Non-Singlet Oxygen Kinetic Solvent Isotope Effects in Aquatic Photochemistry

Davis, Caroline A.; McNeill, Kristopher; Janssen, Elisabeth M.-L.

doi:10.1021/acs.est.8b01512

Cited by 39 publications

(42 citation statements)

References 44 publications

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“…It is expected that these binding sites should be more accessible to water molecules, which may explain the effect of H 2 O/D 2 O exchange. The observed enhancement of oxygen photoconsumption after exchanging H 2 O for D 2 O is consistent with the involvement of singlet oxygen, taking into account that in D 2 O singlet oxygen lifetime is about 15-fold longer than in H 2 O [40,41].…”

Section: Blue Light-induced Oxygen Consumptionsupporting

confidence: 83%

Photoreactivity of Bis-retinoid A2E Complexed with a Model Protein in Selected Model Systems

Furso

Szewczyk

Sarna

2020

Cell Biochem Biophys

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The bis-retinoid N-retinyl-N-retinylidene ethanolamine (A2E) is formed as a byproduct of visual cycle in retinal pigment epithelium (RPE). It contributes to golden-yellow fluorescence of the age pigment lipofuscin, which accumulates in RPE. Lipofuscin can generate a variety of reactive oxygen species (ROS) upon blue-light excitation. Although in model systems photoreactivity of A2E has been determined to be low, this bis-retinoid exhibited significant phototoxicity in RPE cells in vitro. Although the mechanism of A2E-mediated phototoxicity remains mostly unknown, we hypothesize that formation of A2E-adducts with different biomolecules may play an important role. In this study, we investigated the photochemical reactivity of A2E and its complex with bovine serum albumin (BSA) using UV–Vis absorption and emission spectroscopy, EPR-spin trapping, EPR-oximetry, time-resolved singlet oxygen phosphorescence, and the fluorogenic CBA probe. Our data show that A2E after complexation with this model protein photogenerated an increased level of ROS, particularly singlet oxygen. We also demonstrated the ability of A2E to oxidize BSA upon excitation with blue light in aqueous model systems. The data suggest that pyridinium bis-retinoid could oxidatively modify cellular proteins under physiological conditions.

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Section: Blue Light-induced Oxygen Consumptionsupporting

confidence: 83%

Photoreactivity of Bis-retinoid A2E Complexed with a Model Protein in Selected Model Systems

Furso

Szewczyk

Sarna

2020

Cell Biochem Biophys

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“…We oxidized EGT using 1 O 2 that was generated by using the photosensitizer rose bengal in the presence of a visible light source in 90% D 2 O for 20 min. The decision to use D 2 O instead of water or buffer was made because the lifetime of 1 O 2 is significantly longer in D 2 O due to the shifted vibrational frequencies of the D–O bonds, allowing for more extensive oxidation of our compounds [ 69 , 70 ]. We then analyzed the products of this reaction using MS, which is shown in Figure 8 .…”

Section: Resultsmentioning

confidence: 99%

Oxidized Forms of Ergothioneine Are Substrates for Mammalian Thioredoxin Reductase

et al. 2022

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Ergothioneine (EGT) is a sulfur-containing amino acid analog that is biosynthesized in fungi and bacteria, accumulated in plants, and ingested by humans where it is concentrated in tissues under oxidative stress. While the physiological function of EGT is not yet fully understood, EGT is a potent antioxidant in vitro. Here we report that oxidized forms of EGT, EGT-disulfide (ESSE) and 5-oxo-EGT, can be reduced by the selenoenzyme mammalian thioredoxin reductase (Sec-TrxR). ESSE and 5-oxo-EGT are formed upon reaction with biologically relevant reactive oxygen species. We found that glutathione reductase (GR) can reduce ESSE, but only with the aid of glutathione (GSH). The reduction of ESSE by TrxR was found to be selenium dependent, with non-selenium-containing TrxR enzymes having little or no ability to reduce ESSE. In comparing the reduction of ESSE by Sec-TrxR in the presence of thioredoxin to that of GR/GSH, we find that the glutathione system is 10-fold more efficient, but Sec-TrxR has the advantage of being able to reduce both ESSE and 5-oxo-EGT directly. This represents the first discovered direct enzymatic recycling system for oxidized forms of EGT. Based on our in vitro results, the thioredoxin system may be important for EGT redox biology and requires further in vivo investigation.

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“…15 Analogous experiments were performed for several diphenylamine radicals, produced by photosensitized one-electron oxidation of some fenamate-type drugs, using ascorbic acid as a quencher, 22 and for the quenching of the mefenamic acid radical by sesamol. 23 In a more recent study, the radical formed by one-electron oxidation of adenine by the sulfate radical and subsequent deprotonation was observed to react with catechol and three different purines regenerating adenine. 24 These radical kinetics data were used for an improved understanding of the abatement of mixtures of contaminants in advanced oxidation processes.…”

Section: ■ Introductionmentioning

confidence: 98%

Quenching of an Aniline Radical Cation by Dissolved Organic Matter and Phenols: A Laser Flash Photolysis Study

Leresche

Ludvíková

Heger

et al. 2020

Environ. Sci. Technol.

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Aromatic amines are relevant aquatic organic contaminants whose photochemical transformation is affected by dissolved organic matter (DOM). The goal of this study is to elucidate the underlying mechanism of the inhibitory effect of DOM on such reactions. The selected model aromatic amine, 4-(dimethylamino)benzonitrile (DMABN), was submitted to laser flash photolysis in the presence and absence of various model photosensitizers. The produced radical cation (DMABN •+ ) was observed to react with several phenols and different types of DOM on a time scale of ∼100 µs. The determined second-order rate constants for the quenching of DMABN •+ by phenols were in the range of (1.4 -26) × 10 8 M −1 s −1 and increased with increasing electron donor character of the aromatic ring substituent. For DOM, quenching rate constants increased with the phenolic content of the DOM. These results indicate the reduction of DMABN •+ to re-form its parent compound as the basic reaction governing the inhibitory effect. In addition, the photosensitized oxidation of the sulfonamide antibiotic sulfadiazine (SDZ) was studied. The observed radical intermediate of SDZ was quenched by 4-methoxyphenol less effectively than DMABN •+ , which was attributed to the lower reduction potential of this radical compared to DMABN •+ .

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Non-Singlet Oxygen Kinetic Solvent Isotope Effects in Aquatic Photochemistry

Cited by 39 publications

References 44 publications

Photoreactivity of Bis-retinoid A2E Complexed with a Model Protein in Selected Model Systems

Photoreactivity of Bis-retinoid A2E Complexed with a Model Protein in Selected Model Systems

Oxidized Forms of Ergothioneine Are Substrates for Mammalian Thioredoxin Reductase

Quenching of an Aniline Radical Cation by Dissolved Organic Matter and Phenols: A Laser Flash Photolysis Study

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