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The Journal of Physical Chemistry... Dec 2021UV photodissociation of α-alanine was studied by parahydrogen matrix isolation infrared spectroscopy. The temporal behavior of Fourier transform infrared spectra...
UV photodissociation of α-alanine was studied by parahydrogen matrix isolation infrared spectroscopy. The temporal behavior of Fourier transform infrared spectra revealed that UV irradiation at 213 nm yielded the HOCO radical as a direct photoproduct from the S excited state. The concentration of HOCO quickly approached a steady state due to secondary photodissociation of HOCO to produce CO + H or CO + OH. On the other hand, no photoproducts were detected by S excitation at 266 nm. Irradiation of fully deuterated α-alanine at 213 nm yielded ∼2 times more -DOCO radicals than the lower energy isomer -DOCO, indicating that the conformation of the hydroxyl group is fairly well-preserved upon photodissociation of α-alanine. The present study suggests that HOCO may be a good tracer species in the search for amino acids in interstellar space.
Topics: Alanine; Carbon Dioxide; Isomerism; Photolysis; Quantum Theory; Ultraviolet Rays
PubMed: 34889613
DOI: 10.1021/acs.jpclett.1c03104 -
Environmental Science & Technology Jun 2023Nitrate photolysis is a vital process in secondary NOx release into the atmosphere. The heterogeneous oxidation of SO due to nitrate photolysis has been widely reported,...
Nitrate photolysis is a vital process in secondary NOx release into the atmosphere. The heterogeneous oxidation of SO due to nitrate photolysis has been widely reported, while the influence of SO on nitrate photolysis has rarely been investigated. In this study, the photolysis of nitrate on different substrates was investigated in the absence and presence of SO. In the photolysis of NHNO on the membrane without mineral oxides, NO, NO, HONO, and NH decreased by 17.1, 6.0, 12.6, and 57.1% due to the presence of SO, respectively. In the photolysis of NHNO on the surface of mineral oxides, SO also exhibited an inhibitory effect on the production of NOx, HONO, and NH due to its reducibility and acidic products, while the increase in surface acidity due to the accumulation of abundant sulfate on TiO and MgO promoted the release of HONO. On the photoactive oxide TiO, HSO, generated by the uptake of SO, could compete for holes with nitrate to block nitrate photolysis. This study highlights the interaction between the heterogeneous oxidation of SO and nitrate photolysis and provides a new perspective on how SO affects the photolysis of nitrate absorbed on the photoactive oxides.
Topics: Nitrates; Photolysis; Oxides; Minerals
PubMed: 37235870
DOI: 10.1021/acs.est.3c01082 -
The Journal of Biological Chemistry Sep 1962
Topics: Chymotrypsin; Light; Photolysis
PubMed: 13913310
DOI: No ID Found -
Photochemistry and Photobiology Nov 1972
Topics: Bromouracil; Hydrogen-Ion Concentration; Photolysis; Polynucleotides; Ultraviolet Rays
PubMed: 4670722
DOI: 10.1111/j.1751-1097.1972.tb06307.x -
The Journal of Organic Chemistry Jan 2022Two fluorophores bound with a short photoreactive bridge are fascinating structures and remained unexplored. To investigate the synthesis and photolysis of such dyes, we...
Two fluorophores bound with a short photoreactive bridge are fascinating structures and remained unexplored. To investigate the synthesis and photolysis of such dyes, we linked two rhodamine dyes via a diazoketone bridge (-COCN-) attached to position 5' or 6' of the pendant phenyl rings. For that, the mixture of 5'- or 6'-bromo derivatives of the parent dye was prepared, transformed into 1,2-diarylacetylenes, hydrated to 1,2-diarylethanones, and converted to diazoketones ArCOCNAr. The high performance liquid chromatography (HPLC) separation gave four individual regioisomers of ArCOCNAr. Photolysis of the model compound─CHCOCNCH─in aqueous acetonitrile at pH 7.3 and under irradiation with 365 nm light provided diphenylacetic acid amide (Wolff rearrangement). However, under the same conditions, ArCOCNAr gave mainly α-diketones ArCOCOAr. The migration ability of the very bulky dye residues was low, and the Wolff rearrangement did not occur. We observed only moderate fluorescence increase, which may be explained by the insufficient quenching ability of diazoketone bridge (-COCN-) and its transformation into another (weaker) quencher, 1,2-diarylethane-1,2-dione.
Topics: Fluorescent Dyes; Photolysis; Rhodamines; Spectrometry, Fluorescence; Water
PubMed: 34919387
DOI: 10.1021/acs.joc.1c01721 -
Journal of Environmental Sciences... Dec 2023Vacuum ultraviolet (VUV) photolysis is a facile method for volatile organic compounds (VOCs) elimination, but is greatly limited by the relatively low removal efficiency...
Vacuum ultraviolet (VUV) photolysis is a facile method for volatile organic compounds (VOCs) elimination, but is greatly limited by the relatively low removal efficiency and the possible secondary pollution. To overcome above drawbacks, we developed an efficient method for VOCs elimination via VUV photolysis coupled with wet scrubbing process. In this coupled process, volatile toluene, a representative of VOCs, was oxidized by the gas-phase VUV photolysis, and then scrubbed into water for further oxidation by the liquid-phase VUV photolysis. More than 96% of toluene was efficiently removed by this coupled process, which was 2 times higher than that in the gas-phase VUV photolysis. This improvement was attributed to the synergistic effect between gas-phase and liquid-phase VUV photolysis. O and HO are the predomination reactive species for the toluene degradation in this coupled process, and the generation of O in gas-phase VUV photolysis can efficiently enhance the HO production in liquid-phase VUV photolysis. The result from in-situ proton transfer reaction ionization with mass analyzer (PTR-MS) further suggested that most intermediates were trapped by the wet scrubbing process and efficiently oxidized by the liquid-phase VUV photolysis, showing a high performance for controlling the secondary pollution. Furthermore, the result of stability test and the reuse of solution demonstrated that this coupled process has a highly stable and sustainable performance for toluene degradation. This study presents an environmentally benign and highly efficient VUV photolysis for gaseous VOCs removal in the wet scrubbing process.
Topics: Photolysis; Vacuum; Volatile Organic Compounds; Oxidation-Reduction; Gases; Toluene
PubMed: 37673533
DOI: 10.1016/j.jes.2022.05.002 -
Environmental Science & Technology May 2021The United States Environmental Protection Agency's Chemical Transformation Simulator (CTS) platform implemented the first freely available reaction library to predict...
The United States Environmental Protection Agency's Chemical Transformation Simulator (CTS) platform implemented the first freely available reaction library to predict direct photolysis products of organic contaminants in aquatic systems. However, the initial version of the reaction library did not differentiate the formation likelihood of each predicted product, and therefore, the number of predicted products that are not observed tended to exponentially increase with the prediction generation. To alleviate this problem, we first employed relative reasoning algorithms to remove unlikely products. We then ranked different reaction schemes according to their transformation kinetics and removed slowly forming products. Applying the two strategies improved the precision (the percentage of correctly predicted products over all predicted products) by 34% and 53% for the internal evaluation set and the external evaluation set, respectively, when products from three generations were considered. This improved library also revealed new research directions to improve predictions of the dominant phototransformation products.
Topics: Kinetics; Photolysis; Water Pollutants, Chemical
PubMed: 33881833
DOI: 10.1021/acs.est.0c08745 -
Environmental Science & Technology Dec 2017New insensitive munitions explosives, including 2,4-dinitroanisole (DNAN), are replacing traditional explosive compounds to protect soldiers and simplify transport...
New insensitive munitions explosives, including 2,4-dinitroanisole (DNAN), are replacing traditional explosive compounds to protect soldiers and simplify transport logistics. Despite the occupational safety benefits of these new explosives, feasible strategies for cleaning up DNAN from soil and water have not been developed. Here, we evaluate the metabolism of DNAN by the model plant Arabidopsis to determine whether phytoremediation can be used to clean up contaminated sites. Furthermore, we evaluate the role of photodegradation of DNAN and its plant metabolites within Arabidopsis leaves to determine the potential impact of photolysis on the phytoremediation of contaminants. When exposed to DNAN for three days, Arabidopsis took up and metabolized 67% of the DNAN in hydroponic solution. We used high resolution and tandem mass spectrometry in combination with stable-isotope labeled DNAN to confirm ten phase II DNAN metabolites in Arabidopsis. The plants separately reduced both the para- and ortho-nitro groups and produced glycosylated products that accumulated within plant tissues. Both DNAN and a glycosylated metabolite were subsequently photolyzed within leaf tissue under simulated sunlight, and [N]DNAN yielded NO in leaves. Therefore, photolysis inside leaves may be an important, yet under-explored, phytoremediation mechanism.
Topics: Anisoles; Arabidopsis; Explosive Agents; Photolysis
PubMed: 29131608
DOI: 10.1021/acs.est.7b04220 -
Environmental Science & Technology Sep 2018Determining the influence of higher order structure on UVC photolysis will help inform predictions of nucleic acid fate and microorganism inactivation. We measured the...
Determining the influence of higher order structure on UVC photolysis will help inform predictions of nucleic acid fate and microorganism inactivation. We measured the direct UV photolysis kinetics of four model viral genomes composed of single-stranded and double-stranded RNA (ssRNA and dsRNA, respectively), as well as single-stranded and double-stranded DNA (ssDNA and dsDNA, respectively), in ultrapure water, in phosphate buffered saline (PBS), and encapsidated in their native virus particles. The photolysis rate constants of naked nucleic acids measured by qPCR (RT-qPCR for RNA) and normalized by the number of bases measured in a particular sequence exhibited the following trend: ssDNA > ssRNA ≈ dsDNA > dsRNA. In PBS, naked ssRNA bases reacted, on average, 24× faster than the dsRNA bases, whereas naked ssDNA bases reacted 4.3× faster than dsDNA bases. Endogenous indirect photolysis involving O and ·OH was ruled out as a major contributing factor in the reactions. A comparison of our measured rate constants with rate constants reported in the literature shows a general agreement among the nucleic acid UV direct photolysis kinetics. Our results underscore the high resistance of dsRNA to UVC photolysis and demonstrate the role that nucleic acid structure and solution chemistry play in photoreactivity.
Topics: DNA; DNA, Single-Stranded; Genome, Viral; Photolysis; RNA
PubMed: 30106282
DOI: 10.1021/acs.est.8b02308 -
The Journal of Organic Chemistry Dec 1975
Topics: Cholestadienes; Photolysis
PubMed: 1195045
DOI: 10.1021/jo00913a040