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Scientific American May 1960
Topics: Chemistry Techniques, Analytical; Light; Photolysis
PubMed: 13829717
DOI: No ID Found -
Nature Dec 1975
Topics: Lasers; Photochemistry; Photolysis; Retinal Pigments; Rhodopsin; Spectrum Analysis; Tryptophan
PubMed: 1207766
DOI: 10.1038/258768a0 -
Photochemistry and Photobiology Sep 1974
Topics: Flavins; Lasers; Photolysis; Spectrometry, Fluorescence; Time Factors
PubMed: 4414059
DOI: 10.1111/j.1751-1097.1974.tb06571.x -
Nature May 1956
Topics: Humans; Photolysis; Retina; Rhodopsin
PubMed: 13322011
DOI: 10.1038/177989b0 -
Chemistry & Biodiversity Jun 2010Amino acids that pass the RNA machinery in living organisms occur in L-configuration. The question on the evolutionary origin of this biomolecular asymmetry remains...
Amino acids that pass the RNA machinery in living organisms occur in L-configuration. The question on the evolutionary origin of this biomolecular asymmetry remains unanswered to this day. Amino acids were detected in artificially produced interstellar ices, and L-enantiomer-enriched amino acids were identified in CM-type meteorites. This hints at a possible interstellar/circumstellar origin of the amino acids themselves as well as their stereochemical asymmetry. Based upon the current knowledge about the occurrence of circularly-polarized electromagnetic radiation in interstellar environments, we subjected rac-leucine to far-UV circularly-polarized synchrotron radiation. Asymmetric photolysis was followed by an analysis in an enantioselective GC/MS system. Here, we report on an advanced photolysis rate of more than 99% for leucine. The results indicate that high photolysis rates can occur under the chosen conditions, favoring enantioselective photolysis. In 2014, the obtained results will be reexamined by cometary mission Rosetta.
Topics: Circular Dichroism; Leucine; Photolysis; Stereoisomerism; Synchrotrons
PubMed: 20564679
DOI: 10.1002/cbdv.200900311 -
Environmental Science & Technology Apr 2020Heterogeneous oxidation of SO is an effective production pathway of sulfate in the atmosphere. We recently reported a novel pathway for the heterogeneous oxidation of SO...
Heterogeneous oxidation of SO is an effective production pathway of sulfate in the atmosphere. We recently reported a novel pathway for the heterogeneous oxidation of SO by in-particle oxidants (OH, NO, and NO/HNO) produced from particulate nitrate photolysis ( , , 8757-8766). Particulate nitrate is often found to coexist with chloride and other halide ions, especially in aged sea-salt aerosols and combustion aerosols. Reactive uptake experiments of SO with UV-irradiated nitrate particles showed that sulfate production rates were enhanced by a factor of 1.4, 1.3, and 2.0 in the presence of Cl, Br, and I, respectively, compared to those in the absence of halide ions. The larger sulfate production was attributed to enhanced nitrate photolysis promoted by the increased incomplete solvation of nitrate at the air-particle interface due to the presence of surface-active halide ions. Modeling results based on the experimental data showed that the nitrate photolysis rate constants increased by a factor of 2.0, 1.7, and 3.7 in the presence of Cl, Br, and I, respectively. A linear relation was found between the nitrate photolysis rate constant, , and the initial molar ratio of Cl to NO, [Cl]/[NO], as = 9.7 × 10[Cl]/[NO] + 1.9 × 10 at [Cl]/[NO] below 0.2. The present study demonstrates that the presence of halide ions enhances sulfate production produced during particulate nitrate photolysis and provides insights into the enhanced formation of in-particle oxidants that may increase atmospheric oxidative capacity.
Topics: Atmosphere; Nitrates; Nitrogen Oxides; Photolysis; Sulfates
PubMed: 32126769
DOI: 10.1021/acs.est.9b06445 -
Unveiling the Mechanism of Photodamage to Sphingolipid Molecules via Laser Flash Photolysis and EPR.Photochemistry and Photobiology 2023Sphingolipids are involved in the maintenance of the skin barrier function and regulate cellular processes of keratinocytes. The work reported here is designed to...
Sphingolipids are involved in the maintenance of the skin barrier function and regulate cellular processes of keratinocytes. The work reported here is designed to uncover details of the mechanism of damage to such lipids by UV radiation. Our approach employs laser flash photolysis and electron paramagnetic resonance (EPR) spectrometry to explore the mechanism of the decay reactions, and to determine the associated kinetic parameters. To interpret our experiments, we computed both excitation energies and EPR parameters of radicals formed during photolysis. Employing the spin-trap EPR method confirmed the formation of both carbon- and nitrogen-centered radicals. Thus, we can conclude that the photodecomposition of sphingolipids and their analogues proceeds by Norrish type I reactions with the formation of both nitrogen-centered and alkyl radicals.
Topics: Electron Spin Resonance Spectroscopy; Photolysis; Lasers; Nitrogen; Free Radicals
PubMed: 36943199
DOI: 10.1111/php.13804 -
Advanced Healthcare Materials Nov 2020Photoresponsive drug release systems can enhance drug accumulation at the sites where light is applied. Nowadays, the photocleavable groups used in the systems usually...
Photoresponsive drug release systems can enhance drug accumulation at the sites where light is applied. Nowadays, the photocleavable groups used in the systems usually require ultraviolet or blue light irradiation, which limits tissue penetration depth and is harmful to normal cells and living bodies. A one-photon upconversion-like photolysis strategy, which can cleave green light-activatable prodrugs with red light at the presence of a red light-excitable photosensitizer in organic solvents, is developed. However, both the prodrug and photosensitizer are hydrophobic and their energy transfer process is sensitive to oxygen molecules. Here, a simple strategy to address these problems by loading the two components in biocompatible and biodegradable polymeric micelles, is presented. The developed low-irradiance red light-triggered drug release system has a size around 40 nm and exhibits good stability in aqueous solutions. The micellar encapsulation protects the photolysis reaction from oxygen quenching in normoxia aqueous solutions. The therapeutic effect of the system enhanced by the redlight irradiation is demonstrated through in vitro and in vivo studies, indicating promising potential in cancer therapy. The study provides the first example and also an important reference for applying one-photon upconversion-like photolysis in biomedical applications.
Topics: Drug Liberation; Micelles; Nanoparticles; Photolysis; Polymers; Prodrugs
PubMed: 32985134
DOI: 10.1002/adhm.202001118 -
Environmental Science & Technology May 2021Particulate nitrate photolysis can produce oxidants (i.e., OH, NO, and NO/HNO) in aqueous droplets and may play a potential role in increased atmospheric oxidative...
Particulate nitrate photolysis can produce oxidants (i.e., OH, NO, and NO/HNO) in aqueous droplets and may play a potential role in increased atmospheric oxidative capacity. Our earlier works have reported on the SO oxidation promoted by nitrate photolysis to produce sulfate. Here, we used glyoxal as a model precursor to examine the role of particulate nitrate photolysis in the formation of secondary organic aerosol (SOA) from particle-phase oxidation of glyoxal by OH radicals. Particles containing sodium nitrate and glyoxal were irradiated at 300 nm. Interestingly, typical oxidation products of oxalic acid, glyoxylic acid, and higher-molecular-weight products reported in the literature were not found in the photooxidation process of glyoxal during nitrate photolysis in the particle phase. Instead, formic acid/formate production was found as the main oxidation product. At glyoxal concentration higher than 3 M, we found that the formic acid/formate production rate increases significantly with increasing glyoxal concentration. Such results suggest that oxidation of glyoxal at high concentrations by OH radicals produced from nitrate photolysis in aqueous particles may not contribute significantly to SOA formation since formic acid is a volatile species. Furthermore, recent predictions of formic acid/formate concentration from the most advanced chemical models are lower than ambient observations at both the ground level and high altitude. The present study reveals a new insight into the production of formic acid/formate as well as a sink of glyoxal in the atmosphere, which may partially narrow the gap between model predictions and field measurements in both species.
Topics: Aerosols; Formates; Glyoxal; Nitrates; Photolysis
PubMed: 33861585
DOI: 10.1021/acs.est.0c08199 -
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