天然食品对自由基的清除能力

对 2 9种天然食品提取物的自由基 ( .OH)清除能力进行评价 ,结果显示海带具有最高的自由基清除能力 ,而且具有自由基清除能力的成份稳定性较高 ,加热、冷藏、活性炭处理、硅藻土处理对其自由基清除能力影响较小 ,当海带 :甘草 :枸杞 :红枣 =10∶ 1∶ 1∶ 1( V/V)时 ,其自由基清除能力大大提高 ,显示了 4种天然食品在一定比例下具有协同增效作用     

豨莶草叶浸提液对羟基自由基的清除作用

[目的]研究豨莶草叶浸提液对羟基自由基(·OH)的清除作用,为豨莶草资源的药用开发提供参考依据.[方法]采用水浴回流法制备豨莶草叶浸提液,通过单因素试验和正交试验,确定豨莶草叶浸提液清除·OH效果最佳的浸提工艺条件.[结果]影响豨莶草叶浸提液清除·OH效果的因素顺序为:料液比>乙醇体积分数>水浴温度>浸提时间,其最佳浸提工艺条件:以80%乙醇为浸提剂,在料液比1∶10.0、60℃水浴回流条件下浸提2.0 h,·OH清除率为91.7%;豨莶草叶浸提液体积为1.00 mL时,·OH清除率达92.6%.[结论]豨莶草叶浸提液具有一定的抗氧化性,可作为天然抗氧化剂资源进一步研究.     

儿茶素对羟自由基诱发SOD基因序列改变的影响

利用基因克隆与测序技术,研究了儿茶素对羟自由基诱发SOD基因序列改变的影响,结果表明：Fe(Ⅱ)/H₂O₂产生的羟自由基可诱导西红柿叶片SOD基因中G→A,G→C间的颠换,且Fe(Ⅱ)浓度越高,颠换率越高,尤其是G→C的颠换,但儿茶素的加入明显抑制这种颠换,且(一)-EGCG＞(一)-ECG＞(一) -EGC＞ (一)-EC,呈浓度—效应关系,而儿茶素本身不能使SOD基因发生碱基颠换。     

Rate constants for the reactions of hydroxyl and hydroperoxyl radicals with ozone

Chain decomposition of ozone by hydroxyl and hydroperoxyl radicals has been observed. The rate constant at 3000 degrees K for OH + O(3)-->HO(2) + O(2) is 8 x 10(-14) cubic centimeters per second. The rate constant for HO(2) + O(3)--> OH + 2O(2), is 3 x 10(-15) cubic centimeters per second. These results have implications concerning stratospheric ozone.     

罗望子壳总黄酮提取及其清除羟基自由基活性研究

[目的]优化罗望子壳总黄酮的提取工艺条件,并研究其对羟基自由基（·OH）的清除活性,为罗望子的药用开发提供科学参考.[方法]以罗望子壳为材料、乙醇为提取剂,通过单因素试验和正交试验,考察乙醇体积分数、料液比（g∶mL）、浸提温度、浸提时间对罗望子壳总黄酮提取率的影响,以优化罗望子壳总黄酮提取工艺条件;并以二丁基羟基甲苯（BHT）为对照,初步探究罗望子壳总黄酮提取液对·OH的清除活性.[结果]影响罗望子壳总黄酮提取效果的主要因素是浸提温度,其次是料液比和乙醇体积分数,浸提时间对罗望子壳总黄酮提取效果的影响相对较小;罗望子壳总黄酮最佳提取工艺条件为：乙醇体积分数75％,料液比1∶40,浸提温度80℃,浸提时间2.0h,在此条件下罗望子壳总黄酮提取率为2.700％.罗望子壳总黄酮提取液对·OH清除活性高于相同质量浓度的BHT.[结论]乙醇浸提法是提取罗望子壳总黄酮的有效办法,且提取获得的总黄酮对·OH具有较强的清除能力.     

Rate of gas phase association of hydroxyl radical and nitrogen dioxide

The reaction of OH and NO(2) to form gaseous nitric acid (HONO(2)) is among the most influential in atmospheric chemistry. Despite its importance, the rate coefficient remains poorly determined under tropospheric conditions because of difficulties in making laboratory rate measurements in air at 760 torr and uncertainties about a secondary channel producing peroxynitrous acid (HOONO). We combined two sensitive laser spectroscopy techniques to measure the overall rate of both channels and the partitioning between them at 25°C and 760 torr. The result is a significantly more precise value of the rate constant for the HONO(2) formation channel, 9.2 (±0.4) × 10(-12) cm(3) molecule(-1) s(-1) (1 SD) at 760 torr of air, which lies toward the lower end of the previously established range. We demonstrate the impact of the revised value on photochemical model predictions of ozone concentrations in the Los Angeles airshed.     

Evidence for substantial variations of atmospheric hydroxyl radicals in the past two decades

The hydroxyl radical (OH) is the dominant oxidizing chemical in the atmosphere. It destroys most air pollutants and many gases involved in ozone depletion and the greenhouse effect. Global measurements of 1,1,1-trichloroethane (CH3CCl3, methyl chloroform) provide an accurate method for determining the global and hemispheric behavior of OH. Measurements show that CH3CCl3 levels rose steadily from 1978 to reach a maximum in 1992 and then decreased rapidly to levels in 2000 that were lower than the levels when measurements began in 1978. Analysis of these observations shows that global OH levels were growing between 1978 and 1988, but the growth rate was decreasing at a rate of 0.23 +/- 0.18% year(-2), so that OH levels began declining after 1988. Overall, the global average OH trend between 1978 and 2000 was -0.64 +/- 0.60% year(-1). These variations imply important and unexpected gaps in current understanding of the capability of the atmosphere to cleanse itself.     

羟自由基氧化对鲢鱼糜凝胶品质的影响

以冷冻鲢鱼糜为研究对象,用芬顿体系(H_2O_2的浓度分别为0.1,1.0,5.0,10.0和50.0 mmol/L)产生不同浓度的羟基自由基对其进行模拟氧化,研究冷冻鱼糜贮藏过程中氧化程度对鱼糜品质的影响。结果表明:随着H_2O_2浓度的增大,鱼糜的破断力、凹陷深度、凝胶强度和持水性都呈现先增加后降低的趋势,在H_2O_2浓度为1.0 mmol/L时均达到最大值;鱼糜凝胶水分状态分布中T_(22)峰面积也在H_2O_2浓度为1.0 mmol/L时达到最大值;Ca~(2+)-ATPase活性随着H_2O_2浓度的增大呈现先显著增大后降低的趋势;鱼糜凝胶的扫描电镜图片显示,适度氧化(H_2O_2浓度为0.1～1.0 mmol/L)的鱼糜凝胶拥有更加致密的网络结构,具有较小的孔隙,而过度氧化(H_2O_2浓度为10～50 mmol/L)又会导致网络结构的破坏。     

Atmospheric trends in methylchloroform and the global average for the hydroxyl radical

Frequent atmospheric measurements of the anthropogenic compound methylchloroform that were made between 1978 and 1985 indicate that this species is continuing to increase significantly around the world. Reaction with the major atmospheric oxidant, the hydroxyl radical (OH), is the principal sink for this species. The observed mean trends for methylchloroform are 4.8, 5.4, 6.4, and 6.9 percent per year at Aldrigole (Ireland) and Cape Meares (Oregon), Ragged Point (Barbados), Point Matatula (American Samoa), and Cape Grim (Tasmania), respectively, from July 1978 to June 1985. These measured trends, combined with knowledge of industrial emissions, were used in an optimal estimation inversion scheme to deduce a globally averaged methylchloroform atmospheric lifetime of 6.3 (+ 1.2, -0.9) years (1sigma uncertainty) and a globally averaged tropospheric hydroxyl radical concentration of (7.7 +/- 1.4) x 10(5) radicals per cubic centimeter (1sigma uncertainty). These 7 years of gas chromatographic measurements, which comprise about 60,000 individual calibrated real-time air analyses, provide the most accurate estimates yet of the trends and lifetime of methylchloroform and of the global average for tropospheric hydroxyl radical levels. Accurate determination of hydroxyl radical levels is crucial to understanding global atmospheric chemical cycles and trends in the levels of trace gases such as methane.     

Atmospheric hydroxyl radical production from electronically excited NO2 and H2O

Hydroxyl radicals are often called the "detergent" of the atmosphere because they control the atmosphere's capacity to cleanse itself of pollutants. Here, we show that the reaction of electronically excited nitrogen dioxide with water can be an important source of tropospheric hydroxyl radicals. Using measured rate data, along with available solar flux and atmospheric mixing ratios, we demonstrate that the tropospheric hydroxyl contribution from this source can be a substantial fraction (50%) of that from the traditional O(1D) + H2O reaction in the boundary-layer region for high solar zenith angles. Inclusion of this chemistry is expected to affect modeling of urban air quality, where the interactions of sunlight with emitted NOx species, volatile organic compounds, and hydroxyl radicals are central in determining the rate of ozone formation.     

胶网藻1A10营养成分及羟基自由基清除能力研究

为更好地开发胶网藻(Dictyosphaerium sp.1A10)在食品及饲料方面的潜力,以胶网藻(Dictyosphaerium sp.1A10)为实验对象,分析了其营养成分和羟基自由基清除能力。结果显示:藻粉中含有丰富的多糖、油脂、灰分、粗纤维、蛋白质,分别占藻粉干重的19.15%、24.56%、12.43%、12.31%和18.55%,其能量为371 kcal;藻粉中含有较高的亚油酸和亚麻酸,质量分数分别为油脂的15.3%和8.5%;藻粉含18种氨基酸,含量为10.16%,其中8种必需氨基酸占3.2%,且氨基酸的比值系数分(SRCAA)较高;藻粉中还含有7种维生素,其中VB1、VB3、VB6、VA和VE的含量较高,分别为2.15 mg/100 g、6.25 mg/100 g、1.31 mg/100g、2.37 mg/100 g和5.28 mg/100 g;藻粉中矿物元素镁、钙、铁、钾含量较高,分别为3 517.26 mg/kg、813.27mg/kg、301.78 mg/kg和9 426.87 mg/kg。采用电子顺磁共振技术检测到胶网藻1A10对羟基自由基有较强的清除作用,自由基清除率达62.62%。胶网藻1A10具有开发成为食品和饲料的潜力。     

Mitochondrial transformation in yeast by bombardment with microprojectiles

The genetic transformation of mitochondria and chloroplasts has been an intractable problem. The newly developed "biolistic" (biological ballistic) process was used to deliver DNA into yeast cells to stably transform their mitochondria. A nonreverting strain, which is respiratory deficient because of a deletion in the mitochondrial oxi3 gene, was bombarded with tungsten microprojectiles coated with DNA bearing sequences that could correct the oxi3 deletion. Respiratory-competent transformants were obtained in which the introduced oxi3 DNA is integrated at the homologous site in the mitochondrial genome. Organelle genomes can now be manipulated by molecular genetic techniques in the same way as nuclear genomes.     

以基因枪法转化日本结缕草获得转基因植株

将含有DREB1A和gus基因的双基因载体质粒包裹在金粉上,以基因枪轰击日本结缕草胚性愈伤组织,以gus基因的瞬时表达研究日本结缕草基因枪转化参数.结果表明, 在1 100 psi压力下6 cm的轰击距离、每皿轰击2次的转化效果最好,而金粉和质粒用量对转化效率影响不显著;经过筛选和再生培养,检测到gus基因的稳定表达,并获得日本结缕草潮霉素抗性株系,PCR-Southern杂交证实外源DREB1A基因已整合到日本结缕草基因组中.      

玉米基因枪法把五个不同基因共转移的研究

采用基因枪法把五个不同基因p35sGFP、pA ctG us、pU b iLuc、p35sPatP IV 4、pAH 2转移到玉米幼胚愈伤组织,以研究基因共转移的某些特性。试验结果表明,在处理B 1、B 2、B 3和B 4中,共获得转基因再生植株34株,分别涉及73、46、80和109个玉米幼胚愈伤组织,其基因转移频率分别是30.14%、17.39%、1.25%和2.75%。在基因转移中,一个幼胚愈伤组织一般可以获得一株转基因植株,同时也存在一个幼胚愈伤组织可以获得3株或以上的转基因植株的可能性。此外,有70%的机率能把3~4个不同基因进行至少一次克隆后共转移整合到玉米转基因再生植株上,而把五个不同基因共转移整合到玉米转基因再生植株上的机率则很低。不同基因的大小和质量会影响克隆的频率。已经整合到玉米转基因再生植株基因组上的转移基因的表达频率达到50%以上,不表达的转移基因则可能是基因沉默现象。     

Tropomyosin paracrystals formed by divalent cations

Rabbit tropomyosin exhibits a polymorphism dependent on divalent cations and pH. Above a critical divalent cation concentration fibers with a period of about 400 angstroms are formed. Below this concentration, and near the isoelectric point, lattices are formed. Implications for the morphology and function of striated and smooth muscle are discussed.     

棉纤维起始分化期基因枪介导的GhSuSy表达分析

蔗糖合酶(sucrose synthase)通过调节植物糖代谢介导棉纤维的起始和发育。为进一步研究棉纤维起始分化过程中蔗糖合酶的转录调控机制,克隆了GhSuSy基因5′端上游2 000 bp的启动子片段,构建了含LUC荧光报告基因的重组载体,采用基因枪瞬时转化技术,把重组载体DNA分别转化到棉花叶片和花瓣,比较分析了不同载体膜压力、不同轰击距离与孵育时间等条件下的荧光素酶(luciferase, LUC)活性。用优化后的条件检测了棉纤维起始分化期蔗糖合酶基因GhSuSy偶联的LUC在叶片和花瓣中的活性,并与GhSuSy表达、蔗糖合酶活性比较分析。结果显示：-0.09 MPa真空度下,可裂膜压力设为6.80 MPa,载体膜距离叶片7 cm,轰击2次转化效率最高,转化后样品孵育16 h左右LUC荧光信号最强;与叶片中LUC表达相比,花瓣中LUC荧光信号强、活性高,特别是开花当天(0 d)和开花后1 d(1 DPA)差异明显;在纤维起始分化的开花前3 d(-3 DPA)到开花后3 d(3 DPA),叶片和花瓣中LUC活性先升高后降低,在0和1 DPA的LUC活性最高,这一结果与GhSuSy的...     

Solution photochemistry of thymine and uracil

With dienes as specific triplet quenchers, it has been shown that the photodimerization of thymine in acetonitrile proceeds entirely through the triplet state and the photodimerization of uracil in acetonitrile or in water proceeds in part through the triplet state. The photohydration of uracil probably does not involve the triplet state. Efficiencies of intersystem crossing of thymine and uracil in acetonitrile were determined.     

非复制型尿嘧啶营养缺陷型弓形虫刺激雏鸡胸腺细胞的转录组学分析

为研究非复制型尿嘧啶营养缺陷型弓形虫（Nonreplicating Toxoplasma uracil auxotrophs,NRTUAs）在转录组水平对雏鸡胸腺的免疫调节作用,本研究以接种NRTUAs虫株3 d的雏鸡为试验对象,利用RNA-seq技术对其胸腺组织进行转录组测序以挖掘其中的差异表达基因（DEGs）,进而对得到的DEGs进行GO功能注释、KEGG信号通路富集分析和蛋白互作网络分析。结果表明：1）筛选出964个DEGs,其中517个基因表达上调,447个表达下调。2）通过GO功能注释发现差异基因在生物过程、细胞组分和分子功能三大类别显著富集在免疫应答、防御反应、对外界刺激反应、对刺激反应、细胞外区域、细胞表面等条目。3）KEGG信号通路富集分析发现DEGs显著集中在细胞因子及其受体相互作用、IgA产生的肠道免疫网络、细胞粘附分子、Toll样受体信号通路等通路上。4）通过蛋白互作网络分析发现9个重要的关键分子,其中IL-6和IL-18具有调节细胞分化促进干扰素产生的功能,IRF1和IRF7能够调节巨噬细胞等细胞的活化以及抗原递呈能力,SOCS1能够防止STAT1信号通路异常活跃而导致的过度炎症反应,CCL4、CCR5和CCL20作为趋化因子能够诱导多种免疫细胞浸润炎症区域,CD40能够增强抗原递呈进而调节机体的免疫功能。综上,NRTUAs虫株刺激雏鸡胸腺后,胸腺细胞的增殖活动减弱,T细胞活化以及细胞因子分泌等活动增强,并且IL-6、IL-18、IRF1、IRF7、SOCS1、CCL4、CCR5、CCL20和CD40是NRTUAs虫株调节雏鸡胸腺细胞的重要分子,本研究为深入探讨NRTUAs虫株调节家禽胸腺的先天性免疫反应的分子机制提供了理论依据。