State Of Radical Research Articles

Effects of a redox-active diketone on the photochemical transformation of roxarsone: Mechanisms and environmental implications

Organoarsenical antibiotics pose a severe threat to the environment and human health. In aquatic environment, dissolved organic matter (DOM)-mediated photochemical transformation is one of the main processes in the fate of organoarsenics. Dicarbonyl is a typical redox-active moiety in DOM. However, the knowledge on the photoconversion of organoarsenics by DOM, especially the contributions of dicarbonyl moieties is still limited. Here, we systematically investigated the photochemical transformation of three organoarsenics with the simplest β-diketone, acetylacetone (AcAc), as a model dicarbonyl moiety of DOM. The presence of AcAc significantly enhanced the photochemical conversion of roxarsone (ROX), whereas only minor effects were observed for 3-amino-4-hydroxyphenylarsonic acid (HAPA) and arsanilic acid (ASA), because the latter two (with an amino (-NH2) group) are more photoactive than ROX (with a nitro (-NO2) group). The results demonstrate that AcAc was a potent photo-activator and the reduction of –NO2 to –NH2 might be a rate-limiting step in the phototransformation of ROX. At a 1:1 M ratio of AcAc to ROX, the photochemical transformation rate of ROX was increased by 7 folds. In O2-rich environment, singlet oxygen, peroxide radicals, and ·OH were the main reactive species that led to the breakage of the C–As bond in ROX and the oxidation of the released arsono group to arsenate, whereas the triplet-excited state of AcAc (3AcAc*) and carbon-centered radicals from the photolysis of AcAc dominated in the reductive transformation of ROX. In anoxic environment, 3-amino-4-hydroxyphenylarsonic acid was one of the main reductive transformation intermediates of ROX, whose photolysis rate was about 35 times that of ROX. The knowledge obtained here is of great significance to better understand the fate of organoarsenics in natural environment.

Probing the Strong Nonadiabatic Interactions in the Triazolyl Radical Using Photodetachment Spectroscopy and Resonant Photoelectron Imaging of Cryogenically Cooled Anions.

Although the adiabatic potential energy surfaces defined by the Born-Oppenheimer approximation are the cornerstones for understanding the electronic structure and spectroscopy of molecular systems, nonadiabatic effects due to the coupling of electronic states by nuclear motions are common in complex molecular systems. The nonadiabatic effects were so strong in the 1,2,3-triazolyl radical (C2H2N3) that the photoelectron spectrum of the triazolide anion was rendered unassignable and could only be understood using nonadiabatic calculations, involving the four low-lying electronic states of triazolyl. Using photodetachment spectroscopy and resonant photoelectron imaging of cryogenically cooled anions, we are able to completely unravel the complex vibronic levels of the triazolyl radical. Photodetachment spectroscopy reveals a dipole-bound state for the triazolide anion at 172 cm-1 below the detachment threshold and 32 vibrational Feshbach resonances. Resonant photoelectron imaging is conducted by tuning the detachment laser to each of the Feshbach resonances. Combining the photodetachment spectrum and the resonant photoelectron spectra, we are able to assign all 28 vibronic peaks resolved for the triazolyl radical. Fundamental frequencies for 12 vibrational modes of the ground state of the triazolyl radical are measured experimentally. The current study provides unprecedented experimental vibronic information, which will be valuable to verify theoretical models to treat nonadiabatic effects involving multiple electronic states.

A DFT and SERS study of synergistic roles of thermodynamics and kinetics during the electrocatalytic reduction of benzyl chloride at silver cathodes

The reductive cleavage of carbon-halogen bonds is one of the classical model systems of concerted versus non-concerted bond breaking electron transfer in molecular electrochemistry, but most studies did not consider the influence of adsorption of reaction intermediates on this phenomenon. We performed density functional theory (DFT) calculations to understand the electrochemical reduction of benzyl chloride at silver electrodes through predicting the surface adsorption effect of the reactant and of follow-up intermediates and analyzing the energetics of the overall dissociative electron transfer. The ensuing DFT calculations of surface-enhanced Raman spectroscopic (SERS) signals provided some key information for characterizing different surface species at different potentials at the molecular level. The most intense and broad spectral peak observed near 800 cm−1 in the electrochemical SERS was thus assigned to the CH2 wagging vibration closely associated with the co-adsorption of benzyl radical and chlorine. After the dissociation of the C-Cl benzyl chloride bond, the chloride anion adsorbs at the three-fold hollow site on silver electrodes, as indicated by a low vibrational frequency and a weak Raman signal. Conversely, the formed benzyl radical intermediate is found to adsorb at the top site with the characteristic vibrational frequency and strong Raman intensity. DFT calculations further confirmed that the kinetic effect underlying the electrocatalytic activity of silver electrodes is closely associated with the intrinsic energy barrier and the dissociative adsorption state of benzyl radical and chlorine on silver electrodes. Finally, we discuss the fundamental meaning of the kinetic rate constant of the first-step dissociative electron transfer for benzyl chloride on silver electrodes based on the different electron transfer models, indicating the synergistic roles of thermodynamics and kinetics.

Effect of disinfection on the photoreactivity of effluent organic matter and photodegradation of organic contaminants

Chlorine, UV254, and ozone are three typical processes commonly used for wastewater disinfection, which could change the photoreactivity of dissolved organic matter (DOM) in effluents of wastewater treatment plants (WWTPs). The photoinduced reactive species (RS) from DOM, primarily including the excited triplet state of DOM (3DOM*), singlet oxygen (1O2), and hydroxyl radical (•OH), play important roles in the attenuation of contaminants. However, the effect of disinfection processes on the photosensitized degradation of contaminants is poorly understood. This paper presents the first evidence that 3DOM*, 1O2, and •OH interaction with three typical contaminants (diphenhydramine, cimetidine, and N,N-diethyl-m-toluamide (DEET)) was largely impacted by DOM after disinfection. The results of electron spin resonance (ESR) spectrometry and laser flash photolysis (LFP) experiments demonstrated that the chlorination increased the formation rate of 3DOM* and 1O2, while UV254 irradiation and ozonation decreased the formation rate of these RS. All these three disinfection processes promoted the photoproduction of •OH and increased the photodegradation rate constants (kobs) of DEET by 26−361%. The kobs of diphenhydramine, cimetidine, and DEET correlated positively with the formation rate of 3DOM*, 1O2, and •OH, respectively. The bimolecular reaction rate constant of 3DOM* with diphenhydramine increased by ∼41% after chlorination. These findings suggest that disinfection processes altered the photogeneration of RS from DOM, which significantly impacts the fate of trace pollutants in aquatic environments.

Reaction of Methylidyne with Ethane: The C–C Insertion Is Unimportant

High-accuracy coupled-cluster calculations in combination with the E,J-resolved master-equation analysis are used to study the reaction mechanism and kinetics of methylidyne with ethane. This reaction plays an important role in the combustion of hydrocarbon fuels and in interstellar chemistry. Two distinct mechanisms, the C-C and the C-H insertions of CH in C2H6, are characterized. The C-C insertion pathway is identified to have a large barrier of 34.5 kcal mol-1 and hence plays no significant role in kinetics. The C-H insertion pathway is found to have no barrier, leading to a highly vibrationally excited n-C3H7 radical, which rapidly dissociates (within 50 ps) to yield CH3 + C2H4 and H + C3H6 in a roughly 7:3 ratio. These findings are in good agreement with an experimental result that indicates that about 20% of the reaction goes to H + C3H6. The reaction of the electronically excited quartet state of the CH radical with C2H6 is examined for the first time and found to proceed as a direct H-abstraction via a small barrier of 0.4 kcal mol-1 to yield triplet CH2 and C2H5. The reaction on the quartet state surface is negligibly slow at low temperatures characteristic of interstellar environments but becomes important at high combustion temperatures.

Contrasting Impacts of Photochemical and Microbial Processing on the Photoreactivity of Dissolved Organic Matter in an Adirondack Lake Watershed.

Photochemical and microbial processing are the prevailing mechanisms that shape the composition and reactivity of dissolved organic matter (DOM); however, prior research has not comparatively evaluated the impacts of these processes on the photoproduction of reactive intermediates (RIs) from freshly sourced terrestrial DOM. We performed controlled irradiation and incubation experiments with leaf and soil samples collected from an acid-impacted lake watershed in the Adirondack Mountain region of New York to examine the effects of DOM processing on the apparent quantum yields of RIs (Φapp,RI), including excited triplet states of DOM (3DOM*), singlet oxygen (1O2), and hydroxyl radicals (•OH). Photodegradation led to net reductions in Φapp,1O2, Φapp,3DOM*, and Φapp,•OH, whereas (photo-)biodegradation resulted in increases in Φapp,1O2 and Φapp,3DOM*. Photodegradation and (photo-)biodegradation also shifted the energy distribution of 3DOM* in different directions. Multivariate statistical analyses revealed the potential relevance of photo-biodegradation in driving changes in Φapp,1O2 and Φapp,3DOM* and prioritized five bulk DOM optical and redox properties that best explained the variations in Φapp,1O2 and Φapp,3DOM* along the watershed terrestrial-aquatic continuum. Our findings highlight the contrasting impacts of photochemical and microbial processes on the photoreactivity of freshly sourced terrestrial DOM and invite further studies to develop a more holistic understanding of their implications for aquatic photochemistry.

In vitro Assessment of Antioxidant and Anticancer Potential of Flavonoid Glycosides of Glinus oppositifolius (L.) Aug. DC.

Development of unbalanced state of free radicals and their elimination in the body is the reason for increase in different types of chronic diseases including cancer. A better natural supplement to play role of antioxidants to combat the free radicals and to reduce the risk of cancer is in high demand. This current research work focused on identifying such a potent phytocompounds from Glinus oppositifolius (L.) Aug. DC. The active compounds of the aerial parts of the plant have been extracted using methanol and the phytochemical analysis was carried out using qualitative tests, FTIR and GC-MS. The plant extract found to contain range of phyto compounds with good amounts of flavonoid and xylofuranoside. Flavonoid glycoside from the plant extract has been partially purified through chromatography and tested for efficiency against free radicals through in vitro antioxidant assays. The partially purified compound showed good antioxidant activity equivalent to 62.12 to 63.35 μg of rutin standard. Further cytotoxic nature of the flavonoid glycoside was also assessed against breast cancer MDA-MB-231 cell line. The tested compound has shown cancerous cell controlling ability (76.68% cell death in 24 h). The immense antioxidant and anticancer potential of flavonoid glycosides of G. oppositifolius could be utilized as a good source of natural, antioxidant supplement under nutraceuticals to prevent oxidative-stress-related disorders and also as therapeutic compound to cure cancer under pharmaceuticals.

Amoeba: Automated Molecular Excitation Bayesian Line-fitting Algorithm

Abstract The hyperfine transitions of the ground-rotational state of the hydroxyl radical (OH) have emerged as a versatile tracer of the diffuse molecular interstellar medium. We present a novel automated Gaussian decomposition algorithm designed specifically for the analysis of the paired on-source and off-source optical depth and emission spectra of these OH transitions. In contrast to existing automated Gaussian decomposition algorithms, Amoeba (Automated Molecular Excitation Bayesian line-fitting Algorithm) employs a Bayesian approach to model selection, fitting all four optical-depth and four emission spectra simultaneously. Amoeba assumes that a given spectral feature can be described by a single centroid velocity and full width at half maximum, with peak values in the individual optical-depth and emission spectra then described uniquely by the column density in each of the four levels of the ground-rotational state, thus naturally including the real physical constraints on these parameters. Additionally, the Bayesian approach includes informed priors on individual parameters that the user can modify to suit different data sets. Here we describe Amoeba and establish its validity and reliability in identifying and fitting synthetic spectra with known (but hidden) parameters, finding that the code performs very well in a series of practical tests. Amoeba’s core algorithm could be adapted to the analysis of other species with multiple transitions interconnecting shared levels (e.g., the 700 MHz lines of the first excited rotational state of CH). Users are encouraged to adapt and modify Amoeba to suit their own use cases.

Photoionisation of the CH radical using the B-spline R-matrix method

Aims. The primary motivation for this paper is to provide accurate data for the photoionisation of the CH radical, including the absolute total photoionisation cross-section, partial cross-sections, and photoelectron angular distribution. In addition, the near threshold features in the photoionisation curve (which are absent in previous studies) are produced with high precision. Methods. A multichannel wavefunction based on the R-matrix approach, which uses the configuration interaction (CI) method to describe electronic correlation, is carried out in the present calculations. A set of B-spline orbitals is employed to represent the accurate continuum. The distinctive feature of the present calculations allows us to generate a more accurate description of the bound and continuum states than those employed before. Results. Total photoionisation cross-sections from the ground state of CH radicals and partial cross-sections corresponding to 1π, 3σ, and 2σ states of CH+ ions are presented for photon energies ranging from threshold to 80 eV. Extensive resonance structures, which are absent in previous studies, are observed for the first time near the ionisation threshold. The cross-section dataset obtained from the present calculations is expected to be sufficiently accurate and comprehensive for most current modelling applications involving the photon and CH radical scattering system.

Distribution of H^upbeta Hyperfine Couplings in a Tyrosyl Radical Revealed by 263 GHz ENDOR Spectroscopy

^1H ENDOR spectra of tyrosyl radicals (Y^bullet) have been the subject of numerous EPR spectroscopic studies due to their importance in biology. Nevertheless, assignment of all internal ^1H hyperfine couplings has been challenging because of substantial spectral overlap. Recently, using 263 GHz ENDOR in conjunction with statistical analysis, we could identify the signature of the H^{upbeta _2} coupling in the essential Y_{122} radical of Escherichia coli ribonucleotide reductase, and modeled it with a distribution of radical conformations. Here, we demonstrate that this analysis can be extended to the full-width ^1H ENDOR spectra that contain the larger H^{upbeta _1} coupling. The H^{upbeta _2} and H^{upbeta _1} couplings are related to each other through the ring dihedral and report on the amino acid conformation. The 263 GHz ENDOR data, acquired in batches instead of averaging, and data processing by a new “drift model” allow reconstructing the ENDOR spectra with statistically meaningful confidence intervals and separating them from baseline distortions. Spectral simulations using a distribution of ring dihedral angles confirm the presence of a conformational distribution, consistent with the previous analysis of the H^{upbeta _2} coupling. The analysis was corroborated by 94 GHz ^2H ENDOR of deuterated Y_{122}^bullet. These studies provide a starting point to investigate low populated states of tyrosyl radicals in greater detail.

SOMO-HOMO Conversion in Triplet Cyclopentane-1,3-diyl Diradicals.

According to the Aufbau principle, singly occupied molecular orbitals (SOMOs) are energetically higher lying than a highest doubly occupied molecular orbital (HOMO) in the electronically ground state of radicals. However, in the last decade, SOMO–HOMO-converted species have been reported in a limited group of radicals, such as distonic anion radicals and nitroxides. In this study, SOMO–HOMO conversion was observed in triplet 2,2-difluorocyclopentane-1,3-diyl diradicals DR3F1, DR4F1, and 2-fluorocyclopentante-1,3-diyl diradical DR3HF1, which contain the anthracyl unit at the remote position. The high HOMO energy in the anthracyl moiety and the low-lying SOMO–1 due to the fluoro-substituent effect are the key to the SOMO–HOMO conversion phenomenon. Furthermore, the cation radical DR3F1+ generated through the one-electron oxidation of DR3F1 was found to be a SOMO–HOMO-converted monoradical.

Density functional theory calculation of the Renner–Teller effect in NCO: Preliminary assessment of exact exchange energy on the accuracy of the Renner coefficient

AbstractAssessment of DFT methods through analysis of the Renner–Teller effect (RTE) in the state of the NCO radical was completed. Our results suggest that the amount of exact exchange at long range is important for an accurate description of the RTE in NCO. DFT functionals from the B3LYP, PBE, TPSS, M06, and M11 families with standard Correlation Consistent, 6‐311G split valence family, as well as Sadlej, and Sapporo polarized triple‐ζ basis sets were assessed. Our Renner coefficients are compared with previously published theoretical and experimental results to characterize the overall accuracy of various functional/basis set combinations in determining the RTE splitting in the (bending) modes of . We suggest that this method of analysis can be extended to other systems, serve as an accuracy metric when selecting a functional, and provide a means to create training sets for machine learning in computational molecular physics applications.

Threshold Photoelectron Spectroscopy of the CH2I, CHI, and CI Radicals.

VUV photoionization of the CHnI radicals (with n = 0, 1, and 2) is investigated by means of synchrotron radiation coupled with a double imaging photoion-photoelectron coincidence spectrometer. Photoionization efficiencies and threshold photoelectron spectra (TPES) for photon energies ranging between 9.2 and 12.0 eV are reported. An adiabatic ionization energy (AIE) of 8.334 ± 0.005 eV is obtained for CH2I, which is in good agreement with previous results [8.333 ± 0.015 eV, SztárayJ. Chem. Phys.2017, 147, 01394428688391], while for CI an AIE of 8.374 ± 0.005 eV is measured for the first time and a value of ∼8.8 eV is estimated for CHI. Ab initio calculations have been carried out for the ground state of the CH2I radical and for the ground state and excited states of the radical cation CH2I+, including potential energy curves along the C–I coordinate. Franck–Condon factors are calculated for transitions from the CH2I(X̃2B1) ground state of the neutral radical to the ground state and excited states of the radical cation. The TPES measured for the CH2I radical shows several structures that correspond to the photoionization into excited states of the radical cation and are fully assigned on the basis of the calculations. The TPES obtained for the CHI is characterized by a broad structure peaking at 9.335 eV, which could be due to the photoionization from both the singlet and the triplet states and into one or more electronic states of the cation. A vibrational progression is clearly observed in the TPES for the CI radical and a frequency for the C–I stretching mode of 760 ± 60 cm–1 characterizing the CI+ electronic ground state has been extracted.

Properties of transitions between X3Σ–, A3Π, a1Δ, b1Σ+, and c1Π states of NH radicals

Properties of the transitions between Ω states originating from the X3Σ–, A3Π, a1Δ, b1Σ+, and c1Π states of NH were investigated herein. The radiative lifetimes of the A3Π state were 0.42, 0.43, 0.44, 0.50, 0.58, 0.70, 0.90, and 1.45 μs for the υ = 0 – 7 levels; and those of the c1Π state were 0.44, 0.54, and 0.72 μs for υ = 0 – 2, respectively. The radiative lifetimes of the A3Π2 state were 0.48, 0.53, 0.60, 0.68, 0.79, 0.95, 1.21, and 1.95 μs for υ = 0 – 2, respectively, which are slightly larger than those of the A3Π state for same υ. The radiative lifetimes of the A3Π2 state were almost the same as those of the A3Π0+ and A3Π0– states. The radiative lifetimes of the A3Π2, A3Π0+, and A3Π0– states were slightly larger than those of the A3Π1 state. The radiative lifetimes of the first 16 levels of the a1Δ2 state varied from 2.4 to 432.8 s. Those of the b1Σ+0+ state were between 0.3 and 72 ms. Those of the c1Π1 state were determined as approximately 0.44, 0.54, and 0.72 μs for υ = 0 – 2, respectively. The radiative lifetimes calculated herein compared well with the available experimental results. The Franck–Condon factors and Einstein A coefficients of all possible transitions were calculated. The results reported herein provide useful guidelines for future investigations, both experimental and theoretical.

Mechanistic Investigation of Enhanced Photoreactivity of Dissolved Organic Matter after Chlorination.

Chlorine is commonly used in disinfection processes in wastewater treatment plants prior to discharge of the effluents into receiving waters. Effluent organic matter and humic substances constitute up to 90% of dissolved organic matter (DOM) in receiving water, which induces photogeneration of reactive species (RS) such as excited triplet state of DOM (3DOM*), singlet oxygen (1O2), and hydroxyl radical (•OH). The RS plays an important role in the attenuation of trace pollutants. However, the effect of chlorine disinfection on the photoreactivity of the DOM has remained unclear. Here, we investigated the physicochemical properties and subsequent RS variation after chlorination of DOM. Solid-state 13C cross-polarization/magic angle-spinning NMR and Fourier transform ion cyclotron resonance mass spectrometry verified that the aromaticity, electron-donating capacity (EDC), and average molecular weight of DOM decreased markedly after chlorination. It was found for the first time that the photoproduction of 3DOM*, 1O2, and •OH increased markedly after chlorination of DOM upon irradiation of simulated sunlight. The quantum yields of 3DOM*, 1O2, and •OH were positively correlated with E2/E3 (ratio of the absorbance at 254 to 365 nm) while negatively correlated with EDC before and after chlorination. These findings highlight the synergetic effect of chlorine disinfection on the photosensitization of DOM under irradiation of sunlight, which will promote the removal of trace pollutants in surface waters.

Photo-oxidation of arsenite in acidic waters containing Suwannee River fulvic acid: roles of 3SRFA* and hydroxyl radical.

The photo-oxidation of arsenite (As(III)) in solution containing Suwannee River fulvic acid (SRFA) under the ultraviolet A (UVA) irradiation (λmax = 365 nm) was studied. In a solution containing 100.0 μg·L-1 As(III) and 10.0 mg·L-1 SRFA at pH 3.0, SRFA induced As(III) photo-oxidation by producing the triplet excited state of SRFA (3SRFA*) and hydroxyl radical(HO˙). Approximately 82% of As(III) oxidation was attributed to HO˙ which depended strongly on HO2˙/O2˙-. The remaining 18% of As(III) oxidation was attributed to the direct reaction between As(III) and 3SRFA*. The photo-oxidation of As(III) was significantly affected by solution pH. Excess SRFA inhibited As(III) photo-oxidation. The addition of a low concentration of ferric ions retarded the photo-oxidation of As(III) due to the poor photo-activity of Fe(III)-SRFA complexes. In contrast, the addition of ferric ions at high concentration greatly accelerated As(III) photo-oxidation because of the high photo-activity of Fe(III)-OH complexes. The fractions of SRFA with different molecular weight showed different oxidizing capacities under UV irradiation which was possibly related to the different contents of phenolic OH groups. The findings have important environmental implications for the photo-transformation behavior of As(III) in natural surface waters containing dissolved organic matter, especially acidic waters.

Accurate quantum dynamics simulation of the photodetachment spectrum of the nitrate anion (NO3 -) based on an artificial neural network diabatic potential model.

The photodetachment spectrum of the nitrate anion (NO3 -) is simulated from first principles using wavepacket quantum dynamics propagation and a newly developed accurate full-dimensional fully coupled five state diabatic potential model. This model utilizes the recently proposed complete nuclear permutation inversion invariant artificial neural network diabatization technique [D. M. G. Williams and W. Eisfeld, J. Phys. Chem. A 124, 7608 (2020)]. The quantum dynamics simulations are designed such that temperature effects and the impact of near threshold detachment are taken into account. Thus, the two available experiments at high temperature and at cryogenic temperature using the slow electron velocity-map imaging technique can be reproduced in very good agreement. These results clearly show the relevance of hot bands and vibronic coupling between the X̃ 2A2 ' ground state and the B̃ 2E' excited state of the neutral radical. This together with the recent experiment at low temperature gives further support for the proper assignment of the ν3 fundamental, which has been debated for many years. An assignment of a not yet discussed hot band line is also proposed.

Laser-Induced Fluorescence Spectroscopy of Large Secondary Alkoxy Radicals: Part II. Rotational and Fine Structure.

Selected vibronic bands of the B̃ ← X̃ laser-induced fluorescence (LIF) spectra of jet-cooled 2-pentoxy and 2-hexoxy, including the origin and CO-stretch bands, have been measured with rotational resolution and analyzed using (1) an effective Hamiltonian that comprises a rotational part and a spin-rotation (SR) part (the "isolated-states model") and (2) a recently developed Hamiltonian in which the nearly degenerate à and X̃ states are treated together (the "coupled-states model") (see Liu, J., J. Chem. Phys. 2018, 148, 124112). The observed rotational and fine structures of the strongest vibronic bands have first been simulated using a genetic algorithm with the isolated-states model. The parameters for the simulation include rotational constants for both the X̃ and B̃ states, which can be calculated from the electronic structure theory, as well as the electronic SR constants of the X̃ state and the transition dipole moments (TDMs), both of which are predicted based on their transferability in an "orbital-fixed coordinate system" using iso-propoxy as the reference molecule. Quantum chemistry calculations suggest that the lowest two electronic (X̃ and Ã) states of secondary alkoxy radicals have small energy separations on the order of 100 cm-1 (see Part I of this series: J. Phys. Chem. A 2021, DOI: 10.1021/acs.jpca.0c10662). The electron configurations of these two nearly degenerate states have been determined by comparing the experimentally determined rotational constants and the TDMs to the ones predicted for the X̃ and à states. The experimental LIF spectra were also simulated with the coupled-states model, in which the effective spin-orbit (SO) constants (aζed) and the SO-free separation between the à and the X̃ states (ΔE0) have been determined. Molecular constants derived from fitting the rotational and fine structures of the experimental LIF spectra enabled unambiguous assignment of the observed vibronic bands to specific conformers of 2-pentoxy and 2-hexoxy as reported in Part I.

Effect of UV/chlorine treatment on photophysical and photochemical properties of dissolved organic matter

Dissolved organic matter (DOM) is a ubiquitous component in effluents, DOM discharged with an effluent can affect the composition and properties of natural DOM in the receiving waters. As the photophysical and photochemical properties of effluent DOM can be changed by wastewater treatment processes, the effect of UV/chlorine treatment on the photophysical and photochemical properties of DOM was investigated using Suwannee River fulvic acid (SRFA) and Suwannee River natural organic matter (SRNOM) as representatives. Results showed that the absorbance of the two DOM was significantly decreased. The evolution trends of three representative photophysical parameters upon increase of chlorine dosages were observed. Also, a decrease in DOM aromaticity, molecular weight and electron-donating capacity was observed upon increasing chlorine dosage. Quantum yields of excited triplet state of DOM (3DOM*), singlet oxygen (1O2) and hydroxyl radicals (·OH) first decreases and then increased in the UV/chlorine systems upon increasing chlorine dosages due to the different reaction pathways of the two DOM. Moreover, 3DOM* can not only be regarded as a “controller” of other reactive intermediates, but also effectively promote the photodegradation of bezafibrate, which is classified as a persistent organic contaminant. This study gives deep insights into effects of UV/chlorine on the photophysical and photochemical properties of DOM, and is helpful for understanding the dynamic roles of DOM in the photodegradation of micropollutants.

Urotensin-II, oxidative stress, and inflammation increase in hypertensive and resistant hypertensive patients

ABSTRACT Objective: Hypertension is a multi-factorial process prevalent in developed as well as in developing countries. Urotensin-II, different antioxidants, free radicals, and inflammatory biomarkers play an essential role in the cardiovascular system. The aim of this study is to investigate Urotensin-II, oxidative stress, and inflammation markers in normotensive, hypertensive, and resistant hypertensive patients. Methods: Fifty resistance hypertensive (rHT) patients, 50 hypertensive patients, and 50 age gender matched normotensive controls (NT-control) were enrolled. Urotensin-II (UII), total oxidant status (TOS), total antioxidant status (TAS), native thiol (NT), total thiol (TT), disulfide (DIS), interleukin 1 beta (IL1β), interleukin 6 (IL6), tumor necrosis factor-alpha (TNFα), high sensitive c reactive protein (hsCRP), high-density lipoprotein (HDL) low-density lipoprotein (LDL), and total cholesterol (TC) were evaluated. Results: Serum levels of UII, IL1β, IL6, TNFα, DIS, TOS, and OSI were found higher in rHT and HT as compared to NT-control (p < .001). On the contrary, serum levels of TT, TAS, and NT were lower in rHT and HT as compared to NT-control (p < .001). While TC, hsCRP, TOS, OSI, UII, IL1β, IL6, and TNFα levels increase from HT to rHT group (p < .001); TAS and NT levels decrease from HT to rHT group (p < .001). Conclusions: UII levels, oxidative stress, and inflammation are higher in rHT and HT, while antioxidants and thiol levels are lower than the NT-control. Our study clearly showed that rHT and HT are more susceptible to impaired states of antioxidants, oxidative stress, and free radicals.