearrange to an unstable photoproduct that subsequently eliminates leaving groups in aqueous media. Selected examples are given that use these photoremovable protecting (caging) groups for the light-activated release of biologically important substrates under physiological conditions in cells and tissue as practical applications in biology, biochemistry and physiology. These caging groups have found significant applications because their photochemistry is efficient and a single coproduct is formed in addition to the photoreleased substrate.
Topics: Photochemistry; Photolysis; Ultraviolet Rays
PubMed: 34101860
DOI: 10.1111/php.13462 -
Water Science and Technology : a... 2011Perfluorooctanoic acid (PFOA) is very persistent in the environment and widely detected in the water environment. Only some advanced methods with extreme reaction...
Perfluorooctanoic acid (PFOA) is very persistent in the environment and widely detected in the water environment. Only some advanced methods with extreme reaction conditions are shown to be capable of degrading the compound efficiently, and almost all the earlier investigations used very high PFOA concentrations. The compound is detected normally at very low concentrations in the water environment, while mild reaction conditions for its degradation are preferable. This article aimed to elucidate photodegradation of PFOA in dilute aqueous solutions by combined UV wavelengths (185 nm+254 nm) and 254 nm using a newly designed UV jacket. PFOA degradation was greatly enhanced with the combined wavelengths with almost one hundred percent PFOA removals in four-hour reaction. The removals were well described by the first-order reaction kinetic. The removal efficiencies and rate values significantly decreased with smaller initial PFOA concentrations. But defluorination was greatly enhanced with smaller PFOA concentrations possibly due to accelerated decomposition of fluorinated intermediates of PFOA. Formic acid and acetic acid were two tentatively identified intermediates of PFOA photolysis while the former was a major intermediate predominantly controlling solution pH during the oxidation. The results demonstrated that PFOA photolysis by the combined wavelengths with mild reaction conditions can be greatly enhanced by proper design of UV jacket and reactor system.
Topics: Caprylates; Carboxylic Acids; Chromatography, Ion Exchange; Fluorides; Fluorocarbons; Half-Life; Halogenation; Hydrogen-Ion Concentration; Kinetics; Photolysis; Solutions; Ultraviolet Rays; Water
PubMed: 21252431
DOI: 10.2166/wst.2011.050 -
Water Research Jun 2021Fluoroquinolone (FQ) antibiotics are a group of contaminants of emerging environmental concern. In the present study, we demonstrated that norfloxacin (NORF) and...
Fluoroquinolone (FQ) antibiotics are a group of contaminants of emerging environmental concern. In the present study, we demonstrated that norfloxacin (NORF) and ofloxacin (OFLO), two typical FQs, have photochemical reactivity analogous to chromophoric dissolved natural organic matter (DOM) in surface waters and can sensitize the photodegradation of isoproturon (IPU), a phenylurea herbicide. Such photochemical reactivity is ascribed to the quinolone chromophore that is excited to a triplet state (FQ*) upon UV-A irradiation. FQ* further reacts with dissolved oxygen to give rise to singlet oxygen. FQ* steady-state concentrations of 6.72 × 10 and 1.27 × 10 M were measured in 10 μM NORF and OFLO solutions, respectively, under UV irradiation. The degradation of IPU was due to the reaction with FQ*, with bimolecular rate constants of 6.07 × 10 and 1.51 × 10 for NORF* and OFLO*, respectively. Intriguingly, NORF and OFLO per se were unstable and photolyzed during UV-A irradiation, but the photochemical reactivities of the solutions were not lost accordingly. High-resolution mass spectrometry analysis revealed that defluorination and piperazine moiety oxidation were the main photolysis pathways, while the core quinolone structure remained intact. Thus, the photolysis products largely inherited the photochemical reactivity of the parent compounds. Since all FQs share the same quinolone structure, similar photochemical reactivity is expected. The presence of FQs in surface water would affect the transformation and fate of coexisting compounds. To the best of our knowledge, this is the first study examining the environmental behavior of FQs as photosensitizers. The findings greatly advance the understandings of the influence of FQs in aquatic environment.
Topics: Anti-Bacterial Agents; Fluoroquinolones; Phenylurea Compounds; Photolysis; Water Pollutants, Chemical
PubMed: 33894578
DOI: 10.1016/j.watres.2021.117136