麦胚蛋白酶解物对小鼠抗氧化作用的研究

研究不同剂量麦胚蛋白酶解物WGPHs对小鼠抗氧化作用的影响。80只昆明系小鼠,雌雄各半,分为基础饲料对照大组和高脂饲料对照大组,各大组随机分为四小组,分别为对照组、WGPHs低剂量组、WGPHs中剂量组、WGPHs高剂量组。对照组灌胃生理盐水,其余三组分别按100、500、1000mg/kg·d的剂量灌胃WGPHs水溶液。各组连续灌胃30d后,处死小鼠,检测小鼠血清超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)活性以及丙二醛(MDA)含量。结果表明:WGPHs在显著提高小鼠血清SOD和GSH-Px活性(p<0.05)的同时能显著降低血清MDA含量(p<0.05),其作用效果随着WGPHs剂量的增加而增大,WGPHs可增强小鼠的抗氧化作用。     

库车小白杏混菌乳酸发酵工艺优化及其发酵动力学模型

采用响应面分析法的4因子中心组合实验设计（Central composite experimental design,CCD）优化了库车小白杏混菌（植物乳杆菌和罗伊氏乳杆菌）乳酸发酵工艺,并采用Logistic方程建立乳酸菌生长和超氧化物歧化酶（Superoxide dismutase,SOD）活性的动力学模型。结果表明,最佳发酵工艺为:温度为37.0 ℃,植物乳杆菌:罗伊氏乳杆菌配比为2.6:1,接种量为5.0%,发酵时间为30 h。在此条件下,杏汁中的SOD活性为309.60 U/g,感官评分为54.18分;动力学模型的预测值与实验值的拟合度分别为0.9970、0.9913,说明拟合曲线与乳酸菌生长量和SOD活性的实验数据有很高的相关性,能很好地模拟小白杏乳酸发酵过程的动力学特性。     

常见蔬菜消除超氧阴离子作用的研究

用核黄素光化学氧化光度法研究了南瓜、玉米、大蒜、苦瓜、空心菜、西红柿、胡萝卜、韭菜花8种常见蔬菜对超氧阴离子的消除作用。结果表明这些蔬菜均具有消除超氧阴离子的作用;煮沸20min,玉米和南瓜的消除超氧阴离子能力减弱约30％,空心菜的有所上升,而大蒜、苦瓜、西红柿、胡萝卜、韭菜花的消除作用均没有变化。将吸光度随这八种蔬菜提取液加入量的变化趋势与维生素C的相比较,提出蔬菜消除超氧阴离子的作用主要是依靠维生系C以外的超氧化物歧化酶等物质。     

Superoxide Dismutase as a Novel Macromolecular Nitric Oxide Carrier: Preparation and Characterization

Nitric oxide (NO) is an important molecule that exerts multiple functions in biological systems. Because of the short-lived nature of NO, S-nitrosothiols (RSNOs) are believed to act as stable NO carriers. Recently, sulfhydryl (SH) containing macromolecules have been shown to be promising NO carriers. In the present study, we aimed to synthesize and characterize a potential NO carrier based on bovine Cu,Zn-superoxide dismutase (bSOD). To prepare S-nitrosated bSOD, the protein was incubated with S-nitrosoglutathione (GSNO) under varied experimental conditions. The results show that significant S-nitrosation of bSOD occurred only at high temperature (50 °C) for prolonged incubation time (>2 h). S-nitrosation efficiency increased with reaction time and reached a plateau at ~4 h. The maximum amount of NO loaded was determined to be about 0.6 mol SNO/mol protein (~30% loading efficiency). The enzymatic activity of bSOD, however, decreased with reaction time. Our data further indicate that NO functionality can only be measured in the presence of extremely high concentrations of Hg²⁺ or when the protein was denatured by guanidine. Moreover, mildly acidic pH was shown to favor S-nitrosation of bSOD. A model based on unfolding and refolding of bSOD during preparation was proposed to possibly explain our observation.     

Copper(I)-Dioxygen Adducts and Copper Enzyme Mechanisms

Primary copper(I)-dioxygen (O₂) adducts, cupric-superoxide complexes, have been proposed intermediates in copper-containing dioxygen-activating monooxygenase and oxidase enzymes. Here, mechanisms of C−H activation by reactive copper-(di)oxygen intermediates are discussed, with an emphasis on cupric-superoxide species. Over the past 25 years, many synthetically derived cupric-superoxide model complexes have been reported. Due to the thermal instability of these intermediates, early studies focused on increasing their stability and obtaining physical characterization. More recently, in an effort to gain insight into the possible substrate oxidation step in some copper monooxygenases, several cupric-superoxide complexes have been used as surrogates to probe substrate scope and reaction mechanisms. These cupric superoxides are capable of oxidizing substrates containing weak O−H and C−H bonds. Mechanistic studies for some enzymes and model systems have supported an initial hydrogen-atom abstraction via the cupric-superoxide complex as the first step of substrate oxidation.     

Nd3＋、Er3＋、Gd3＋和La3＋对超氧化物歧化酶活性的影响

通过研究Nd3＋、Er3＋、Gd3＋和La3＋稀土离子对枯草芽孢杆菌在生长过程中所产的超氧化物歧化酶活性的影响,来探讨稀土可能会导致生物体发生氧化损伤。利用改良的邻苯三酚自氧化法测定超氧化物歧化酶活性。结果表明：4种稀土离子对其细胞中超氧化物歧化酶活性均有抑制作用,且Nd3＋的抑制作用较其它3种稀土离子要强,故一定浓度的稀土离子很有可能会导致生物体发生氧化损伤。4种稀土离子的浓度不同影响有所不同,总的来说,稀土离子的浓度越大,对枯草杆菌抗氧化的抑制作用越明显,损伤毒性作用越强。     

超氧化物歧化酶益生菌发酵酸奶的研究

本文研究了在不同的益生菌发酵剂配比条件下酸奶的品质和口感.双歧杆菌:嗜酸乳杆菌:保加利亚乳杆菌:嗜热链球菌比例为(10∶4∶2∶2)用于酸奶的混合发酵生产,可以使双歧杆菌活菌数达到1.5×108cfu/ml、嗜酸乳杆菌活菌数达到3.1×108 cfu/ml;采用添加低聚木糖等益生元,可以促进双歧杆菌的活菌数目提高;发酵后在LABS酸奶中添加SOD,可保持其在酸奶中较高的酶活力.SOD-LABS益生菌酸奶在4℃保存21d,SOD酶活性能保持75%以上.     

Dynamic Changes in Reactive Oxygen Species in the Shoot Apex Contribute to Stem Cell Death in Arabidopsis thaliana

In monocarpic plants, stem cells are fated to die. However, the potential mechanism of stem cell death has remained elusive. Here, we reveal that the levels of two forms of reactive oxygen species (ROS), superoxide anion free radical (O2·−) and hydrogen peroxide (H₂O₂), show dynamic changes in the shoot apex during the plant life cycle of Arabidopsis thaliana. We found that the level of O2·− decreased and disappeared at four weeks after bolting (WAB), while H₂O₂ appeared at 3 WAB and showed a burst at 5 WAB. The timing of dynamic changes in O2·− and H₂O₂ was delayed for approximately three weeks in clv3-2, which has a longer lifespan. Moreover, exogenous application of H₂O₂ inhibited the expression of the stem cell determinant WUSCHEL (WUS) and promoted the expression of the developmentally programmed cell death (dPCD) marker gene ORESARA 1 (ORE1). These results indicate that H₂O₂ triggers an important signal inducing dPCD in stem cells. Given that O2·− plays roles in maintaining WUS expression and stem cell activity, we speculate that the dynamic shift from O2·− to H₂O₂ in the shoot apex results in stem cell death. Our findings provide novel insights for understanding ROS-mediated regulation during plant stem cell death.