锌电沉积与丙烯酸盐聚合的复合过程

锌电沉积与丙烯酸盐聚合的复合过程姚素薇廖川平＊郭鹤桐（天津大学应用化学系天津３０００７２）关键词电沉积，电聚合，复合镀层，聚合物膜１９９６－０６－０７收稿，１９９６－０８－０９修回国家自然科学基金资助课题让锌的电沉积与丙烯酸盐的电化学引发自由基聚合［...     

天然铜－锌超氧化物歧化酶的电化学行为的研究

天然铜－锌超氧化物歧化酶的电化学行为的研究韩吉林，陈洪渊，钱雯，金生浩（南京大学化学系，南京，２１００９３）（南京医科大学）关键词铜－锌超氧化物歧化酶，极谱法，伏安法超氧化物歧化酶（ＳＯＤ）是一种广泛存在于生物体内的金属酶，它能够催化超氧阴离子自由基...     

有益微量元素与衰老

鉴于异常自由基反应及其与衰老的关系,以及微量元素在催化或抑制自由基反应和清除反应中产生的有害物质方面的作用,微量元素硒、锌及结合于酶中硒、锌、锰、铜对延缓衰老起积极作用。解脱"隔室封闭"的铁,可能还有铜离子,则可催化自由基反应,加速衰老过程。     

取代基对氮和氧自由基稳定性影响的理论研究

用MNDO方法，全构型优化，研究了15个氮自由基4-RC6H4NH，和15个氧自由基4-RC6H4O（R＝－H；－OCH3，－Cl，－F，－CN，－COCH3，－NO2，－CH3，－CF3，－SCH3，－C6H5，－Nh2，－BH2，－PH2，－SiH3）的稳定化能．结果表明：－NH2，－CH3，－OCH3，－F基团对自由基起稳定化作用，－CF3，－NO2；－CN，－COCH3，－BH2基团对自由基起去稳定化作用．苯基对氧自由基有较大的稳定化作用，而对氮自由基的稳定性影响较小．－SCH3，－PH2，－SiH3，－Cl基团表现弱的去稳定化作用．计算和实验结果基本相符．     

儿童发锌含量差异对血红蛋白及铜代谢的影响

分析测定了３４６名儿童的发锌（Ｚｎ）、发铜（Ｃｕ）含量，从中抽出发锌含量大于１００×１０－６和小于６０×１０－６的两组儿童进行比较，发现高锌儿童的血红蛋白（Ｈｂ）含量显著高于低锌儿童；身高、体重等代表体格发育的指标明显不同，高锌组儿童发育明显优于低锌组．说明发锌含量高低直接影响到儿童造血功能及发育水平．另外高锌组的发铜含量比低锌组低，两组μｕ／Ｚｎ比值有显著性差异，锌的高含量对铜的代谢有一定影响，锌对铜具有拮抗作用．     

以杂环为铁磁耦合单元的双中心双自由基高自旋有机分子的理论设计

利用－·N－S－为自旋中心（SC），苯为端基（EG），苯、吡啶、哒嗪、嘧啶 、吡嗪、三嗪为耦合单元（FC），设计三种不同排列方式的新型稳定高自旋分子。 由于自旋密度在杂环（FC）和－·N－S－（SC）组成的体系中自由基双中心的部分 离域，导致－·N-S－自由基的特殊稳定性。三种不同的排列方式中，其三重态的 稳定性随主要SC（－N－）原子间距离的增大而降低。从三个系统八个体系三重态 的稳定性来看，FC上的杂原子位于取代基的间位能提高体系的铁磁耦合作用，而位 于邻位和对位则不利于铁磁耦合作用。     

β－CD对Zn（Ⅱ）－m－BrTPPS_4显色反应增敏作用的研究

本文系统研究了β－ＣＤ对Ｚｎ（Ⅲ）－ｍ－ＢｒＴＰＰＳ＿４显色体系的增敏作用，提出了高灵敏度测定痕量锌的分光光度新方法。显色体系的表观摩尔吸光系数为４．５７×１０￣５Ｌ·ｍｏｌ￣（－１）·ｃｍ￣（－１），Ｚｎ（Ⅱ）的浓度在０～５μｇ／２５ｍＬ符合比尔定律。应用本法于人发、铝合金等试样中锌的测定，回收率及方法对照结果令人满意。     

壳聚糖固定化N-亚水杨基甘氨酸锌Schiff碱配合物的研究

利用天然高分子聚合物壳聚糖的轴向配位能力, 首次合成了壳聚糖-N-亚水杨基甘氨酸Schiff碱锌配合物, 通过元素分析、紫外吸收光谱、红外吸收光谱和热分析等方法对配体及配合物进行了表征, 推测了配合物的结构组成. 以Pyrogallol-NBT比色法测定了合成配合物对超氧阴离子自由基的清除能力. 结果表明, 壳聚糖固定化N-亚水杨基甘氨酸锌Schiff配合物对超氧阴离子自由基的清除能力与水杨醛锌Schiff配合物相比大致一样, 但毒性较小.     

儿童锌营养缺乏症的流行病学调查

对390例有锌营养缺乏表现的0～6岁儿童．进行发锌检测及锌营养缺乏的相关因素分析。结果表明与无锌营养缺乏表现的儿童相比，缺锌率分别是90．6％及37％，发锌均值分别是78.8×10-6±17.82×10－6和116.4×10±26.42×10－6。体格发育正常的儿童发锌均值明显低于生长发育低下的儿童，分别是76.7×10－6±17.82×10－6和98．4×10-6±18．95×10-6。资料表明，年龄越小越易发生锌营养缺乏。     

NHCH=CHR自由基结构和稳定性ab initio研究

用ＵＨＦ／４－３１Ｇ基组，全构型优化，研究了ＮＨＣＨ＝ＣＨＲ（Ｒ＝Ｈ，ＢＨ２，ＣＮ，Ｆ，ＯＨ，ＮＨ２）６个氮自由基的构型和稳定化能△Ｅ，以ＮＨＣＨ＝ＣＨ２自由基为参考，它们的△Ｅ分别为０．００，－３４．９２，－８．３５，－０．９３，３３．０５，５０．８５ｋＪ．ｍｏｌ＾－１，说明供电子基团ＯＨ和ＮＨ２对氮自由基起稳定化作用，吸电子基团ＣＮ和ＢＨ２起去稳定化作用，而Ｆ对氮自由基的稳定性影响不大。     

自由基聚合的微型实验探索

采用微型实验进行自由基聚合是一种低成本、绿色实验,适用于教学实验,并有利于发展成设计型和综合型实验。文中,设计了自由基聚合的微型实验的方案,该方案可以充分揭示连锁聚合实施方法、工艺条件对实验所带来的差别,有利于学生对不同自由基聚合机理的掌握,起到事半功倍的效果。同时本文就微型自由基聚合实验如何体现设计型实验和综合型实验、揭示聚合工艺条件对聚合物的性能影响、自由基聚合动力学上的应用等方面的教学内容进行论述,通过实践教学环节,说明了微型实验的优势。     

丙烯与HBr/Br·发生自由基加成和取代反应的机理和竞争

含有α-H的烯烃可以与溴自由基发生自由基加成和自由基取代反应。本文以丙烯为例,论述了自由基加成和取代反应的机理和竞争关系,从而帮助读者更好地理解反应条件对优势反应及产物的影响。     

微量元素硒在防护自由基损伤中的作用

微量元素硒通过与谷胱甘肽过氧化酶的结合而发挥作用,清除自由基,阻断自由基引起的脂质过氧化反应,分解过氧化物,保护细胞膜,维持细胞功能的完整性。     

Etude du caractere nucleophile des radicaux lors de la reaction de transfert sur la liaison O-O des peracides

Peracids RC0₃H yield free radicals R' which react either with the peracid or with solvent giving the alcohol ROH and the hydrocarbon RH. The nucleophilic character of the free radicals was modified either by substitution of the carbon bearing the odd electron by inductive groups or by changing the free radical hybridation by the means of blocked structures such as cyclic or bicyclic free radicals. For each R, the measurement of the ratio ROH/RH establishes a reactivity scale for R with the peracid O-O bond. This reactivity does not depend on free radical stability but depends strongly on nucleophilic character. A primary free radical is less reactive than a secondary one, and is much less reactive than a tertiary one. A bridgehead free radical as the bicyclo[2.2.1]heptyle-1 does not react with the peracid. These results are interpreted to indicate a transition state with charge transfer (polar effect), the peracid being electrophilic and the free radical nucleophilic; PMO theory is discussed.     

Functionalized graphene quantum dots loaded with free radicals combined with liquid chromatography and tandem mass spectrometry to screen radical scavenging natural antioxidants from Licorice and Scutellariae

A novel screening method was developed for the detection and identification of radical scavenging natural antioxidants based on a free radical reaction combined with liquid chromatography with tandem mass spectrometry. Functionalized graphene quantum dots were prepared for loading free radicals in the complex screening system. The detection was performed with and without a preliminary exposure of the samples to specific free radicals on the functionalized graphene quantum dots, which can facilitate charge transfer between free radicals and antioxidants. The difference in chromatographic peak areas was used to identify potential antioxidants. This is a novel approach to simultaneously evaluate the antioxidant power of a component versus a free radical, and to identify it in a vegetal matrix. The structures of the antioxidants in the samples were identified using tandem mass spectrometry and comparison with standards. Fourteen compounds were found to possess potential antioxidant activity, and their free radical scavenging capacities were investigated. The order of scavenging capacity of 14 compounds was compared according to their free radical scavenging rate. 4′,5,6,7‐Tetrahydroxyflavone (radical scavenging rate: 0.05253 mL mg^?1 s^?1) showed the strongest capability for scavenging free radicals.     

SPIN TRAPPING OF FREE RADICALS PRODUCED FROM NITROSOAMINE CARCINOGENS

Abstract— Using the spin trap 5,5-dimethylpyrroline-1-oxide we have demonstrated that the nitrosoamine carcinogen, 1-nitrosopiperidine, upon incubation with rat liver microsomes and nuclei produces two trapped free radical species. One trapped species is the hydroxyl free radical whereas the other is a free radical of unknown structure of the carcinogen itself. Three other nitrosoamine carcinogens tested, including diethylnitrosoamine, dimethylnitrosoamine and 1-nitrosopyrroline yielded similar results with the exception that the trapped carcinogen radical differs dependent upon the compound used. Oxygen was required to produce the hydroxyl free radical but its presence decreased the yield of the carcinogen radical. Both cyanide and α-tocopherol acetate caused a decrease in the yield of the carcinogen free radical. Some heat-labile inhibitor(s) of radical production was/were present in the cytosol. The amount of radical produced was not proportional to the P₄₅₀ content.     

Effect of nano-SiO2 films on the evolution of proton-irradiated free radicals in Kapton

The free radical behaviors were investigated on the 170 keV proton-irradiated nano-SiO₂ deposited polyimide, using electron paramagnetic resonance (EPR) measurement. The results indicate that, compared with the case of nude polyimide, the population of free radicals is much higher and increase faster with the irradiation fluence and the nona-SiO₂ film thickness, but the g value of irradiated free radicals keeps at a constant of 2.0025. Theoretical analysis demonstrates that large quantities of the free radicals could be formed in the interface region, thus, the film coverage and thickness show significant influence on the population of the radicals in the interface. Due to the distribution heterogeneity of the free radical, the free radical evolution during the post-storage follows a sum of two exponential modes. The interface characteristic takes great effects during the evolution process. The mechanisms of the free radical formation and evolution are discussed detailedly in this paper.     

Free radical SH2′ reaction mechanism study by comparing free radical SH2′ reaction with free radical addition reaction

It is not clear whether the mechanism of the S_H2′ reaction of allyl chloride is concerted or stepwise. The relative rates of the competitive free radical addition to two different double bonds in (2-chloroallyl)-(2-choromethylallyl) ether have been determined. There are two competitive free radical addition reactions, one is free radical S_H2′ reaction and the other is free radical addition reaction. The mechanism of the S_H2′ reaction is discussed by comparing free radical S_H2′ reaction with free radical addition reaction.     

鸡足山耳蕨总黄酮的提取及抗氧化性研究

研究鸡足山耳蕨中总黄酮的提取及其抗氧化性.采用70％乙醇提取鸡足山耳蕨中总黄酮,用NaNO2Al(NO3)3-NaOH分光光度法测定黄酮含量,将提取液采用Fenton体系、普鲁士蓝法进行体外抗氧化活性研究,用硫代巴比妥酸(TBA)分光光度法研究其对羟自由基·OH引发DNA氧化损伤的抑制作用.结果表明样品中总黄酮含量为4.98％,回收率99.78％( RSD=1.06％,n=5).总黄酮浓度为90μg/mL时,对·OH的清除率可达36.2％;浓度为87.5μg/mL时,对羟自由基引发DNA损伤的抑制率可达93.0％.说明鸡足山蕨中总黄酮对羟自由基有较好的清除能力,对DNA氧化损伤有显著抑制作用.     

几种天然黄酮类化合物对二苯代苦味肼自由基的清除作用

采用循环伏安法、示差脉冲伏安法对四种天然黄酮类化合物清除二苯代苦味肼自由基（DPPH）的能力进行了探讨.研究表明：此法可直接观测样品对DPPH的清除作用,而且灵敏度高、准确可靠,是一种检测自由基及物质对其清除作用的有效方法.