Degradation of Tryptophan by UV Irradiation: Influencing Parameters and Mechanisms

The chlorination of dissolved amino acids can generate disinfection by-products (DBPs). To prevent the formation of DBPs, we examined the UV-induced degradation of tryptophan (Trp). In order to further understand the impact of UV disinfection on Trp, the effects of initial concentrations of Trp, pH, temperature, concentrations of NO3−, HCO3− and Cl− on Trp removal were investigated, and a degradation mechanism was also proposed. The results demonstrated that degradation fitted a pseudo first-order reaction kinetic model. The degradation of Trp was mainly caused by direct UV degradation. The apparent rate constant kobs decreased with the increase in initial Trp concentration and increased with increases in pH and temperature. The thermal degradation activation energy was 19.65 kJ/mol. Anions in water also had a significant influence on the degradation of Trp. HCO3− and NO3− contributed to the kobs of Trp, but Cl− inhibited the degradation rate. By electron paramagnetic resonance (EPR) spectroscopy, ·OH was proven to be formed during the degradation of Trp by UV. Based on the intermediate products of C11H15NO3, C10H15N and C9H13N detected by LC-MS-MS, the degradation pathway of Trp was speculated.

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The impact of particulate electron paramagnetic resonance oxygen sensors on fluorodeoxyglucose imaging characteristics detected via positron emission tomography

Scientific Reports ◽

10.1038/s41598-021-82754-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Philip E. Schaner ◽

Ly-Binh-An Tran ◽

Bassem I. Zaki ◽

Harold M. Swartz ◽

Eugene Demidenko ◽

...

Keyword(s):

Fdg Pet ◽

Oxygen Sensor ◽

Oxygen Sensors ◽

Paramagnetic Resonance ◽

Imaging Characteristics ◽

Positron Emission ◽

Pet Ct ◽

Fdg Pet Ct ◽

The Impact ◽

Electron Paramagnetic

AbstractDuring a first-in-humans clinical trial investigating electron paramagnetic resonance tumor oximetry, a patient injected with the particulate oxygen sensor Printex ink was found to have unexpected fluorodeoxyglucose (FDG) uptake in a dermal nodule via positron emission tomography (PET). This nodule co-localized with the Printex ink injection; biopsy of the area, due to concern for malignancy, revealed findings consistent with ink and an associated inflammatory reaction. Investigations were subsequently performed to assess the impact of oxygen sensors on FDG-PET/CT imaging. A retrospective analysis of three clinical tumor oximetry trials involving two oxygen sensors (charcoal particulates and LiNc-BuO microcrystals) in 22 patients was performed to evaluate FDG imaging characteristics. The impact of clinically used oxygen sensors (carbon black, charcoal particulates, LiNc-BuO microcrystals) on FDG-PET/CT imaging after implantation in rat muscle (n = 12) was investigated. The retrospective review revealed no other patients with FDG avidity associated with particulate sensors. The preclinical investigation found no injected oxygen sensor whose mean standard uptake values differed significantly from sham injections. The risk of a false-positive FDG-PET/CT scan due to oxygen sensors appears low. However, in the right clinical context the potential exists that an associated inflammatory reaction may confound interpretation.

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Catalytic and Electron Paramagnetic Resonance Spectroscopic Characterization of γ-Al2O3 in a Non-Thermal Plasma

Journal of Advanced Oxidation Technologies ◽

10.1515/jaots-2005-0116 ◽

2005 ◽

Vol 8 (1) ◽

Author(s):

Ulf Roland ◽

Frank Holzer ◽

Andreas Pöppl ◽

Frank-Dieter Kopinke

Keyword(s):

Electron Paramagnetic Resonance ◽

Thermal Plasma ◽

Pore Volume ◽

Structural Changes ◽

Peroxide Radical ◽

Paramagnetic Resonance ◽

Non Thermal Plasma ◽

The Impact ◽

Electron Paramagnetic ◽

Inner Pore

AbstractIn order to evaluate the potential of the combination of non-thermal plasma (NTP) and in situ heterogeous catalysis (plasma catalysis) for the improvement of efficiency and selectivity towards total oxidation of organic pollutants, the impact of plasma processes inside the inner pore volume of porous materials was investigated by means of catalytic reactions and spectroscopy. Besides studying the conversion of organic model substances, electron paramagnetic resonance (EPR) spectroscopy was applied to detect both the formation of radical species by the NTP and the initiation of structural changes to the catalyst. The presence of short-lived oxidizing species and plasma effects in the inner pore volume of porous catalysts (alumina in this case) could be clearly shown by detecting a significant influence on the oxidation process and the formation of a paramagnetic site which can be correlated to an aluminum peroxide radical: Al-O-O. The relatively stable paramagnetic center (lifetime > 14 days) was formed by the NTP independently of the gas atmosphere, namely its oxygen content. The signal was not significantly affected by the application of reducing agents to the sample.

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Anionic redox reactions and structural degradation in a cation-disordered rock-salt Li1.2Ti0.4Mn0.4O2 cathode material revealed by solid-state NMR and EPR

Journal of Materials Chemistry A ◽

10.1039/d0ta03358h ◽

2020 ◽

Vol 8 (32) ◽

pp. 16515-16526 ◽

Cited By ~ 2

Author(s):

Fushan Geng ◽

Bei Hu ◽

Chao Li ◽

Chong Zhao ◽

Olivier Lafon ◽

...

Keyword(s):

Electron Paramagnetic Resonance ◽

Solid State ◽

Rock Salt ◽

Epr Spectroscopy ◽

Solid State Nmr ◽

Redox Reactions ◽

Degradation Mechanism ◽

Structural Degradation ◽

Paramagnetic Resonance ◽

Electron Paramagnetic

The cation-disordered rock-salt Li1.2Ti0.4Mn0.4O2 is studied by solid-state NMR and electron paramagnetic resonance (EPR) spectroscopy during the first cycle. The anionic redox and structural degradation mechanism are discussed.

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Synthesis and Photocatalytic Mechanism of Visible Light-Activated LaVO4/TiO2 Composite

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.550-553.149 ◽

2012 ◽

Vol 550-553 ◽

pp. 149-152 ◽

Cited By ~ 1

Author(s):

Han Jie Huang ◽

Wen Long She ◽

Ling Wen Yang

Keyword(s):

Visible Light ◽

Diffuse Reflectance Spectroscopy ◽

Degradation Mechanism ◽

Active Oxygen Species ◽

X Ray Diffraction ◽

Paramagnetic Resonance ◽

Composite Photocatalyst ◽

X Ray ◽

Photocatalytic Degradation Mechanism ◽

Electron Paramagnetic

In this work, a visible light-activated LaVO4/TiO2 composite photocatalyst has been successfully synthesized via a facile coupled method. The composite was characterized by powder X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS) and spin-trapping electron paramagnetic resonance (EPR). Based on the detection of active oxygen species, a visible light-induced photocatalytic degradation mechanism of benzene on LaVO4/TiO2 was proposed.

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Ortho Isomeric Mn(III) N-Alkyl- and Alkoxyalkylpyridylporphyrins—Enhancers of Hyaluronan Degradation Induced by Ascorbate and Cupric Ions

International Journal of Molecular Sciences ◽

10.3390/ijms22168608 ◽

2021 ◽

Vol 22 (16) ◽

pp. 8608

Author(s):

Katarína Valachová ◽

Peter Rapta ◽

Nuno M. M. Moura ◽

Ines Batinic-Haberle ◽

Ladislav Šoltés

Keyword(s):

Degradation Kinetics ◽

Oxidative Degradation ◽

Physiological Solution ◽

Paramagnetic Resonance ◽

Redox Active ◽

Poor Outcomes ◽

The Impact ◽

Electron Paramagnetic ◽

Insight Into ◽

Biological Milieu

High levels of hyaluronic acid (HA) in tumors correlate with poor outcomes with several types of cancers due to HA-driven support of adhesion, migration and proliferation of cells. In this study we explored how to enhance the degradation of HA into low-molecular fragments, which cannot prevent the immune system to fight tumor proliferation and metastases. The physiological solution of HA was exposed to oxidative degradation by ascorbate and cupric ions in the presence of either one of three ortho isomeric Mn(III) substituted N-alkyl- and alkoxyalkylpyridylporphyrins or para isomeric Mn(III) N-methylpyridyl analog, commonly known as mimics of superoxide dismutase. The changes in hyaluronan degradation kinetics by four Mn(III) porphyrins were monitored by measuring the alteration in the dynamic viscosity of the HA solution. The ortho compounds MnTE-2-PyP5+ (BMX-010, AEOL10113), MnTnBuOE-2-PyP5+ (BMX-001) and MnTnHex-2-PyP5+ are able to redox cycle with ascorbate whereby producing H2O2 which is subsequently coupled with Cu(I) to produce the •OH radical essential for HA degradation. Conversely, with the para analog, MnTM-4-PyP5+, no catalysis of HA degradation was demonstrated, due to its inertness towards redox cycling with ascorbate. The impact of different Mn(III)-porphyrins on the HA decay was further clarified by electron paramagnetic resonance spectrometry. The ability to catalyze the degradation of HA in a biological milieu, in the presence of cupric ions and ascorbate under the conditions of high tumor oxidative stress provides further insight into the anticancer potential of redox-active ortho isomeric Mn(III) porphyrins.

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EPR and emission study of silicon suboxide nanopillars

MRS Proceedings ◽

10.1557/opl.2013.1163 ◽

2013 ◽

Vol 1617 ◽

pp. 51-56

Author(s):

V. Bratus’ ◽

I. Indutnyi ◽

P. Shepeliavyi ◽

T. Torchynska

Keyword(s):

Paramagnetic Resonance ◽

Sputtered Films ◽

Low Intensity ◽

Correlated Electron ◽

Silicon Suboxide ◽

Epr Signal ◽

Emission Study ◽

G Value ◽

The Impact ◽

Electron Paramagnetic

ABSTRACTThe results of correlated electron paramagnetic resonance (EPR) and photoluminescence (PL) study of obliquely deposited porous SiOxfilms after step-by-step 15 min annealing within 105 min in vacuum at 950°C are presented. The low intensity symmetrical and featureless EPR line with a g-value g=2.0044 and a linewidth of 0.77 mT has been detected in as-sputtered films and attributed to dangling bonds (DB) of silicon atoms in amorphous SiOxdomains withx=0.8. Successive annealing results in decreasing this line and the appearance of an intense EPR line with g=2.0025, linewidth of 0.11 mT and a hyperfine doublet with 1.6 mT splitting. According to the parameters this spectrum has been attributed to theEXcenter, a hole delocalized over four non-bridging oxygen atoms grouped around a Si vacancy in SiO2. The impact of chemical treatment before annealing and duration of anneals on the defect system, and a correlation of the PL intensity with decreasing of theDBEPR signal are discussed.

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Identifying the "true" repeat unit of a copolymer using time-resolved electron paramagnetic resonance spectroscopy: a case study involving PNDIT2, NDI-T2 and T-NDI-T

10.26434/chemrxiv-2022-jwv10 ◽

2022 ◽

Author(s):

Clemens Matt ◽

Rukiya Matsidik ◽

Deborah L. Meyer ◽

Mirjam Schröder ◽

Michael Sommer ◽

...

Keyword(s):

Electron Paramagnetic Resonance ◽

Electronic Structure ◽

Conjugated Polymers ◽

Organic Electronics ◽

Repeat Unit ◽

Paramagnetic Resonance ◽

Time Resolved ◽

Donor And Acceptor ◽

The Impact ◽

Electron Paramagnetic

Semiconducting polymers promise to revolutionise the way electronic devices can be built and deployed for a vast array of applications ranging from light-energy conversion to sensors to thermoelectric generators. Conjugated push-pull copolymers consisting of alternating donor and acceptor moieties are at the heart of these applications, due to the large tunability of their electronic structure. Hence, knowing the repeat unit and thus the chromophore of these materials is essential for a detailed understanding of the structure--function relationship of conjugated polymers used in organic electronics applications. Therefore, spectroscopic tools providing the necessary molecular resolution that allows to discriminate between different building blocks and to decide which one actually resembles the electronic structure of the polymer are of utmost importance. Time-resolved electron paramagnetic resonance (TREPR) spectroscopy is both, perfectly suited for this task and clearly superior to optical spectroscopy, particularly when supported by quantum-chemical calculations. This is due to its molecular resolution and unique capability of using light-induced triplet states to probe the electronic structure as well as the impact of the local environment. Here, we demonstrate the power of this approach for the polymer PNDIT2 (poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)}) revealing NDI-T2 unambiguously as the "true" repeat unit of the polymer, representing the chromophore. The alternative building block T-NDI-T has a markedly different electronic structure. These results are of high importance for the rational design of conjugated polymers for organic electronics applications.

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Reductive and Oxidative UV Degradation of PFAS—Status, Needs and Future Perspectives

Water ◽

10.3390/w13223185 ◽

2021 ◽

Vol 13 (22) ◽

pp. 3185

Author(s):

Muhammad Umar

Keyword(s):

Current Knowledge ◽

Critical Evaluation ◽

Future Perspectives ◽

Uv Degradation ◽

Water And Wastewater ◽

Polyfluoroalkyl Substances ◽

Restricted Use ◽

Background Ions ◽

The Impact ◽

By Products

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) consist of a group of environmentally persistent, toxic and bio-accumulative organic compounds of industrial origin that are widely present in water and wastewater. Despite restricted use due to current regulations on their use, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) remain the most commonly detected long-chain PFAS. This article reviews UV-based oxidative and reductive studies for the degradation of PFAS. Most of the UV-based processes studied at lab-scale include low pressure mercury lamps (emitting at 254 and 185 nm) with some studies using medium pressure mercury lamps (200–400 nm). A critical evaluation of the findings is made considering the degradation of PFAS, the impact of water quality conditions (pH, background ions, organics), types of oxidizing/reducing species, and source of irradiation with emphasis given to mechanisms of degradation and reaction by-products. Research gaps related to understanding of the factors influencing oxidative and reductive defluorination, impact of co-existing ions from the perspective of complexation with PFAS, and post-treatment toxicity are highlighted. The review also provides an overview of future perspectives regarding the challenges in relation to the current knowledge gaps, and future needs.

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The Impact of Hydrogenation on Structural and Superconducting Properties of FeTe0.65Se0.35 Single Crystals

Materials ◽

10.3390/ma14247900 ◽

2021 ◽

Vol 14 (24) ◽

pp. 7900

Author(s):

Stanislav I. Bondarenko ◽

Anatolij I. Prokhvatilov ◽

Roman Puźniak ◽

Jarosław Piętosa ◽

Andrey A. Prokhorov ◽

...

Keyword(s):

Magnetic Field ◽

Electron Paramagnetic Resonance ◽

Single Crystals ◽

Structural Changes ◽

Superconducting Transition ◽

Superconducting Properties ◽

Paramagnetic Resonance ◽

The Impact ◽

Electron Paramagnetic ◽

Diffusion Of Hydrogen

Properties of FeTe0.65Se0.35 single crystals, with the onset of critical temperature (Tconset) at 15.5 K, were modified via hydrogenation performed for 10–90 h, at temperatures ranging from 20 to 250 °C. It was found that the tetragonal matrix became unstable and crystal symmetry lowered for the samples hydrogenated already at 200 °C. However, matrix symmetry was not changed and the crystal was not destroyed after hydrogenation at 250 °C. Bulk Tcbulk, determined at the middle of the superconducting transition, which is equal to 12–13 K for the as grown FeTe0.65Se0.35, rose by more than 1 K after hydrogenation. The critical current density studied in magnetic field up to 70 kOe increased 4–30 times as a consequence of hydrogenation at 200 °C for 10 h. Electron paramagnetic resonance measurements also showed higher values of Tcbulk for hydrogenated crystals. Thermal diffusion of hydrogen into the crystals causes significant structural changes, leads to degeneration of crystal quality, and significantly alters superconducting properties. After hydrogenation, a strong correlation was noticed between the structural changes and changes in the parameters characterizing the superconducting state.

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