-
Water Research Jun 2012Ultraviolet (UV) filters are vital constituents of sunscreens and other personal care products since they absorb, reflect and/or scatter UV radiation, therefore... (Review)
Review
Ultraviolet (UV) filters are vital constituents of sunscreens and other personal care products since they absorb, reflect and/or scatter UV radiation, therefore protecting us from the sun's deleterious UV radiation and its effects. However, they suffer degradation, mainly through exposure towards sunlight and from reactions with disinfectant products such as chlorine. On the basis of their increasing production and use, UV filters and their degradation products have already been detected in the aquatic environment, especially in bathing waters. This paper presents a comprehensive review on the work done so far as to identify and determine the by-products of UV filter photodegradation in aqueous solutions and those subsequent to disinfection-induced degradation in chlorinated aqueous solutions, namely swimming pools.
Topics: Chlorine; Filtration; Halogenation; Photolysis; Solutions; Ultraviolet Rays
PubMed: 22513303
DOI: 10.1016/j.watres.2012.03.057 -
Huan Jing Ke Xue= Huanjing Kexue Sep 2003Propisochlor in water was irradiated at room temperature by a 400 W high pressure mercury lamp and sunlight, respectively. Influence of light and initiative...
Propisochlor in water was irradiated at room temperature by a 400 W high pressure mercury lamp and sunlight, respectively. Influence of light and initiative concentration of propisochlor on the photolysis were studied. The results showed that under the irradiation of sunlight the photolysis fitted first order kinetics with only 5.5% degradation after one hour's irradiation in the quartz tube, that was a slow rate; while under the irradiation of high pressure mercury lamp the photolysis can be described by a double-chamber model, in which the degradation rate can reach 80.9% after 1 h. The higher the initiative concentration of propisochlor was, the slower the photolysis rate became, and the photolysis of propisochlor was influenced by the increasing photo-products. The six main photodegradation products were identified using GC-MS method. The aromatic ring was proved to be intact during the process. And the photolysis mechanism was then assumed on the basis of the photo-products detected.
Topics: Acetamides; Herbicides; Kinetics; Photolysis
PubMed: 14719274
DOI: No ID Found -
Analytical and Bioanalytical Chemistry Jan 2006In order to reduce the color quenching in the measurement of tritium in urine by liquid scintillation counting , UV irradiation was applied to decompose the organic...
In order to reduce the color quenching in the measurement of tritium in urine by liquid scintillation counting , UV irradiation was applied to decompose the organic substances in the sample. Urine was decolorized under UV irradiation in the presence of hydrogen peroxide. As a result, color quenching was considerably suppressed and higher counting efficiency of tritium was obtained. This UV treatment made it possible to increase the urine content in the sample from 2 to 40% (v/v) without significant decrease of counting efficiency. Either higher sensitivity or shorter analysis time was achieved in the tritium measurement by the augmentation of urine content. When the measurement time was 30 min, the detection limit of tritium defined as 3s was 0.03 Bq/ml. At the expense of some sensitivity (set at a detection limit of 0.3 Bq/ml), the measurement time was shortened to 0.5 min. These results will make a great improvement to routine tritium monitoring as well as to emergency monitoring in mass tritium exposure.
Topics: Color; Photolysis; Scintillation Counting; Tritium; Ultraviolet Rays; Urine; Water
PubMed: 16341510
DOI: 10.1007/s00216-005-0166-7 -
Journal of the Chemical Society. Perkin... 1974
Topics: Benzene; Furans; Photochemistry; Photolysis; Uracil
PubMed: 4477772
DOI: No ID Found -
Pest Management Science Feb 2002The photodegradation of fluchloralin by UV irradiation or sunlight in aqueous methanolic solution has been examined. In the presence of titanium dioxide five...
The photodegradation of fluchloralin by UV irradiation or sunlight in aqueous methanolic solution has been examined. In the presence of titanium dioxide five photoproducts were obtained, but only four in its absence. One photoproduct, 2, 2'-azoxy-bis(alpha,alpha,alpha-trifluoro-6-nitro-p-toluidine) is reported for the first time as a metabolite of fluchloralin. In natural sunlight the rate of degradation was higher than in UV light and titanium dioxide had almost no effect on the rate of degradation.
Topics: Aniline Compounds; Biodegradation, Environmental; Cyclic N-Oxides; Gas Chromatography-Mass Spectrometry; Kinetics; Magnetic Resonance Spectroscopy; Methanol; Photolysis; Spectrophotometry, Infrared; Sunlight; Titanium; Toluidines; Ultraviolet Rays; Water
PubMed: 11852643
DOI: 10.1002/ps.425 -
Angewandte Chemie (International Ed. in... Oct 2023Cellular membranes, including the plasma and endosome membranes, are barriers to outside proteins. Various vehicles have been devised to deliver proteins across the...
Cellular membranes, including the plasma and endosome membranes, are barriers to outside proteins. Various vehicles have been devised to deliver proteins across the plasma membrane, but in many cases, the payload gets trapped in the endosome. Here we designed a photo-responsive phase-separating fluorescent molecule (PPFM) with a molecular weight of 666.8 daltons. The PPFM compound condensates as fluorescent droplets in the aqueous solution by liquid-liquid phase separation (LLPS), which disintegrate upon photoirradiation with a 405 nm light-emitting diode (LED) lamp within 20 min or a 405 nm laser within 3 min. The PPFM coacervates recruit a wide range of peptides and proteins and deliver them into mammalian cells. Photolysis disperses the payload from condensates into the cytosolic space. Altogether, a type of small molecules that are photo-responsive and phase separating are discovered; their coacervates can serve as transmembrane vehicles for intracellular delivery of proteins, whereas photo illumination triggers the cytosolic distribution of the payload.
Topics: Cell Membrane; Peptides; Photolysis; Light
PubMed: 37648812
DOI: 10.1002/anie.202307045 -
Physical Chemistry Chemical Physics :... Sep 2016Photophysical investigations of the canonical nucleobases that make up DNA and RNA during the past 15 years have revealed that excited states formed by the absorption of... (Review)
Review
Photophysical investigations of the canonical nucleobases that make up DNA and RNA during the past 15 years have revealed that excited states formed by the absorption of UV radiation decay with subpicosecond lifetimes (i.e., <10(-12) s). Ultrashort lifetimes are a general property of absorbing sunscreen molecules, suggesting that the nucleobases are molecular survivors of a harsh UV environment. Encoding the genome using photostable building blocks is an elegant solution to the threat of photochemical damage. Ultrafast excited-state deactivation strongly supports the hypothesis that UV radiation played a major role in shaping molecular inventories on the early Earth before the emergence of life and the subsequent development of a protective ozone shield. Here, we review the general physical and chemical principles that underlie the photostability, or "UV hardiness", of modern nucleic acids and discuss the possible implications of these findings for prebiotic chemical evolution. In RNA and DNA strands, much longer-lived excited states are observed, which at first glance appear to increase the risk of photochemistry. It is proposed that the dramatically different photoproperties that emerge from assemblies of photostable building blocks may explain the transition from a world of molecular survival to a world in which energy-rich excited electronic states were eventually tamed for biological purposes such as energy transduction, signaling, and repair of the genetic machinery.
Topics: DNA; Electron Transport; Nucleotides; Photolysis; RNA; Ultraviolet Rays
PubMed: 27539809
DOI: 10.1039/c6cp04230a -
Photochemistry and Photobiology Mar 2022The photolysis reactions of (8-cyano-7-hydroxyquinolin-2-yl)methyl (CyHQ)-caged amines have been investigated using time-resolved spectroscopy methods. Unexpectedly, an...
The photolysis reactions of (8-cyano-7-hydroxyquinolin-2-yl)methyl (CyHQ)-caged amines have been investigated using time-resolved spectroscopy methods. Unexpectedly, an unconventional Hofmann-Martius rearrangement reaction with high yield and regioselectivity occurred during the photolysis of some CyHQ-protected dialkylanilines (such as compounds 1a and 2a). To have more insights into the mechanism of this unexpected photorearrangement reaction, we characterized the reaction intermediates directly using time-resolved spectroscopy. Our new results showed that the anionic form of compound 1a was photoexcited to the singlet excited state, then a heterolytic cleavage of the C-N bond took place to give CyHQ and the corresponding aniline. Thereafter, the recombined intermediate 6 was found to appear in about 19.7 and 44.3 ps for 1a (A) and 2a (A), respectively, before the generation of an ortho-substituted aniline (1b and 2b) via the excited-state deprotonation of 6. Thus, a logical photodynamic mechanism of this photoinduced Hofmann-Martius rearrangement reaction was deduced. This new insight into the reaction mechanisms may be helpful for the design of novel related photoactivatable aniline molecules and for understanding other similar photorearrangement reaction mechanisms.
Topics: Amines; Aniline Compounds; Photolysis; Quinolines; Spectrum Analysis
PubMed: 34812490
DOI: 10.1111/php.13566 -
The Journal of Chemical Physics Aug 2010Photodissociation of amino acid tryptophan in a molecular beam at wavelengths of 212.8 and 193 nm, corresponding to excitation to the second and third absorption bands,...
Photodissociation of amino acid tryptophan in a molecular beam at wavelengths of 212.8 and 193 nm, corresponding to excitation to the second and third absorption bands, was investigated using multimass ion imaging techniques. The respective wavelengths also represent excitation to the edge of a positive circular dichroism band and the center of a negative circular dichroism band of L-tryptophan. Only one dissociation channel was observed at both photolysis wavelengths: C(8)NH(6)CH(2)CHNH(2)COOH-->C(8)NH(6)CH(2)+CHNH(2)COOH. Dissociation rates were found to be 1.3x10(6) and 5x10(6) s(-1) at the respective wavelengths. Comparison to theoretical calculation indicates that dissociation occurs on the ground state after internal conversion. Implication of asymmetric photolysis is discussed.
Topics: Electrons; Kinetics; Photolysis; Thermodynamics; Tryptophan
PubMed: 20726642
DOI: 10.1063/1.3474992 -
Chembiochem : a European Journal of... Nov 2015It has been postulated that sugar radicals and related species are involved in oxidative events involving RNA. To determine the contribution, if any, of these species to...
It has been postulated that sugar radicals and related species are involved in oxidative events involving RNA. To determine the contribution, if any, of these species to the deleterious effects of the endogenous exposome, it is important to unambiguously identify their degradation products. C5'-Pivaloyl uridine was successfully synthesized and subsequently photolytically converted to a C5'-uridinyl radical. Generation of the radical under anaerobic conditions in the presence of glutathione led to the formation of the expected reduction product, uridine. However, regardless of the presence or absence of reductant, the base elimination product, uracil, was also observed. Mass balances and product distributions were dependent upon the pH of the photolysis mixture. At low pH, trapping with glutathione successfully competed with base loss. These results indicate that this precursor should function efficiently in an investigation of the fate of the C5'-uridinyl radical in RNA oligomers.
Topics: Crystallography, X-Ray; Free Radicals; Glutathione; Hydrogen-Ion Concentration; Light; Molecular Conformation; Photolysis; RNA; Uridine
PubMed: 26338230
DOI: 10.1002/cbic.201500330