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Water Research Mar 2021Cyanotoxin-producing harmful algal blooms (HABs) are a global occurrence and pose ecotoxicological threats to humans and animals alike. The presence of cyanotoxins can... (Review)
Review
Cyanotoxin-producing harmful algal blooms (HABs) are a global occurrence and pose ecotoxicological threats to humans and animals alike. The presence of cyanotoxins can seriously harm or kill nearby wildlife and restrict a body of water's use as a drinking water supply and recreational site, making it imperative to fully understand their fate and transport in natural waters. Photodegradation contributes to the overall degradation of cyanotoxins in environmental systems, especially for those present in the photic zone of surface waters. This makes photochemical transformation mechanisms important factors to account for when assessing the persistence of cyanotoxins in environmental systems. This paper reviews current knowledge on the photodegradation rates and pathways of cyanotoxins that can occur over the course of HABs. Sensitized, or indirect, photolysis contributes to the degradation of all cyanotoxins addressed in this paper (anatoxins, cylindrospermopsins, domoic acids, microcystins, and nodularins), with hydroxyl radicals (•OH), excited triplet states formed from the absorption of light by dissolved organic matter (DOM*), and photosynthetic pigment sensitized pathways being of primary interest. Direct photolysis pathways play a less significant role, but are still relevant for most of the cyanotoxins discussed in this paper.
Topics: Animals; Harmful Algal Bloom; Humans; Hydroxyl Radical; Photolysis; Water Pollutants, Chemical
PubMed: 33494040
DOI: 10.1016/j.watres.2021.116804 -
Photochemistry and Photobiology Jul 2022The direct photolysis of estrone in solvents ranging from water to cyclohexane is reported. The photodegradation is dominated by lumiestrone, an epimer of estrone...
The direct photolysis of estrone in solvents ranging from water to cyclohexane is reported. The photodegradation is dominated by lumiestrone, an epimer of estrone resulting from the inversion of the methyl group at carbon 13, regardless of solvent and photolysis wavelength in the range 254-320 nm. Solvent addition products are also observed in lesser amounts. The photodegradation rate in water is an order of magnitude slower than in nonaqueous solvents. Short wavelength excitation enhances photodegradation. Together, these results suggest complicated photophysics underlie the photochemistry with implications for the remediation of environmental estrogens.
Topics: Estrone; Photochemistry; Photolysis; Solvents; Water
PubMed: 34664279
DOI: 10.1111/php.13542 -
The Science of the Total Environment Nov 2023The presence of antibiotics in surface waters is a potential driver of antibiotic resistance and thus of concern to human and environmental health. Key factors driving... (Review)
Review
The presence of antibiotics in surface waters is a potential driver of antibiotic resistance and thus of concern to human and environmental health. Key factors driving the potential impact of antibiotics are their persistence and transport in rivers and lakes. The goal of this study was to describe the peer-reviewed published literature on the photolysis (direct and indirect), sorption, and biodegradation of a selected group of antibiotic compounds following a scoping review methodology. Primary research from 2000 to 2021 was surveyed to compile information on these processes for 25 antibiotics from 6 classes. After compilation and assessment of the available parameters, the results indicate that information is present to predict the rates of direct photolysis and reaction with hydroxyl radical (an indirect photolysis process) for most of the selected antibiotics. There is insufficient or inconsistent information for including other indirect photolysis processes, biodegradation, or removal via sorption to settling particles for most of the targeted antibiotic compounds. Future research should focus on collecting fundamental parameters such as quantum yields, second-order rate constants, normalized biodegradation rates, and organic carbon or surface area normalized sorption coefficients rather than pseudo-first order rate constants or sorption equilibrium constants that apply only to specific conditions/sites.
Topics: Humans; Anti-Bacterial Agents; Photolysis; Water Pollutants, Chemical; Biodegradation, Environmental
PubMed: 37414169
DOI: 10.1016/j.scitotenv.2023.165301 -
The Journal of Organic Chemistry Oct 2022Hydropersulfides (RSSH) have received significant interest in the field of redox biology because of their intriguing biochemical properties. However, because RSSH are...
Hydropersulfides (RSSH) have received significant interest in the field of redox biology because of their intriguing biochemical properties. However, because RSSH are inherently unstable, their study is challenging, and as a result, the details of their physiological roles remain ill-defined. Herein, we report strategies to release RSSH utilizing photoremovable protecting groups. RSSH protection with the well-established -hydroxyphenacyl (HP) photoprotecting group resulted in inefficient RSSH photorelease along with complex chemistry. Therefore, an alternative precursor was examined in which a self-immolative linker was inserted between the HP group and RSSH, providing nearly quantitative RSSH release following photolysis at 365 nm. Inspired by these results, we also synthesized an analogous precursor derivatized with 7-diethylaminocoumarin (DEACM), a visible light-cleavable photoprotecting group. Photolysis of this precursor at 420 nm led to efficient RSSH release, and in vitro experiments demonstrated intracellular RSSH delivery in breast cancer MCF-7 cells.
Topics: Humans; Light; MCF-7 Cells; Oxidation-Reduction; Photolysis
PubMed: 36084133
DOI: 10.1021/acs.joc.2c01049 -
ACS Macro Letters Jan 2023We report on a fundamental feature of photoiniferter polymerizations mediated with trithiocarbonates and xanthates. The polymerizations were found to be highly dependent...
We report on a fundamental feature of photoiniferter polymerizations mediated with trithiocarbonates and xanthates. The polymerizations were found to be highly dependent on the activated electronic excitation of the iniferter. Enhanced rates of polymerization and greater control over molecular weights were observed for trithiocarbonate- and xanthate-mediated photoiniferter polymerizations when the n → π* transition of the iniferter was targeted compared to the polymerizations activating the π → π* transition. The disparities in rates of polymerization were attributed to the increased rate of C-S photolysis which was confirmed using model trapping studies. This study provides valuable insight into the role of electronic excitations in photoiniferter polymerization and provides guidance when selecting irradiation conditions for applications where light sensitivity is important.
Topics: Polymerization; Photolysis; Thiones; Sulfur Compounds
PubMed: 36533885
DOI: 10.1021/acsmacrolett.2c00683 -
Pest Management Science Sep 2020Chlorothalonil is a conventional chloroaromatic fungicide and is toxic to many aquatic species. This study was designed to investigate the effects of six flavonoids on...
BACKGROUND
Chlorothalonil is a conventional chloroaromatic fungicide and is toxic to many aquatic species. This study was designed to investigate the effects of six flavonoids on the photolysis of chlorothalonil under sunlight and artificial light.
RESULTS
Flavonoids sensitized the photolysis of chlorothalonil under sunlight and artificial light by 6.7-18.3 and 2.4-7.5 times, respectively, in comparison with a flavonoid-free control. Photosensitization effect of each of the six flavonoids was greater under sunlight irradiation than under high-pressure mercury lamp irradiation. Cyanidin showed greater photosensitization effects than luteolin, galangin, quercetin, morin and kaempferol. Chlorothalonil underwent photo-reductive dechlorination and no hydrolysis product was formed in the presence of flavonoids. Hydroxyl and hydrogen radicals were detected in the absence and presence of cyanidin, respectively, under light irradiation.
CONCLUSION
The photosensitization effect of flavonoids on chlorothalonil photolysis is apparently related to flavonoid structure and might be due to their hydrogen donation capacity. These results highlight benefit of using flavonoids to manage aquatic pollution and reduce aquatic toxicity, and have great relevance in predicting the degradation kinetics and biological impacts of chlorothalonil in surface water. © 2020 Society of Chemical Industry.
Topics: Flavonoids; Kinetics; Nitriles; Photolysis; Water; Water Pollutants, Chemical
PubMed: 32246548
DOI: 10.1002/ps.5842 -
Environmental Science and Pollution... Sep 2020The superoxide anion radical (O) is one of the most predominant reactive oxygen species (ROS), which is also involved in diverse chemical and biological processes. In...
The superoxide anion radical (O) is one of the most predominant reactive oxygen species (ROS), which is also involved in diverse chemical and biological processes. In this study, O was generated by irradiating riboflavin in an O-saturated solution using an ultraviolet lamp (λ = 365 nm) as the light source. The photochemical reduction of 1,4-benzoquinone (p-BQ) by O was explored by 355-nm laser flash photolysis (LFP) and 365-nm UV light steady irradiation. The results showed that the photodecomposition efficiency of p-BQ was influenced by the riboflavin concentration, p-BQ initial concentration, and pH values. The superoxide anion radical originating from riboflavin photolysis served as a reductant to react with p-BQ, forming reduced BQ radicals (BQ) with a second-order rate constant of 1.1 × 10 L mol s. The main product of the photochemical reaction between p-BQ and O was hydroquinone (HQ). The present work suggests that the reaction with O is a potential transformation pathway of 1, 4-benzoquinone in atmospheric aqueous environments.
Topics: Benzoquinones; Oxidation-Reduction; Photolysis; Reactive Oxygen Species; Riboflavin; Superoxides
PubMed: 32488712
DOI: 10.1007/s11356-020-09422-8 -
Journal of Hazardous Materials Oct 2023Three novel neonicotinoids (cycloxaprid, flupyradifurone and sulfoxaflor) were designed to reduce the biotoxicity for non-target organisms. These neonicotinoids were...
Three novel neonicotinoids (cycloxaprid, flupyradifurone and sulfoxaflor) were designed to reduce the biotoxicity for non-target organisms. These neonicotinoids were photolyzed under light radiation, but it was unclear for the photo-enhanced toxicity and influences of the novel modifying group of the three neonicotinoids. The photolysis and photo-enhanced toxicity experiments were performed for the three neonicotinoids, coupled with quantum chemistry calculation, the mechanisms of photolysis, photo-enhanced toxicity and the influences of novel modifying groups were analyzed. The results showed the photolysis pathways were enriched as compared with previous neonicotinoids due to the composition of modifying groups, singlet oxygen and hydroxyl participated the photolysis of cycloxaprid and flupyradifurone. All tested neonicotinoids exhibited photo-enhanced toxicity to Vibrio fischeri. Due to the difference of photolysis mechanism and toxicity to V. fischeri, the photo-enhanced toxicity curves showed diverse variation when histidine, tert-butanol or dissolved organic matters was in presence of the test solutions. The impact of novel modifying groups over photolysis and photo-enhanced toxicity were analyzed based on the comparison with previous neonicotinoids, theoretically predicted UV-Vis spectra and photo-physical/chemical property descriptors. The data showed the composition of novel modifying group increased the light absorption and photo-chemical activities for the three neonicotinoids.
Topics: Photolysis; Neonicotinoids; 4-Butyrolactone; Water Pollutants, Chemical; Aliivibrio fischeri
PubMed: 37494794
DOI: 10.1016/j.jhazmat.2023.132132 -
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 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