Photodegradation of acetochlor in water and UV photoproducts identified by mass spectrometry

The sunlight photodegradation half-lives of 20 mg/L acetochlor were 151, 154 and 169 days in de-ionized water, river water and paddy water, respectively. When exposed to ultraviolet (UV) light, acetochlor in aqueous solution was rapidly degraded. The half-lives were 7.1, 10.1, and 11.5 min in de-ionized water, river water and paddy water, respectively. Photoproducts of acetochlor were identified by gas chromatography/mass spectrometry(GC/MS) and found at least twelve photoproducts resulted from dechlorination with subsequent hydroxylation and cyclization processes. The chemical structures of ten photoproducts were presumed on the basis of mass spectrum interpretation and literature data. Photoproducts are identified as 2-ethyl-6-methylaniline; N,N-diethylaniline; 4,8-dimethyl-2-oxo-1,2,3,4- tetrahydroquino-line; 2-oxo-N-(2-ethyl-6-methylphenyl)-N-(ethoxymethyl)acetamide; N-(ethoxymethyl)-2′-ethyl-6′-methylformanilide;1-hydroxyacetyl-2-ethoxyl-7-ethylind ole; 8-ethyl-1-ethoxymethyl-2-oxo-1,2,3,4-tetrahydroquinoline; 4,8-dimethyl-1-ethoxymethyl-2-oxo-1,2,3,4-tetrahydroquinoline; 2-hydroxy-2′-ethyl-6′-methyl-N-(ethoxymethyl)acetanilide and a compound related to acetochlor. The other two photoproducts were detected by GC/MS although their chemical structure was unknown.

Photodegradation of Atorvastatin under Light Conditions Relevant to Natural Waters and Photoproducts Toxicity Assessment

Atorvastatin, widely prescribed hypolipidemic drug, undergoes rapid, probably self-sensitised, degradation (less than 20% left after 25-minute irradiation) if irradiated by wavelengths 300 - 350 nm in aqueous solution. When ferric ions are added to the reaction mixture, the degradation follows first order kinetics with a rate constant of 0.130 min−1. Photochemical degradation may thus represent a significant way of environmental transformation of this pharmaceutical. Toxicity testing of atorvastatin and atorvastatin photoproducts performed on the water plant Lemna minor revealed that atorvastatin itself exhibited no observable toxic effect measured as leaf area growth inhibition, while the photoproducts showed a significant toxicity to the plant, which shows the extreme importance of investigating not only toxicity of drugs themselves on aquatic organisms but also effects of their transformation products.

Photoproducts of tetracycline and oxytetracycline involving self-sensitized oxidation in aqueous solutions:Effects of Ca^(2+) and Mg^(2+)

Tetracyclines constitute one of the most important antibiotic families and represent a classic example of phototoxicity. The photoproducts of tetracyclines and their parent compounds have potentially adverse effects on natural ecosystem. In this study, the self-sensitized oxidation products of tetracycline （TC） and oxytetracycline （OTC） were determined and the effects of Ca2＋ and Mg2＋on self-sensitized degradation were investigated. The Ca2＋ and Mg2＋ in the natural water sample accounted for enhancement （pH 7.3） and inhibition （pH 9.0） of photodegradation of TC and OTC due to the formation of metal-ions complexes. The formation of Mg2＋ complexes was unfavorable for the photodegradation of the tetracyclines at both pH values. In contrast, the Ca2＋ complexes facilitated the attack of singlet oxygen （102） arising from self-sensitization at pH 7.3 and enhanced TC photodegradation. For the first time, self- sensitized oxidation products of TC and OTC were verified by quenching experiments and detected by LC/ESI-DAD-MS. The products had a nominal mass 14 Da higher than the parent drugs （designated M＋ 14）, which resulted from the 102 attack of the dimethylamino group on the C-4 atom of the tetracyclines. The presence of Ca2＋ and Mg2＋ also affected the generation of M＋ 14 due to the formation of metal-ions complexes with TC and OTC. The findings suggest that the metal-ion complexation has significant impact on the self- sensitized oxidation processes and the photoproducts of tetracyclines.

Effects of temperature on UV-B-induced DNA damage and photorepair in Arabidopsis thaliana

DNA damage in the form of cyclobutane pyrimidine dimers(CPDs) and (6-4) photoproducts(6-4PPs) induced by UV-B radiation in Arabidopsis thaliana at different temperatures was investigated using ELISA with specific monoclonal antibodies. CPDs and 6-4PPs increased during 3 h UV-B exposure, but further exposure led to decreases. Contrary to the commonly accepted view that DNA damage induced by UV-B radiation is temperature-independent because of its photochemical nature, we found UV-B-induction of CPDs and 6-4PPs in Arabidopsis to be slower at a low than at a high temperature. Photorepair of CPDs at 24℃ was much faster than that at 0℃ and 12℃, with 50% CPDs removal during 1 h exposure to white light. Photorepair of 6-4PPs at 12℃ was very slow as compared with that at 24℃, and almost no removal of 6-4PPs was detected after 4 h exposure to white light at 0℃. There was evidence to suggest that temperature-dependent DNA damage and photorepair could have important ecological implications.

Hydrolysis and Photolysis of Herbicide Clomazone in Aqueous Solutions and Natural Water Under Abiotic Conditions

The hydrolysis and photolysis of clomazone in aqueous solutions and natural water were assessed under natural and controlled conditions. Kinetics of hydrolysis and photolysis of clomazone were determined by HPLC-DAD. Photoproducts were identiifed by HPLC-MS. No noticeable hydrolysis occurred in aqueous buffer solutions （（25±2）°C, pH （4.5±0.1）, pH （7.4±0.1）, pH （9.0±0.1）;（50±2）°C, pH （4.5±0.1）, pH （7.4±0.1）） or in natural water up to 90 d. At pH （9.0±0.1） and （50±2）°C the half-life of clomazone was 50.2 d. Clomazone photodecomposition rate in aqueous solutions under UV radiation and natural sunlight followed ifrst-order kinetics. Degradation rates were faster under UV light （half-life of 51-59 min） compared to sunlight （half-life of 87-136 d）. Under UV light, four major photoproducts were detected and tentatively identiifed according to HPLC-MS spectral information such as 2-chlorobenzamide, N-hydroxy-（2-benzyl）-2-methylpropan-amide, 2-[2-phenol]-4,4-dimethyl-3-isoxazolidinone and 2-[（4,6-dihydroxyl-2-chlorine phenol）]-4,4-dimethyl-3-isoxazolidinone. These results suggested that clomazone photodegradation proceeds via several reaction pathways：1） dehalogenation;2） substitution of chlorine group by hydroxyl;3） cleavage of the side chain. Photosensitizers, such as H2O2 and ribolfavin, could enhance photolysis of clomazone in natural sunlight. In summary, we found that photoreaction is an important dissipation pathway of clomazone in natural water systems.

Qualitative Determination of Photodegradation Products of Progesterone and Testosterone in Aqueous Solution

Direct photochemical degradations of progesterone (PR) and testosterone (TR), two naturally produced hormones, have been conducted in non-buffered aqueous solution (pH ranging between 5.5 and 6.0). The irradiation experiments were carried out in a batch reactor upon monochromatic (254 nm) and polychromatic (λ > 290 nm) at 25°C. GLC/MS and LC/UV-DAD/MS analyses were performed to investigate phototransformation products after a solid phase extraction (SPE) step for analytes concentration. For each compound several by-products have been identified and are the same ones under both irradiation conditions. Because of the presence of the same chromophore (α, β-unsaturated group) absorbing UV radiations in both hormones, the majority of chromatographic peaks correspond to by-products formed according to identical mechanisms involving isomerization, enolization, oxidation and hydration to lead to the generation of lumiketone, cyclopentenone, spiro-hydration, oxidation and hydroxylation photoproducts.

Strange Meson Radiative Capture on the Proton in Low Energy QCD Lagrangian

Based on our low energy QCD Lagrangian description of strange meson photoproduction off the protonand the crossing symmetry, the strange meson radiative capture on the proton, K- + p →γ + A, is investigated in the[SUsF (6) O(3)]sym. SUc (3) quark model of baryon structure with the same input parameter, the only strong couplingconstant aM, as that in the strange meson photoproduction off the proton γ + p → K+ + A, a crossing channel of thecapture reaction. A good agreement on the branching ratio between the predictions and data is obtained successfully.This excellent fit indicates that our low energy QCD Lagrangian theory with only one free parameter is an advancedand unified description of strange meson photoproduction and its associated radiative capture.

HYDROGEN PHOTOPRODUCTION OF A.VARIABILIS INCORPORATED IN A PHOTOBIOREACTOR

H2 photoproduction and nitrogenase activities in two strains of Anabaena variabilismarked wild type ATCC 29413 and mutant PK84 exposed to thermal stress (temperature higher than thenormal incubation temperature of 30℃) were studied. Cultures of both strains collected from any intervalof logarithmic growth phase exhibited high H2 photoproduction and nitrogenase activities when exposed tolimited time heat shock during the assay process. In contrast, the algal H2 photoproduction rate of bothstrains fluctuated with long term thermal stress caused hy increasing the growth temperature from 30℃ to36℃.The changes of nitrogenase (the key H2 photobiosynhetic enzyme) activities in the mutant PK84showed variation tendency similar to that of H2 photoproduction during exposure to thermal stress, indicat-ing that fluctuation of H2 photopnduction in the mutant was mainly due to the variation of nitrogenase ac-tivities. A temporary maximal H2 photoproduction in the mutant PK84 (wild type ATCC29413 ) was ob-served when cells po at 36℃ for 14 (6) days. However, the responses of nitrogenase activities in thewild type to thermal stress were not completely similar to those in the mutant in spite of similar variationsof H2 photoproduction in both strains. The data obtained in these studies suggested tha the activities ofother enzymes (in the wild strain) involved in H2 photoproduction were affected by thermal stress since H2photoporduction maximized or dropped to 0 without variation tendency similar to that of nitrogenase activi-ties.Furthermore, an enhancement of H2 photoproduction speed of the mutant strain cultured in a 4.4 Llaboratory photobioreactor was also observed when it was subjected to short time continuous charge of ar-gon, and temperature rise.All these results indicated that high temperature plays an important role in the photo-autotrophic H2photoproduction, and that long term thermal stress is unfavourable for net H2 phooproduction in bothstrains of A. variabilis though short-time heat shock is conducive to H2 photoproduction.

Studies on Phosphate Effect of Cytosine and Its Novel Photoproduct

Under the irradiation of a middle pressure mercury lamp(MPML), we found that the photo lyses of nucleobases, nucleosides and nucleotides were strongly enhanced by phosphates (termed phosphate effect). In order to explain this phenomenon, the photolytic systems of cytosine in phosphate solutions were selected and studied. Experimental results indicated that the UV irradiation (190-220 nm) in the emission spectra of MPML is responsible for the phosphate effect. Phosphates absorbing the UV (190-220 nm) energy are converted to phosphate radical anions, which react with cytosine, leading to a novel photoproduct with phosphate group (C 4H 6N 3O 5P). It has been isolated, purified and characterized by means of elementary analysis, UV, IR, EI MS, 1H NMR, 13 C NMR and 31 P NMR. The phosphate effect and its formation mechanism have been discussed.

Production of High-p_T Kaon and Pion in PP and Au-Au Collisions by Resolved Photoproduction Processes

Taking into account the effects of shadowing and jet quenching, the large transverse momentum distribution of K＋, π＋ and K＋/π＋ ratios at s = 200 GeV originating from resolved photoproduction processes is calculated based on perturbative quantum chromodynamics. It is found that the contribution of K＋ and π＋ produced by photoproduction processes is evident. The K＋ /π＋ ratios in Au-Au collisions show an obvious enhancement compared with p p collisions. The numerical results indicate that the photoproduetion processes are good modification for kaon and pion production.

J/ψ and T Photoproduction at LHC

Hard photoproduction of J/ψ and T at large hadron collider(LHC)Pb-Pb collisionswith CMS energy 6300 GeV/u is discussed in the process Pb+Pb→Pb+J/ψ+X with threetypes of equivalent photon spectrum functions.It turns out that the hard photoproductionprocesses can be used to probe several important problems such as the gluon distribution in thenucleus,gluon and heavy q.uark fragmentation of J/ψ,et al.In addition,the process alsoprovides a new way of testing the EMC effects.

Study on the Direct Photooxidation of Near-Infrared Absorbing Benzothiazolone Cyanine Dye

In this paper, direct photooxidation of benzothiazolone cyanine dye: in acetonitrile was studied. The photoproducts had been identified by (HNMR)-H-1 and fast atom bombardment (FAB) mass spectrometry. The results showed that the N-ethylbenzothiazolone (I), the ionic acid (II), and ionic aldehyde (III) are the principal photoproducts.

Analysis of data for γp → f1(1285)p photoproduction

The photoproduction of the f1(1285)meson off the proton target is investigated within an effective Lagrangian approach.The t-channelρ-andω-exchange diagrams,u-channel nucleon-exchange diagram,generalized contact term,and s-channel pole diagrams of the nucleon and a minimal number of nucleon resonances are taken into account in constructing the reaction amplitudes to describe the experimental data.Three different models,that is,the Feynman,Regge,and interpolated Regge models,are employed,where the t-channel reaction amplitudes are constructed in Feynman,Regge,and interpolated Regge types,respectively.The results show that neither the Feynman model with two nucleon resonances nor the interpolated Regge model with one nucleon resonance can satisfactorily reproduce the available data forγp→f1(1285)p.Nevertheless,in the Regge model,when any one of the N(1990)7/2^(+),N(2000)5/2^(+),N(2040)3/2^(+),N(2060)5/2^(-),N(2100)1/2^(+),N(2120)3/2^(-),N(2190)7/2^(-),N(2300)1/2^(+),and N(2570)5/2^(-)resonances is considered,the data can be well described.The resulting resonance parameters are consistent with those advocated in the Particle Data Group(PDG)review.Further analysis shows that,in the high-energy region,the peaks of γp→f1(1285)p differential cross sections at forward angles are dominated by the contributions from t-channelρ-andω-exchange diagrams,while in low-energy region,the s-channel pole diagrams of resonances also provide significant contributions to theγp→f1(1285)p cross sections.

First extraction of the proton mass radius and scattering length |αρ0p|from ρ^(0) photoproduction

As it involves the lightest physical states excited from the vacuum by the vector quark current,near-threshold ρ^(0)photoproduction is considered a possible way to research the proton radius and the absolute value of the scattering lengths of the ρ^(0)-proton interaction.In this study,under the assumption of a scalar form factor of dipole form,the value of the proton mass radius is calculated as(0.85±0.06) fm by fitting the differential cross section of the γp→ρ^(0)p reaction at near-threshold energy.For light vector meson photoproduction,because the exchange of a scalar quark-antiquark pair is not suppressed and should dominate the scalar gluon exchange,the radius we extract from ρ^(0)photoproduction is likely to represent the quark radius of the proton.This fact may explain why the value obtained in this study is very near the proton charge radius.Moreover,the absolute value of the ρ^(0)-proton scattering length |αρ^(0)p|=(0.31±0.06) fm is obtained for the first time within the vector meson dominance model.This result disobeys the rule that the absolute value of the vector meson and proton scattering length |αVp| increases with the meson’s mass,which can be attributed to treating the ρ^(0)meson as a point in the analysis.These results provide useful theoretical information for an in-depth understanding of proton structure and the proton-vector meson interaction.

Gluon gravitational form factors of protons from charmonium photoproduction

Inspired by the recent near-threshold J/ψphotoproduction measurements,we discuss gluon gravitational form factors(GFFs)and internal properties of the proton.This work presents a complete analysis of the proton gluon GFFs connecting the gluon part of the energy-momentum tensor and the heavy quarkonium photoproduction.In particular,a global fitting of the J/ψdifferential and total cross section experimental data is used to determine the gluon GFFs as functions of the squared momentum transfer t.Combined with the quark contributions to the D-term form factor extracted from the deeply virtual Compton scattering experiment,the total D-term is obtained to investigate their applications in describing the proton mechanical properties.These studies provide a unique perspective on investigating the proton gluon GFFs and important information for enhancing QCD constraints on the gluon GFFs.

Photo-production of lowest∑^(*)_(1/2) state within the Regge-effective Lagrangian approach

Because the lowest ∑^(*) state with quantum numbers spin-parity J^(P)=1/2-is far from being established experimentally and theoretically,we perform a theoreticalstudy on the ∑^(*)_(1/2)-photo-production within the Regge-effective Lagrangian approach.Considering that ∑^(*)_(1/2)-couples to the KN channel,westudy the contributions from the t-channel K^(*) exchange diagram.Moreover,the contributions from the t-channel K^(*) exchange,s-channel nucleon pole,u-channel 2 exchange,and contact term are considered.The differential and total cross sections of the processγn→K+∑^(*)_(1/2)-are predicted with our model parameters.The results should help in experimentaly searching for the ∑^(*)_(1/2)-state in the future.

Photolysis of chlortetracycline in aqueous solution:Kinetics,toxicity and products

The aqueous photodegradation of the widely used antibiotic chlortetracycline（CTC） was investigated under simulated sunlight.The quantum yield of photodegradation increased from 3.3 × 10-4 to 8.5 × 10-3 within the pH range of 6.0 to 9.0.The presence of Ca2＋,Fe3＋,and NO3-enhanced the photodegradation of CTC,whereas Mg2＋,Mn2＋,and Zn2＋ inhibited the degradation with the order Mn2＋ Zn2＋ Mg2＋ at pH 7.3.The monovalent cations（Na＋ and K＋） had negligible effect on the photolysis of CTC.Fulvic acid（FA） decreased the photodegradation of CTC due to light screening effect.Hydrogen peroxide（H2O2） was formed concurrently with direct photodegradation of CTC.The generation rate of H2O2 increased from 0.027 to 0.086 μmol/（L.min） when the pH ranged from 6.0 to 9.0.The CTC solution was about three-fold more toxic to the Photobacterium phosphoreum bacteria after irradiation,suggesting that the photoproducts and H2O2 formed in the CTC solution exhibited high risk on the bacteria.By LC-ESI（＋）-MS,the photoproducts of CTC were identified.The direct photodegradation of CTC was involved in hydroxylation and N-demethyl/dedismethyl processes.The main photoproducts included the iso-CTC analog containing hydroxyl groups（m/z 511.4 and 495.4）,and the N-demethyl/dedismethyl products of the photoproduct m/z 495.4（m/z 481.3 and 467.4）.In addition,the photochemical dechlorination of CTC led to tetracycline（m/z 445.5）.

Loss of algal Proton Gradient Regulation 5 increases reactive oxygen species scavenging and H2 evolution

Summary We have identified hpm91, a Chlamydomonas mutant lacking Proton Gradient Regulation5 （PGRS） capable of producing hydrogen （H2） for 25 days with more than 3o-fold yield increase compared to wild type. Thus, hpm91 displays a higher capacity of H2 production than a previously characterized pgr5 mutant. Physiological and biochemical characterization of hpm91 reveal that the prolonged H2 production is due to enhanced stability of PSII, which correlates with increased reactive oxygen species （ROS） scavenging capacity during sulfur depriva- tion. This anti-ROS response appears to protect the photosynthetic electron transport chain from photo- oxidative damage and thereby ensures electron supply to the hydrogenase.

Energy calibration of tagged photons by the d(γ,π^-pp) reaction

The energy of tagged photons, which were provided from the internal photon tagging system of the Laboratory of Nuclear Science, Tohoku University, has been calibrated using the d（γ,π-pp） reaction. Charged pions and protons in the final state were detected with the Neutral Kaon Spectrometer （NKS2）. Photon energies were obtained from the reaction of d（γ,π-pp）. The derived photon energy was consistent with the design of the tagger system and the previous measurement using electron-positron pair production. The consistency demonstrates the performance of NKS2 and the capability of the photon energy calibration using d（γ,π-pp）.

Photoproduction of mesons off the deuteron:quasifree and coherent processes

Photoproduction of mesons off the deuteron has been investigated at a tagged photon beam of the Bonn ELSA accelerator with the combined Crystal Barrel - TAPS electromagnetic calorimeter for incident photon energies up to 2.5 GeV. The mesons have been detected in coincidence with recoil protons, neutrons and deuterons. This allow the measurement of meson production reactions off the quasifree nucleons bound in the deutron, as well as the coherent production off the deuteron. The comparison of quasifree proton reactions to free proton reactions can confirm or invalidate possible nuclear effects on the extracted cross section reactions. Furthermore the isospin composition of a resonance can be estimated from the comparison of quasifree proton and neutron reactions. The quasifree photoproduction of the η＇ and π°η mesons off nucleons and the coherent photoproduction of π°η--pairs off the deuteron are discussed.