Photooxidation stability of phytosterols with different relative spatial positions in different particles

The aim of this study was to investigate the effects of relative spatial position of stigmasterol on its photooxidation stability in different particles.Phytosterol oxidation products(POPs)from phytosterol oxidation were successfully isolated and studied using solid phase extraction(SPE)technology in conjunction with GC-MS.The photooxidation stability of stigmasterol in four particles was as follows:zein stabilized particles(ZPs)≈zein-pectin stabilized particles(ZPPs)>soy protein isolate(SPI)-pectin stabilized particles(SPPs)>SPI stabilized particles(SPs).7β-Hydroxy and 5β,6β-epoxy was the main POPs in the first and second oxidation stages,respectively,which reached 8,945±43μg/g and 6,010±289μg/g after 240 min UV light exposure treatment in SPs.When stigmasterol was hydrophobically adsorbed on the surface of SPs,the network gel generated by pectin outside SPPs prevented photooxidation of stigmasterol.When stigmasterol was encapsulated in the interior of ZPs,the blocking effect of pectin in ZPPs became insignificant.The study provided a feasible development direction for the storage and quality control of phytosterols as dietary supplements.

Physiological Basis of Photosynthetic Tolerance to Photooxidation and Shading in Rice

Thirty genotypes from rice germplasm were identified under photooxidation and shading condition and divided into four basic types : (1) cultivars tolerant to both photooxidation and shading, (2) cultivars tolerant to photooxidation but sensitive to shading, (3) cultivars tolerant to shading but sensitive to photooxidation, and (4) cultivars sensitive to photooxidation and shading. A comparative study of photosynthetic characteristics of a cultivar (cv. Wuyujing 3) that is tolerant and a cultivar (cv. Xiangxian) that is sensitive to both photoinhibition and shading showed that the photochemical efficiency of PSⅡ ( F v/F m ) and the content of PSⅡ_D1 protein in the tolerant cultivar “Wuyujing 3” decreased less under photoinhibition conditions as compared with “Xiangxian”. Under photooxidation conditions, superoxide dismutase was induced rapidly to a higher level and the active oxygen O - built up to a lower level in “Wuyujing 3” than in “Xiangxian”. At the same time, the photosynthetic rate decreased by 23% in “Wuyujing 3” vs. 64% in “Xiangxian”. Shading (20% natural light) during the booting stage caused only small decreases (7%-13%) in RuBisCO activity and the photosynthetic rate in “Wuyujing 3” but showed marked decreases (57%-64%) in “Xiangxian” which corresponded to the decreases in grain yield in the two cultivars (38% and 73%, respectively). The correlation analysis showed that the tolerance to photooxidation is mainly related to PSⅡ_D1 and that to shading is mainly related to RuBisCO activity. This study provided a simple and effective screening method and physiological basis for crop breeding in enhancing tolerance to both high and low radiation.

Characteristics of Chlorophyll Fluorescence and Membrane-lipid Peroxidation of Various High-yield Rices Under Photooxidation Conditions

Using various high-yield rices (Oryza sativa L.) such as japonica cultivar 9516, two parental line hybrid rice between subspecies with more japonica element Peiai 64/E32, Liangyoupeijiu (Peiai 64/9311), and indica hybrid rices X07S/Zihui 100, Gangyou 881, Shanyou 63 as the materials, the characteristics of chlorophyll fluorescence and membrane-lipid peroxidation of detached leaves at booting stage under photooxidation conditions were studied. In comparison with indica hybrid rice, after the photooxidation treatment, the primary photochemical efficiency of PS II (F-v/F-m), quantum yield of linear electron transport of PS II (Phi(PSII)) and photochemical quenching coefficient (qP) in japonica cultivar and hybrid rice with japonica decreased less. This indicated that high-yield rice with japonica was able to maintain higher capability of light energy conversion, resulting in the alleviation of photoinhibition. Meanwhile, the higher activities of protective enzymes such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) led to the less accumulation of endogenous active oxygen (O-(2)(radical anion), H2O2) and less content of the malondialdehyde (MDA) and the less decline of chlorophyll and protein contents, indicating a stronger tolerance to photooxidation. The changes in contents of chlorophyll and protein among various nee cultivars during photooxidation treatment were consistent with the decline of chlorophyll content from heading stage to maturation stage under natural conditions. Statistical analysis showed that there was a significant correlation between the indexes of tolerance to photooxidation and the rate of seed setting, implying that the cultivar tolerated to photooxidation had higher resistance to early aging of leaf. These results suggested that from a view of superhigh-yield breeding, considering both the utilization of heterosis and the resistance to early aging of leaf, introduction of japonica element tolerating to photooxidation into the rice sterile line (maternal plant) is a breeding strategy worthy to pay great attention to.

Photooxidation in Leaves of Facultative CAM Plant Sedum spectabile at C_3 and CAM Mode

The switch from C-3 to CAM pathway was induced by water stress in a C-3/CAM intermediate plant Sedum spectabile Boreau. Typical CAM criteria were observed upon 15 d of withholding water. Leaf delta(13)C value (-%) and water content showed a linear correlation fashion. Chlorophyll fluorescence parameters and antioxidative capacity were altered by water stress. Phi(PSII) and q(P) were reduced by 50% and 34% of the control, respectively, while NPQ rose ca. 180%. SOD activity and ability to scavenge DPPH. free radical went down but membrane permeability changed slightly. However, when an additional photooxidation by MV with high PPFD was carried out with leaf discs from watered (C-3 mode) and drought plants (CAM mode), q(P) and Phi(PSII) in leaves at induced CAM mode stage continuously decreased to a very low level. High 1 - q(P) value (0.86) and 1 - q(P)/NPQ ratio (>1) indicated the presence of high reduction state and unbalance of light energy budget. Together with the marked loss of membrane integral, it was evidenced that photooxidative damage was more serious in the induced CAM mode than in the C-3 mode. No advantage of photooxidation tolerance was found at the induced CAM expression stage of the facultative CAM plant, as compared with its C-3 mode stage, and also with the constitutive CAM plants reported previously. The differences in photooxidation sensitivity between the inducible CAM expressing plant and the constitutive CAM plant were discussed.

Effects of seed aerosols on the growth of secondary organic aerosols from the photooxidation of toluene

Hydroxyl radical （.OH）-initiated photooxidation reaction of toluene was carried out in a self-made smog chamber. Four individual seed aerosols such as ammonium sulfate, ammonium nitrate, sodium silicate and calcium chloride, were introduced into the chamber to assess their influence on the growth of secondary organic aerosols （SOA）. It was found that the low concentration of seed aerosols might lead to high concentration of SOA particles. Seed aerosols would promote rates of SOA formation at the start of the reaction and inhibit its formation rate with prolonging the reaction time. In the case of ca. 9000 pt/cm^3 seed aerosol load, the addition of sodium silicate induced a same effect on the SOA formation as ammonium nitrate. The influence of the four individual seed aerosols on the generation of SOA decreased in the order of calcium chloride〉sodium silicate and ammonium nitrate〉ammonium sulfate.

The Relationship Among Photoinhibition, Photooxidation and Early Aging at a Late Development Stage in Different Varieties with High Yield

Using six high yield varieties from different ecological districts in China the parameters of Chl fluorescence, the performance of membrane lipid peroxidation and the reduction of Chl content in flag leaf under natural condition at the later developmental stages (from heading stage to mature stage). The results showed that Fv/Fm , decreased gradually, the excessive light energy led to the accumulation of active oxygen O2-, H2O2 and the product of membrane-lipid peroxidation, MDA, which resulted in the reduction of Chl content and early aging due to photooxidation during the course of senescence of flag leaf. This phenomenon varied obviously in rice varieties. When comparina japonica tolerant to photooxidation, Fv/Fm in indica shanyou 63 susceptible to photoxidation decreased significantly. An increase of active oxygen and a sharp drop of Chl content, resulted in 'yellowish' early aging and influenced filling and setting of rice grain. The mechanism on early aging in indica was related to light and temperature conditions in filling stages. On a fine day (above 251), PS Ⅱ reaction center exhibited a dynamic change on revisable inactivation. Under strong midday light, PS Ⅱ function in indica exhibited obvious down-regulation and photoinhibition; Under strong light with low temperature, PS Ⅱ resulted in photodamage, showing early aging, which were related to the degradation of PSⅡ - D1 Protein and the inhibition of the endogenous protecting system such as Xanthophyll cycle and the enzymes of scavenging active oxygen. The results suggested that for a view of high-yield breeding, on the basis of a good type-plant, giving consideration to the utilization of heterosis and resistance to early aging, selecting japonica or a sterile line with japonice genotype as maternal was a breeding strategy worthy of being paid more attention.

Photooxidation of hydrochlorofluocarbons and hydrofluorocarbons initiated by OH radicals

Under simulated atmospheric condition, photoomdation for HCFC-22 + H2O2, HCFC-22 + H2O2+O2, HFC-134A + H2O2 and HFC-134A + H2O2+ O2 systems were studied.H2O2 was irradiated by low pressure mercury lamp and produced OH radicals. The OH radicals can initiate photooxidation of HCFC-22 and 134A. The products of photooxidation were determined by a Fourier Transform infrared Spectroscopy with a 20ml long path cell. The products were COF2,CO2, HCI, H2O and HF for HCFC-22 + H2O2 system, HO, CO2, HCI and HF for HCFC-22 +H2O2 +O2 system, HCOF, CF3OOCF3,CO2, H2O and HF for HFC-134A +H2O2 system, HCOF, CO2, H2O, and HF for HFC-134A + H2O2+ O2 system. Based on those results, the mechanisms of photooxidation were suggested.

Characterization of products from photooxidation of toluene

Photooxidation reaction of toluene in smog chamber systems was initiated by the UV radiation of tolucne/CH5ONO/NOx mixtures. The products of the photooxidation reaction of toluene and its subsequent reactions were analyzed directly utilizing Fourier transform infrared spectrometer （FTIR）. Detailed assignments to FTIR spectrum of gas-phase products were given. The information of some important functional groups in the products, such as, carbonyl groups （C-O）, hydroxyl groups （-OH）, carboxylic acid （- COOH）, C-C bonding, N O bonding and C-H bonding （C H）, was got from this analysis. These results were compared to those analyzed by aerosol time of flight mass spectrometer （ATOFMS）. It was found that there are some differcnccs between FTIR analysis of gas-phase products and that of particle-phase, for example, the products with carbonyl groups, which were connected to unsaturated chemical bonds, was relatively higher in the gas phase, while kctoncs, aldehydes, carboxylic acid and organonitrates were the dominant functional groups in the aerosol-phase reaction products. The possible reaction pathways of some important products in the gas phase were also discussed.

Photooxidation of Furfural with Phthalocyanine-sensitized TiO_2 Particle Under Xenon Lamp

Copper phthalocyanine was selected as the photosensitizer to sensitize TiO2 in this experiment with furfural as the target pollutant. The composite catalysts（TiO2/CuPC） obtained showed a great activity under a xenon lamp. By experiments, the optimal preparation conditions of the composite catalysts were set as follows ： the CuPC loading mass fraction was 1.5%, the mass fraction of acetylacetone was 0. 3% , and the stirring time was 10 h. UV-Vis diffuse reflectance spectra, XRD, and BET were used to characterize the properties of the composite catalysts, which showed that after loading CuPC on TiO2, the composite catalyst retained the same crystal structure as pure TiO2 and the wavelength range of its absorption spectrum was broadened to 600-700 nm while its surface area was smaller than that of the pure TiO2. Under the optimal conditions, 20 mg/L furfural solution was degraded by nearly 90% and TOC by about 70%. When the catalyst was reused 6 times, the activity of the catalyst was still retained by about 75%.

The Effects of Accelerated Photooxidation on Molecular Weight and Thermal and Mechanical Properties of PHBV/Cloisite 30B Bionanocomposites

The effects of accelerated photooxidation on the molecular weight and thermal and mechanical properties of Cast PHBV and PHBV/Cloisite 30B(3 wt%)bionanocomposites are investigated herein.Through size exclusion chromatography(SEC)analysis,a significant decrease in both weight and number average molecular weights was observed for all irradiated samples over time,resulting from the chain scission mechanism.Differential scanning calorimetry(DSC)data indicated a decrease in degree of crystallinity and melting temperature after UV exposure,with the appearance of double melting peaks related to the changes in the crystal structure of PHBV.Thermal stability,tensile and thermo-mechanical properties were also reduced consecutively in photooxidation,being more pronounced for Cast PHBV.This study shows that the incorporation of Cloisite 30B in PHBV provides a better resistance to photooxidation in comparison with the neat polymer.

Kinetic Characteristic of Photooxidation of Cypermethrin by Organic Peroxy Radical

The kinetic characteristic of photolysis of cypermethrin (CPM) sensitized by acetophenone (AP) and the effect of probe substance 2,6-Di-tert-butyl-4-methylphenol and tetralin is studied in this report. It showed that the photolysis rate of CPM increases slightly with the increase of AP concentration; photolysis rate of CPM has no relationship with [CPM] itself; The more dipolar moment the solvent has, the more the interaction between radical and solvent has, and the slower the photolysis of CPM is. The addition of radical probe substance confirms that ROO·is more than RO·. The steady-state concentration of ROO·is about 10?8 mol·L?1.

EFFECT OF PHOTOOXIDATION ON PHOTOLUMINESCENCE OF N, N'-DIPHENYL-N, N'-DI(M-TOLYL)-BENZIDINE AND RUBRENE CODOPED PMMA THIN FILMS

In this paper, the PMMA films doped with N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine and rubrene were fabricated by spin coating, and the effect of photooxidation on the photoluminescence of the doped PMMA thin films was investigated. The results showed that under the irradiation of 350nm UV light, N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine can sensitized rubrene and results in the enhancement in the photooxidation of rubrene. The effect of photooxidation on the photoluminescence from rubrene was more obvious. Both lifetime measurement and in situ measurement of photoluminescence showed that rubrene molecules exist in two chemical surroundings.

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.

Effects of NO_(2) and SO_(2) on the secondary organic aerosol formation fromβ-pinene photooxidation

Elucidating the effects of anthropogenic pollutants on the photooxidation of biogenic volatile organic compounds is crucial to understanding the fundamental mechanisms of secondary organic aerosol(SOA)formation.Here,the impacts of NO_(2)and SO_(2)on SOA formation from the photooxidation of a representative monoterpene,β-pinene,were investigated by a number of laboratory studies.The results indicated NO_(2)enhanced the SOA mass concentrations and particle number concentrations under both low and highβ-pinene conditions.This could be rationalized that the increased O_(3)concentrations upon the NO_(x)photolysis was helpful for the generation of more amounts of O_(3)-oxidized products,which accelerated the SOA nucleation and growth.Combing with NO_(2),the promotion of the SOA yield by SO_(2)was mainly reflected in the increase of mass concentration,which might be due to the elimination of the newly formed particles by the initially formed particles.The observed low oxidation degree of SOA might be attributed to the fast growth of SOA,resulting in the uptake of less oxygenated gas-phase species onto the particle phase.The present findings have important implications for SOA formation affected by anthropogenic–biogenic interactions in the ambient atmosphere.

“Steric Armor”Strategy of Blue Fluorescent Emitters against Photooxidation-Induced Degradation

Stability against oxygen is an important factor affecting the performance of organic semiconductor devices.Improving photooxidation stability can prolong the service life of the device and maintain the mechanical and photoelectric properties of the device.Generally,various encapsulation methods from molecular structure to macroscopic device level are used to improve photooxidation stability.Here,we adopted a crystallization strategy to allow 14H-spiro[dibenzo[c,h]acridine-7,9′-fluorene](SFDBA)to pack tightly to resist fluorescence decay caused by oxidation.In this case,the inert group of SFDBA acts as a“steric armor”,protecting the photosensitive group from being attacked by oxygen.Therefore,compared with the fluorescence quenching of SFDBA powder under 2 h of sunlight,SFDBA crystal can maintain its fluorescence emission for more than 8 h under the same conditions.Furthermore,the photoluminescence quantum yields(PLQYs)of the crystalline film is 327%higher than that of the amorphous film.It shows that the crystallization strategy is an effective method to resist oxidation.

Broadband Visible Light Harvesting BODIPY-Perylene Dyad and Triad:Synthesis,Photophysical Properties,and Photooxidation Applications

In this study,diodo boron dipyrromethene(BODIPY)is employed a8 the energy donor and 3,4,9,10-perylene tetracarboxylic dianhydride(PDA)as the energy acceptor,enabling the synthesis of two new compounds:a BODIPY-perylene dyad named P1,and a triad named P2.To investigate the impact of the energy donor on the photophysical processes of the system,P1 comprises one diodo-BODIPY unit and one PDA unit,whereas P2 contains two diodo-BODIPY moieties and one PDA unit.Due to the good spectral complementarity between diiodo-BODIPY and PDA,these two compounds exhibit excellent light-harvesting capabilities in the 400-620 nm range.Steady-state fluorescence spectra demonstrate that when preferentially exciting the diodo-BODIPY moiety,it can effectively transfer energy to PDA;when selectively exciting the PDA moiety,quenching of PDA fluorescence is observed in both P1 and P2.Nanosecond transient absorption results show that both compounds can efficiently generate triplet excited states,which are located on the PDA part.The lifetimes of the triplet states for these two compounds are 103 and 89μs,respectively,significantly longer than that of diiodo-BODIPY.The results from the photooxidation experiments reveal that both P1 and P2 demonstrate good photostability and photooxidation capabilities,with P2 showing superior photooxidative efficiency.The photooxidation rate constant for P2 is 1.3 times that of P1,and its singlet oxygen quantum yield is 1.6 times that of P1.The results obtained here offer valuable insights for designing new photosensitizers.

Interface boosted highly efficient selective photooxidation in Bi_(3)O_(4)Br/ Bi_(2)O_(3) heterojunctions

Selective photooxidation of amines to biologically important imines is in great demand for industrial applications.The conversion efficiency and selectivity of the process are strongly dependent on the activation of photocatalytic molecular oxygen(O_(2))into reactive oxygen species.Here,we propose the construction of rich interfaces to boost photocatalytic O_(2) activation by facilitating the transfer of photocarriers.Taking Bi_(3)O_(4)Br/Bi_(2)O_(3) heterojunctions as an example,rich interfaces facilitate electron transfer to adsorbed O_(2) for superoxide(O_(2)⋅^(-))generation,thus achieving≥98%conversion efficiency and selectivity for benzylamine and benzylamine derivatives.This study offers a valid method to design advanced photocatalysts for selective oxidation reactions.

The anti-photooxidation of anthocyanins-rich leaves of a purple rice cultivar

In the leaf of rice (Oryza sativa L.) cultivar Yunnan purple rice,the anthocyanins with an obvious absorption peak at 530nm were distributed in the cells of upper and lower epidermis,bulliform tissue and bristle. The maximal photosynthetic oxygen evolution rate and chlorophyll content in flag leaves were 28% and 23%,respectively,more than the common green leaf rice cultivar Chijiaoru-anzhan. Higher chlorophyll content is probably one of the physiological adaptations for enhancing light harvesting capacity of the antenna in photosystems in this cyanic leaves species. Upon the photooxidation of leaf segments mediated by methyl viologen in weak light for 3 days,the distinct bleaching of anthocyanins in purple rice was associated with the reduction of scavenging ability to DPPH· free radical ability and the increase in membrane leakage rate. But almost no changes in contents of flavonoids and total phenolics were observed. Chlorophyll fluorescence parameters Fv/Fo,qP and φPSⅡ decreased with the increase in NPQ and DES of xanthophylls cycle after photooxidation treatment. Green rice leaves showed more decrease in DPPH· scavenging rate and more increase in cell membrane leakage rate but showed a trace of anthocyanins during photooxidation. It is sug-gested that anthocyanin may be a beneficial and primary antioxidant in sun cyanic rice leaves against oxidative stress induced by environmental adversity. And photooxidation could induce different changing patterns of anthocyanins between the tested purple and green rice leaves.

Real-time detection of individual secondary organic aerosol particle from photooxidation of toluene using aerosol time of flight mass spectrometer

Photooxidation of the aromatic hydrocarbon toluene and its subsequent reactions were carried out using UV-irradiation of toluene/CH_(3)ONO/NO/air mixtures in a home-made smog chamber.The secondary organic aerosols could be formed after those oxidation products of semi-volatile or-ganic compounds were partitioned between gas phase and particle phase.The aerosol time of flight mass spectrometer(ATOFMS)was used to measure size and molecular composition of individual secondary organic aerosol particle.Size distribution and chemical composition of secondary organic aerosol were got in real time.

SDS-PAGE study on photooxidation damage of lysozyme induced by riboflavin

The photooxidation damage of lysozyme under 315-375 nm irradiation in the presence of riboflavin was studied by using sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE).Indica- tions showed that the mechanisms and products of oxidative damage were relative to the concentra- tion of riboflavin,the time of irradiation and the ambience.The type I process was examined in a nitrogen saturated solution,whereas both type I and type II were observed in an aerobic atmosphere and type II was the dominant process.The study also suggested that antioxidants,such as melatonin, can reduce the damage of lysozyme effectively.