钙钛石型复合氧化物La_(1-x)Sr_xFeO_(3-λ)催化性能的研究——Ⅱ.催化剂中的活性氧种及其反应性能

用XPS、TPR和同位素交换等技术,研究了钙钛石型催化剂La_(1-x)Sr_xFeO_(3-λ)中的活性氧种及其反应性能。在考虑晶格缺陷的基础上,认为以弱键和钙钛石中氧空位给合的α氧是这个催化体系中的活性氧种。当x值自0变化至1时,α氧量增加;当x>0.4时,α氧的反应性下降。在x<0.4的范围内,催化活性取决于α氧的浓度,而在x≥0.4的范围内,催化活性取决于α氧的反应性。此外,催化活性还同该体系分解气相氧的能力有关。

甲烷氧化偶联反应稀土催化剂表面活性氧种的研究

The active oxygen species on the surface of additive/rare earth oxides (RE2O3)catalysts have been investigated by means of XPS, O2-TPD and XRD. The results indicate that there exist O and O2- species on the surface of the catalysts at low temperature. The performance of the catalyst is dependent on the concentration of O species on the catalyst surface. It is suggested that the O- species formed from O species at high temperature is active oxygen species for OCM reaction.

星形胶质细胞条件培养液对tbOOH致PC12细胞凋亡的抑制作用

目的探讨星形胶质细胞条件培养液对活性氧叔丁基脂氢过氧化物tbOOH诱导的PC12细胞凋亡的影响。方法以分离、纯化的SD大鼠大脑皮层星形胶质细胞制备的条件培养液培养tbOOH应激的PC12细胞,采用荧光显微镜和透射电镜形态观察细胞凋亡;用流式细胞术测定细胞凋亡率的变化;用巴比妥酸法评估细胞内丙二醛含量的变化。结果tbOOH可诱导PC12细胞凋亡,而星形胶质细胞条件培养液可降低其凋亡;同时,巴比妥酸法显示星形胶质细胞条件培养液可显著性降低PC12细胞丙二醛含量(P<0.05)。结论星形胶质细胞条件培养液有提高PC12细胞抗氧化能力,可抑制活性氧tbOOH诱导的神经细胞凋亡。

Antioxidase Activities of Tetraploid Lines and Diploid Control Line of Chrysanthemum cinerariifolium

Objective The SOD, POD and APX enzyme activities of tetraploid lines and diploid control line of Chrysanthemum cinerariifolium in test-tube and field were determined in order to provide a reference for the selective breeding of high resistance good tetraploid varieties of C. cinerariifolium. Method The SOD, POD and APX activities of each sample were determined. Every material should have 3 replicates which been determined and calculated mean value to analyze. Result The various kinds of antioxidase activities in protective enzyme system of tetraploid lines were increased generally in comparison with that of diploid control line. And there is certain relativity between the samples in field and in test-tube of these lines. Conclusion The antioxidase activities of each line in test-tube could be considered as reference index to screen high resistance good tetraploid varieties of C. cinerariifolium.

Generation and transformation of ROS on g-C_3N_4 for efficient photocatalytic NO removal:A combined in situ DRIFTS and DFT investigation

Understanding the performance of reactive oxygen species(ROS)in photocatalysis is pivotal for advancing their application in environmental remediation.However,techniques for investigating the generation and transformation mechanism of ROS have been largely overlooked.In this study,considering g‐C3N4 to be a model photocatalyst,we have focused on the ROS generation and transformation for efficient photocatalytic NO removal.It was found that the key to improving the photocatalysis performance was to enhance the ROS transformation from·O2^-to·OH,elevating the production of·OH.The ROS directly participate in the photocatalytic NO removal and tailor the rate‐determining step,which is required to overcome the high activation energy of the intermediate conversion.Using a closely combined experimental and theoretical method,this work provides a new protocol to investigate the ROS behavior on g‐C3N4 for effective NO removal and clarifies the reaction mechanism at the atomic level,which enriches the understanding of ROS in photocatalytic environmental remediation.

Antioxidative capacity and enzyme activity in Haematococcus pluvialis cells exposed to superoxide free radicals

The antioxidative capacity of astaxanthin and enzyme activity of reactive oxygen eliminating enzymes such as superoxide dismutase (SOD),peroxidase (POD),catalase (CAT) and ascorbate peroxidase (APX) were studied in three cell types of Haematococcus pluvialis exposed to high concentrations of a superoxide anion radical (O2ˉ).The results show that defensive enzymes and astaxanthin-related mechanisms were both active in H.pluvialis during exposure to reactive oxygen species (ROS) such as Oˉ2.Astaxanthin reacted with ROS much faster than did the protective enzymes,and had the strongest antioxidative capacity to protect against lipid peroxidation.The defensive mechanisms varied significantly between the three cell types and were related to the level of astaxanthin that had accumulated in those cells.Astaxanthin-enriched red cells had the strongest antioxidative capacity,followed by brown cells,and astaxanthin-deficient green cells.Although there was no significant increase in expression of protective enzymes,the malondialdehyde (MDA) content in red cells was sustained at a low level because of the antioxidative effect of astaxanthin,which quenched Oˉ2 before the protective enzymes could act.In green cells,astaxanthin is very low or absent;therefore,scavenging of ROS is inevitably reliant on antioxidative enzymes.Accordingly,in green cells,these enzymes play the leading role in scavenging ROS,and the expression of these enzymes is rapidly increased to reduce excessive ROS.However,because ROS were constantly increased in this study,the enhance enzyme activity in the green cells was not able to repair the ROS damage,leading to elevated MDA content.Of the four defensive enzymes measured in astaxanthin-deficient green cells,SOD eliminates Oˉ2,POD eliminates H2O2,which is a by-product of SOD activity,and APX and CAT are then initiated to scavenge excessive ROS.

The complex role of physical exercise and reactive oxygen species on brain

Reactive oxygen species （ROS） are continuously generated during aerobic metabolism and at moderate level. They play a role in redox signaling, but in significant concentration they cause oxidative damage and neurodegeneration. Because of the enhanced sensitivity of brain to ROS, it is especially important to maintain the normal redox state in different types of neuron cells. In last decade it became clear that regular exercise beneficially affects brain function, and can play an important preventive and therapeutic role in stroke, Alzheimer, and Parkinson diseases. The effects of exercise appear to be very complex and could include neurogenesis via neurotrophic factors, increased capillariszation, decreased oxidative damage, and increased proteolyfic degradation by proteasome and neprilysin. Data from our and other laboratories indicate that exercise-induced modulation of ROS levels plays a role in the protein content and expression of brain-derived neurotrophic factor, tyrosinerelated kinase B （TrkB）, and cAMP response element binding protein, resulting in better function and increased neurogenesis. Therefore, it appears that exercise-induced modulation of the redox state is an important means, by which exercise benefits brain function, increases the resistance against oxidative stress, facilitates recovery from oxidative stress, and attenuates age-associated decline in cognition.

Enhanced photocatalytic performance of MoS_2 modified by AgVO_3 from improved generation of reactive oxygen species

In this work, an efficient AgVO3/MoS 2 composite photocatalyst was successfully synthesized via a hydrothermal method. The photocatalytic activity of the as-prepared photocatalyst was evaluated by using it for assessing the degradation of different organic pollutants under visible-light irradiation. The composite 3%-AgVO3/MoS 2 catalyst demonstrated a significantly enhanced photocatalytic activity compared to the pure compounds（AgVO3 and MoS2）. The reason behind the excellent photocatalytic performance was the modification of MoS 2 by AgVO3 to facilitate O2 adsorption/activation. In addition, the composite catalyst facilitates the two-electron oxygen reduction reaction whereby H2O2 is generated on the surface of MoS 2 to produce additional reactive oxygen species（ROSs）. ESR coupled with the POPHA fluorescence detection method and a free radical capture experiment were used to elucidate the mechanism of formation of the ROSs, including ·OH, ·O2- and H2O2. Furthermore, the generation of additional ROSs could accelerate electron consumption, leaving behind more holes for the oxidation of organic pollutants. A possible photocatalytic mechanism of the composite is also discussed.

The Scavenging of Free Radical and Oxygen Species Activities and Hydration Capacity of Collagen Hydrolysates from Walleye Pollock(Theragra chalcogramma) Skin

Fish skin collagen hydrolysates （FSCH） were prepared from walleye pollock （Theragra chalcogramrna） using a mixture of enzymes, namely trypsin and flavourzyme. The degree of hydrolysis of the skin collagen was 27.3%. FSCH was mainly composed of low-molecular-weight peptides and the relative proportion of 〈1000Da fraction was 70.6%. Free radical and oxygen species scavenging activities of FSCH were investigated in four model systems, including diphenylpicrylhy-drazyl radical （DPPH）, superoxide anion radical, hydroxyl radical and hydrogen peroxide model, and compared with that of a native antioxidant, reduced glutathione （GSH）. FSCH was also evaluated by water-absorbing and water-holding capacity. The results showed that FSCH was able to scavenge free radical and oxygen species significantly and to enhance water-absorbing and water-holding capacity remarkably. Therefore FSCH may have potential applications in the medicine and food industries.

Combined effects of water temperature and copper ion concentration on catalase activity in Crassostrea ariakensis

A central composite experimental design and response surface method were used to investigate the combined effects of water temperature(18–34℃) and copper ion concentration(0.1–1.5 mg/L) on the catalase(CAT) activity in the digestive gland of C rassostrea ariakensis. The results showed that the linear effects of temperature were significant(P <0.01), the quadratic effects of temperature were significant( P <0.05), the linear effects of copper ion concentration were not significant(P >0.05), and the quadratic effects of copper ion concentration were significant(P <0.05). Additionally, the synergistic effects of temperature and copper ion concentration were not significant(P >0.05), and the effect of temperature was greater than that of copper ion concentration. A model equation of CAT enzyme activity in the digestive gland of C. ariakensis toward the two factors of interest was established, with R 2, Adj. R 2 and Pred. R 2 values as high as 0.943 7, 0.887 3 and 0.838 5, respectively. These findings suggested that the goodness of fit to experimental data and predictive capability of the model were satisfactory, and could be practically applied for prediction under the conditions of the study. Overall, the results suggest that the simultaneous variation of temperature and copper ion concentration alters the activity of the antioxidant enzyme CAT by modulating active oxygen species metabolism, which may be utilized as a biomarker to detect the effects of copper pollution.

Exercise and antioxidant supplements in the elderly

Both exercise and aging increase reactive oxygen species （ROS）, which can result in damage to cells. Aging is the result of damage caused by ROS to the mitochondrial genome in post mitotic cells and numerous studies have demonstrated an increase in ROS or their byproducts with exercise. ROS can cause oxidative stress as they overwhelm the antioxidant cellular defenses. Therefore interventions aimed at limiting or inhibiting ROS production, such as supplementation with antioxidant vitamins, should be able to reduce fatigue during muscle contraction and the rate of formation of aging changes with a consequent reduction of the aging rate and disease pathogenesis. However, it has been shown that ROS are essential signaling molecules which are required to promote the health benefits of exercise and longevity. In young individuals, ROS are required for normal force production in skeletal muscle, for the development of training-induced adaptations in endurance performance, as well as for the induction of the endogenous defense systems. Thus, taking antioxidants during training, in young athletes, seems to be detrimental. However, antioxidant supplementation may be expected to be beneficial and is receiving growing attention in the active old population. In this manuscript we review the literature associated with the main areas of interest in this topic.

Purification of Proteins from Ginkgo Biloba Seeds and Their Antioxidant Activities

Ginkgo biloba seeds were widely used for food and traditional medicine in china. In the present study, antioxidant proteins named GP were purified from Ginkgo biloba seeds. The proteins （GP） were purified by homogenization of Ginkgo biloba seeds powder in the saline solution, precipitation with 70% ammonium sulphate, and filtration on DEAE-Cellulose 52 anion exchange column. GP showed protein content of 96%, and they showed three bands with approximate molecular weight of 15 kDa, 17 kDa, 21 kDa respectively by SDS-PAGE electrophoresis analysis. Compositions of amino acids obtained by Amino Acid Analyzer showed GP were rich in Glu, Ser ,His ,Asp, Gly, Ala, Leu and Lys compared with the other fractions. The antioxidant activities of GP were investigated using DPPH （the 1, 1-diphenyl-2-picrylhydrazyl） free radical-scavenging and ferric-reducing antioxidant power assays. The GP showed antioxidant activities higher than α-Tocopherol and BHA. Therefore, the present study demonstrates proteins from Ginkgo biloba seeds （GP） can be excellent antioxidant.

Alterations of Antioxidative Enzymes Activities and Induction of Lipid Peroxidation in Germinating Wheat Seeds Subjected to Cadmium Stress

Germinating wheat （Triticum aestivum L.） seeds were exposed to CdCI2 （50, 100 and 200 μM） for 48 h and some aspects of oxidative metabolism was assessed in the embryonic tissues. The germination percentage and the soluble protein content of the embryonic tissues were found to decrease with increasing of Cd concentration. There was elevation in superoxide dismutase （SOD） and decline in catalase （CAT） and peroxidase （POX） activities. The increasing of lipid peroxidation levels indicated the prevalence of oxidative stress in the tissues which was probably due to the alteration of antioxidative enzymes activities. The adding of ascorbate, along with CdCl2, has resulted in restoration of the Cd induced decline in CAT activity. Weakening in H2O2 detoxification system seems to be the principal reason behind Cd induced oxidative stress in germinating seeds. Thus, imposition of oxidative stress might be the consequence of cadmium stress and this finding may help in elucidating the mechanisms underlying cadmium mediated toxicity in germinating seeds.

Analysis on Carotenoids Content and Other Quality Traits of 185 Wheat Varieties

In order to provide the reference of improving the nutritional quality traits in carotenoids and screening its resources of wheat varieties, 185 wheat varieties or lines were selected as materials to test the carotenoids content, lipoxygenase activity, whiteness, yellowness and some other quality traits of whole mill in wheat.The results showed that there were highly significant variations in lipoxygenase activity,carotenoids content, whiteness and yellowness among those sample of wheat varieties; carotenoids content was significantly and positively correlated with yellowness.Cluster analysis was performed based on carotenoids content clustered all the varieties or lines into three major groups. Additionally, carotenoids were discussed in the application of nutritional quality improvement in wheat.

Polyphenol Oxidase Activity and Inhibition in White Yam （Dioscorea Rotundata. Var. Laasirin） Chips as African Fries for Human Consumption

Polyphenol oxidase, a bi-functional enzyme, has been implicated in enzymatic browning of yam and other tubers in a negative way. The objective of this present study was to examine the activity of polyphenol oxidase in Dioscorea rotundata. Var. laasirin and the efficiency of heat and chemical treatments in inhibiting this enzyme. Crude Polyphenol Oxidase （PPO） of Dioscorea rotundata.Var. Laasirin was isolated and the kinetics studied using the lineweaver-burk plot. The activity of the enzyme was evaluated using spectrophotomeric method. Yam PPO catalyzes oxidation of various substrates with catechol being the most readily oxidized substrate. The Michaelis-Menten constant （Km） and maximum reaction velocity （Vmax） for yam PPO were 0.00037 and 0.3125 respectively. Inhibition data showed that the enzyme had least activity （71.70） when blanched at 95℃ for 7 mins with chemical treatment involving a combination of 0.5% Sodium metabisulphite （Food grade） and 0.5% Ascorbic acid （Food grade）. The activity was highest （83.02） when it was blanched at 95 ℃ for 7 rains. This study has shown that it is possible to inhibit polyphenol oxidase activity in white yam using the chemical pretreatments and processing conditions described in this study for possible adoption in the production of packaged frozen yam chips by food industries.

过渡金属-铈复合氧化物对碳烟的催化燃烧性能和表征

采用共沉淀法制备了不同过渡金属(Fe、V、Mn、Co、Cu)和铈的复合体氧化物催化剂,并用程序升温还原法(H2-TPR)、BET、XRD、拉曼光谱(RS)和光电子能谱(XPS)对催化剂进行了表征.同时,利用热重法测试了催化剂对碳烟的催化活性.实验结果表明,过渡金属的添加极大地提高了氧化铈的催化活性,其中,铈铁复合氧化物的催化活性最高.催化剂催化燃烧碳烟的活性与催化剂表面的耗氢量以及催化剂表面氧种OⅡ的含量紧密相关.

紫外辐射的细胞生物学效应及其机制

地球表面的生物体会受到来自阳光紫外辐射的照射。两极臭氧层空洞的形成使地球表面的紫外辐射水平,特别是UVB的水平增加,进而对生物体的危害日益加重。因此,深入研究紫外辐射生物学效应的信号转导机制并阐明其损伤机制和生物体的反应机制等具有重要意义,也可为紫外辐射损伤防护的研究提供新思路。本文综述了本领域近年来的相关研究,从紫外辐射所致生物学效应的信号转导机制(包括对DNA的直接损伤作用、细胞膜激酶和非激酶受体通路、细胞质通路以及microRNA)等方面对紫外辐射的损伤机制进行了比较系统的阐述和总结。

Realgar induces differentiation through ROS-dependent mitochondrial pathway in HL-60 cells

Realgar （As 4 S 4 ）, as a mineral drug in traditional Chinese medicine, is currently used as the remedy for acute promyelocytic leukemia and has been proven to have relatively milder side effects as compared to the arsenolite （As 2 O 3 ）-based drugs. We have previously demonstrated that realgar induces differentiation in HL-60 cells, and the differentiation is associated with serine/threonine protein phosphatases, MAPK signaling pathways, and mitochondrial transmembrane potential decrease. In this study, we further explore the roles of mitochondrial permeability transition pore and reactive oxygen species （ROS） in realgar-induced differentiation in HL-60 cells. The differentiation was preceded by marked changes in the cellular level of ROS, and could be enhanced by SB202190, a p38 MAPK inhibitor. In addition, the efficacy of realgar was suppressed by closing the MPTP with an inhibitor. Taken together, these findings indicate that the opening of MPTP and the alteration of ROS generation were involved in realgar-induced differentiation.

Vanadium compounds induce stronger growth suppression in PTEN-deficient prostate cancer cells by ROS-mediated mechanism

In the present study, we investigated the antiproliferative effect and the underlying mechanism of three antidiabetic vanadium compounds, metavanadate, VO（acac）2 and VO（ma）2, in human prostate cancer cells （PC-3 and DU-145）. The results showed that vanadium compounds caused cell cycle arrest at G2/M phase evidenced by the elevation ofphosphorylated Cdc2 at tyr-15. Moreover, the results revealed that vanadium compounds induced reactive oxygen species （ROS） elevation in the two cell lines. The decreased level of Cdc25C could be rescued by the antioxidant, N-acetylcysteine, indicating that vanadium compounds-induced G2/M arrest was mediated by ROS. Additionally, the three vanadium compounds exerted more potent growth inhibitory effect on PC-3 cells which are PTEN-deficient and with higher level of basal ROS. It suggested that PTEN protein might serve as a biomarker for the selectivity of antitumor therapy using ROS-generating agents. Since the studied vanadium compounds have been shown the antidiabetic activities in the previous studies, there may be additional benefits in the potential application of vanadium compounds to suppress the growth of prostate cancer cells.

Gadolinium-promoted angiogenesis involves the activation of PKCα/β_2 and MAPKs in human umbilical vein endothelial cells

Gadolinium has been widely used as a contrast agent for magnetic resonance imaging in clinical practice. Recently, it was reported that gadolinium is involved in nephrogenic systemic fibrosis, although the exact mechanism by which gadolinium triggers nephrogenic systemic fibrosis remains unclear. In this study, we show that gadolinium chloride （GdC13） induced human umbilical vein endothelial cells （HUVECs） to migrate in Matrigel and tubulogenesis during wound healing. Chick chorioallantoic membrane assay confirmed that GdC13 stimulates angiogenesis. Under the optimal angiogenic concentration of GdC13 （1 0 ~tM）, intracellular calcium concentration and reactive oxygen species generation were elevated. Moreover, western blotting results indicate that in cells treated with GdC13, Ca2＋-dependent PKCa/132 was phosphorylated, and MAPKs pathways were also activated. Taken together, GdC13 has a potential effect on angiogenesis in HUVECs, and the possible mechanisms may involve oxidative stress and calcium-related signalin~ pathways.