EPR study of charge separation associated states and reversibility of surface bound superoxide radicals in SrTiO_(3) photocatalyst

Understanding the processes of charge generation, transfer and capture is important for the design and synthesis of efficient photocatalysts. In this work, light-induced charge separation and effect of O_(2) on electron transfer processes in SrTiO_(3) were investigated by electron paramagnetic resonance(EPR). It was found that photoinduced electron transfer from O_(2)- to Ti^(4+) produced Ti^(3+) and O- redox radical pairs under vacuum condition. Under oxygen atmosphere, however, surface bound superoxide radicals O_(2)-were formed by electron reduction of adsorbed oxygen at initial photoirradiation stage, and quenched by the reverse electron transfer to Ti^(4+) upon further photoirradiation. Formation of long-lived charge separation associated [Ti^(3+)---O-] species and the reversibility of surface bound superoxide radicals mediating the processes of photogenerated electrons may be accountable for the high activity of SrTiO_(3) in photocatalytic water splitting reaction.

Photocatalytic degradation kinetics and mechanism of pentachlorophenol based on superoxide radicals

The micron grade multi-metal oxide bismuth silicate （Bi 12 SiO 20,BSO） was prepared by the chemical solution decomposition technique.Photocatalytic degradation of pentachlorophenol （PCP） was investigated in the presence of BSO under xenon lamp irradiation.The reaction kinetics followed pseudo first-order and the degradation ratio achieved 99.1% after 120 min at an initial PCP concentration of 2.0 mg/L.The pH decreased from 6.2 to 4.6 and the dechlorination ratio was 68.4% after 120 min at an initial PCP concentration of 8.0 mg/L.The results of electron spin resonance showed that superoxide radical （O 2 · ） was largely responsible for the photocatalytic degradation of PCP.Interestingly,this result was different from that of previous photocatalytic reactions where valence band holes or hydroxyl radicals played the role of major oxidants.Some aromatic compounds and aliphatic carboxylic acids were determined by GC/MS as the reaction intermediates,which indicated that O 2 · can attack the bond between the carbon and chlorine atoms to form less chlorinated aromatic compounds.The aromatic compounds were further oxidized by O 2 · to generate aliphatic carboxylic acids which can be finally mineralized to CO 2 and H 2 O.

Effects of Superoxide Radical on Root System Growth and Auxin Distribution in Rice

[Objective] This study aimed to investigate the effect of superoxide radical on root system growth and auxin distribution in rice （Oryza sativa L. cv Zhonghua No.11）. [Method] With rice Zhonghua No.ll as the experimental material, the effects of DDC （SOD inhibitor） and Tiron （superoxide radical scavenger） on the root system growth, superoxide radical generation and root system auxin distribution in rice were analyzed. [Result] The growth and elongation of primary and adventitious roots were significantly promoted by DDC, while Tiron significantly inhibited the growth and elongation of shoots, primary roots and their lateral roots, and also suppressed the formation and growth of the adventitious roots as well as the elongation of their lateral roots. The superoxide radical was increased with the induction of DDC, while Tiron decreased the accumulation of superoxide radical. Increased accumulation of auxin in the vascular bundle and behind the elongation zone was observed in DDC- treated roots, while the treatment with Tiron resulted in a decrease of auxin in the same position. [Conclusion] This study indicated that the regulation of rice root sys- tem growth by superoxide radical was closely related with the accumulation and distribution of auxin.

Effect of Cu(11)-Salicylate in Micellar Systems onScavenging Superoxide Ion Released by CulturedMacrophages

基于胶束与球状蛋白的相似性，用胶束模拟超氧化物歧化酶（ＳＯＤ）的微环境，以促进ＳＯＤ模拟物─水杨酸铜络合物对Ｏ歧化的催化作用，达到清除Ｏ＿２的目的。本文首次用培养的巨噬细胞受刺激产生的“呼吸暴发”为Ｏ的发生源，研究了在ＣＴＡＢ、ＳＤＳ、ＴｒｉｔｏｎＸ－１００及Ｔｗｅｅｎ２０胶束体系中水杨酸铜络合物对Ｏ的清除作用。研究结果表明，以水杨酸铜－ＳＤＳ胶束体系对Ｏ的清除率最高，达９０．４％。其他胶束体系对Ｏ的歧化亦均有促进作用。

New Active Organic Substance in Oyster Shell Capable of Scavenging Oxygen Free Radicals with High Efficiency

A light purple organic active substance capable of scavenging hydroxyl radical（OH） with a high efficiency was extracted from Oyster shell at an extraction rate of 2.49%. It was found for the first time that this active substance may scavenge OH with the efficiency far higher than that of vitamin C. This active substance may scavenge also superoxide radical（O2） although the scavenging efficiency is far lower than that of vitamin C. Infrared spectrometry and routine chemical analysis primarily reveal that this active substance belongs to glycoprotein.

Superoxide Anion Radical Scavenging Ability of Quaternary Ammonium Salt of Chitosan

A series of N-alkyl or N-aryl chitosan quaternary ammonium salt were prepared using 96% deacetylated chitosan. Their scavenging activities against superoxide anion radical were investigated by chemiluminescence. The IC50 values of these compounds range from 280 to 880 μg/mL, which should be attributed to their different substitutes.

Formation of Superoxide Radical and Hydrogen Peroxide Enhanced by Trinitrotoluene in Rat Liver, Brain, Kidney, and Testicle in Vitro and Monkey Liver in Vivo

Trinitrotoluene (TNT) increased the formation of adrenochrome from adrenaline and the formation of formaldehyde from methanol in rat liver mitochondria and microsomes in vitro as well as in monkey liver mitrochondria and microsomes in vivo. The effects were more prominent at higher TNT concentrations. These findings indicate that TNT enhances the production of superoxide radicals (O_2^-) and hydrogen peroxide (H_2O_2). The production of O_2^- was more prominent in systems containing added TNT than in those containing added benzyl viologen. H_2O_2 production by mitochondria was more pronounced in the liver than in other organs, but its production by microsomes was more pronounced in the brain than in other organs. The results suggest that TNT undergoes cycling reduction which produces oxidative stress. 1989 Academic Press, Inc.

Study on Inhibition Effects of Rare Earths on Superoxide Anion Radical by Using Pulse Radiolysis

The inhibition effect of rare earths on the production of ·O - 2 produced by radiolysis of aqueous sodium formate saturated with O 2 with high energy pulse electron beam was studied. The result indicates that rare earth nitrate obviously inhibits the production of ·O - 2 . The inhibition rate is between 28 6% and 92%. The inhibition effect increases with the increase of rare earth nitrates concentration. The distinguish dose effect relationship was observed.

Mechanism of Cerium Ions Scavenging Superoxide Radical

The mechanism of cerium ions scavenging superoxide radical(O÷2) has been studied. The results show that (1) Ce^3+ can reduce O÷2 to H_2O_2 while it is oxidized to Ce^4+; (2) Ce^4+ can oxidize O÷2 to O_2 while it is reduced to Ce^3+.

Preparation of (±)-5,6,7-Trioxygenated Dihydroflavonols and Evaluation of their Superoxide Radical Scavenging Activity

The synthesis of （±）-5, 6, 7-trioxygenated dihydroflavonols was carried out. All synthetic compounds were passed through superoxide radical scavenging activity in vitro. Compounds 1 e and 1 g exhibited significant bioactivity with the inhibitory rates of 68.1% and 80.9% at 40 μg/mL, respectively.

Regulation of Superoxide Anion Radical During the Oxygen Delignification Process

In this study, the superoxide anion radicals were generated by the auto-oxidation of 1,2,3-trihydroxybenzene and determined by UV spectrophotometry, and the reaction was found to be facilitated by anthraquinone-2-sulfonic acid sodium salt. The bamboo kraft pulps were treated by the 1,2,3-trihydroxybenzene auto-oxidation method or the 1,2,3-trihydroxybenzene auto-oxidation combined with anthraquinone-2-sulfonic acid sodium salt to show the ef-fect of the superoxide anion radicals during the oxygen delignification of bamboo kraft pulp and the enhancing af-fect of anthraquinone compounds as an additive on delignification. The results indicated that the superoxide anion radicals could react with lignin and remove it from pulp with negligible damage on cellulose, and the an-thraquinone-2-sulfonic acid sodium salt could facilitate the generation of superoxide anion radical to enhance delig-nification of pulps. The oxygen delignification selectivity could be improved using the 1,2,3-trihydroxybenzene auto-oxidation system combined with anthraquinone-2-sulfonic acid sodium salt.

A New Method of Superoxide Free Radical Determination in Ischemia and Reperfusion Injury of Rat Liver

The present study was designed to utilize the chemiluminescence(CL)method for O2- analysis in ischemia and reperfusion of the whole rat liver. The results indicated that the O2- level was lower after 30 and 60 min ischemia. After 40 min reperfusion, the level of O2- increased obviously,reaching about 8. 3-fold (30min ischemia) and 9. 0-fold (60 min ischemia) (P<0.001,P<0.01) respectively.The results also show that Chinese Traditional Medicines ligustrazine and salvia compound can scavenge O2- effectively.

Hyperlipidemia and erectile dysfunction

We have done consecutive studies to investigate the effects of impaired lipid metabolism on the contractile and re-laxation response of cavernous smooth muscles and to elucidate its pathogenesis: 1) incidence of hyperlipidemia in im-potent patients; 2) erection response to intracavemous injection of papaverine in impotent patients with hyperlipidemia;3) relaxation responses of isolated cavemosal smooth muscles to endothelium-independent and endothelium-dependentvasodilators in impotent patients with hypercholesterolemia or hypertriglyceridemia; 4) involvement of superoxide radi-cal in the impaired endothelium-dependent relaxation of cavemous smooth muscle in hypercholesterolemic rabbits; S)effects of isolated lipoproteins and triglyceride, combined oxidized LDL plus triglyceride, and combined oxidized LDLplus HDL on contractile and relaxation response of rabbit cavemous smooth muscles; 6) involvement of e-NOS in theimpaired endothelium-dependent relaxation of cavemous smooth muscle in hypercholesterolemic rabbit. Hypercholes-terolemia may cause impairment of endothelium-dependent relaxation. Oxidized LDL is the major causative cholesterolof the impaired relaxation response. A chain reaction, the production of superoxide radicals and functional impairmentof eNOS may be a major cause of the functional impairment in the early stages of hypercholesterolemia.

SOD-like Activities of Fifteen Constituents from Rhubarb

It is important to search for the ingredients with SOD—like activity present in Chinese traditional drugs.Four classes of constituents including fifteen compounds isolated from Chinese rhubarb were studied for their SOD-like activity by determining the percentage of scavenging effect of the superoxide radical anion (O2),(S％),The results showed that the SOD-like activities of four tanninoid compounds were stronger among which(—)-epi- catechin has the strongest SOD-like activity at lower concentrations:the activity of five stil- bene compounds is weaker:while chrysophanol-8-glucoside and desoxyrhaponticin have no SOD-like activity and,on the contrary.may promote the production of O_2^-

Role of the reduction site in the fluorinated or sulfated TiO_2 photocatalytic process

In this article, the effects of ZiO2 surface fluorination and sulfation, on the active oxygen species formed at the reduction site in the photocatalytic process, namely O2^＊- and H2O2, were investigated from a new perspective. The superoxide radical, （O2^＊-）, was determined by colorimetry of nitroblue tetrazolium, a prominent O2^＊- scavenger. Hydrogen peroxide （H2O2） was estimated by using the iodide-starch method. In the naked TiO2 photocatalysis, O2^＊-, though less reactive, was a very important intermediate. When the TiO2 surface was fluorinated, more O2^＊- and H2O2 were produced, which indicated that the surface modification could greatly reduce the recombination of photogenerated electrons and holes, thus enhancing the photocatalytic rate. In the sulfated system, photocatalysis proceeded with a more complicated mechanism. These results added support to the view of fluoride-induced enhancement and sulfide＇s nonappreciable inhibition effect.

Synthesis, characterization, and biological activities of Pt(Ⅱ) and Pd(Ⅱ2',3',4',5,7-pentahydroxy flavone

Pt(Ⅱ) and Pd(Ⅱ) complexes with 2′,3′,4′,5,7-pentahydroxy-flavone weresynthesized and characterized by elemental analysis, molar conductance, IR, ~1HNMR, TG-DTA, UV-Visspectroscopic techniques, and fluorescence analysis. The scavenging effect on the superoxide radical(O_2^-) and the inhibitory effect on lipid peroxides were also investigated. Both the ligand andthe complexes exhibit scavenging effect on superoxide radicals, and the effect of the complexes isgreater than that of the ligand. The Pt(Ⅱ) complex exhibits the strongest scavenging efficiency.Both Pt(Ⅱ) and Pd(Ⅱ) complexes have the inhibitory effect on lipid peroxides, and the effect ofthe complexes is greater than that of the ligand, but the Pt(Ⅱ) complex has a high effect ofpromoting lipid peroxides.

Temperature-Dependent Formation of Redox Sites in Molybdenum Trioxide Studied by Electron Paramagnetic Resonance Spectroscopy

The formation and qualification of redox sites in transition metal oxides are always the active fields related to electronics, catalysis, sensors, and energy-storage units. In the present study, the temperature dependence of thermal reduction of MoO3 was surveyed at the range of 350℃ to 750℃. Upon reduction, the formed redox species characterized by EPR spectroscopy are the MoVion and superoxide anion radical (O2-) when the reduction was induced at the optimal temperature of 300-350℃. When heating-up from 350℃, the EPR signals started to decline in amplitude. The signals in the range of 400-450℃ decreased to half of that at 350℃, and then to zero at ~600℃. Further treatment at even higher temperature or prolonged heating time at 500℃ caused more reduction and more free electrons were released to the MoO3 bulk, which results in a delocalized means similar to the antiferromagnetic coupling. These data herein are helpful to prepare and study the metal-oxide catalysts.

Antioxidant Activity of Pigment Extracted from Green-Wheat-Bran

The anthocyanin pigment extracted from green-wheat-bran was studied to identify its antioxidant activity.The antioxidant activities of the pigment were evaluated by anti-lipid peroxidation,total antioxidant activity （TAA）,superoxide anion radical scavenging activity （SARSA）,active oxygen scavenging activity （AOSA）,and DPPH （1,1-diphenyl-2 picrylhydrazyl free radical） radical scavenging activity.The results showed that the pigment had higher antioxidant activity and TAA,SARSA,AOSA and DPPH.scavenging activities at a certain concentration than Vc （antiscorbutic vitamin,vitamin C）,and the capacity increased with the increase of pigment concentration.Its TAA was 51.06 U mL-1,1.73 times of Vc,and SARSA 18 025.21 U mL-1,2.26% higher than Vc,and AOSA 3 776.31 U mL-1,1.24 times of Vc.As to the DPPH.scavenging activity of the pigment,there was a trend that higher concentration performed higher activity significantly improved with the company of Vc.The pigment showed significant antioxidant activities evaluated by different assays.Results will provide a better understanding on antioxidant activity of green wheat and allow the screening or breeding of green wheat varieties with higher antioxidant activity for food processing.

Decorating Ag/AgCl on UiO-66-NH2: Synergy between Ag plasmons and heterostructure for the realization of efficient visible light photocatalysis

UiO-66-NH2, as typical visible light responsive Zr-based metal-organic frameworks (MOFs), has attracted great interest in recent years. However, rapid combination of the photoinduced carriers limits its further application. Here, we designed a facile precipitation-photoreduction method to post-synthetically decorate Ag/AgCl on the surface of UiO-66-NH2 and form a heterostructure. Metallic Ag can not only transmit electrons between UiO-66-NH2 and AgCl but also absorb visible light, because of the surface plasmon resonance (SPR) effect. The rhodamine B photodegradation rate of UiO-66-NH2/Ag/AgCl (16.2 wt.% Ag) is about 10 and 4 times those of UiO-66-NH2 and Ag/AgCl, respectively. The SPR effect of Ag NPs and the formation of a heterostructure synergistically increase the absorbability of visible light, accelerate the separation of photoinduced charges, and promote the formation of superoxide radicals. We expect that our work could provide a new viewpoint for constructing efficient MOF-based photocatalytic systems.

SOD-like Activities of SOD and Cu(Ⅱ)Complexes inLiposomes

The SOD-like activities of SOD, four Cu(Ⅱ)Complexes, SOD-and Cu(Ⅱ)com-plex-liposomes were determined respectively by using cytochrome C method. The results showed that all of these systems had SOD-like activities to some extent of which the Cu(His)_2-liposome displayed the highest activity and the Cu(Ⅱ)complexes and liposomes had some positive cooperative action.