甲基丙烯酸三苯墓甲酯和甲基丙烯酸酯类的共聚物在溶液中的螺旋诱导和解旋作用

甲基丙烯酸三苯墓甲酯和甲基丙烯酸酯类的共聚物在溶液中的螺旋诱导和解旋作用陈传福，刘卫宏，陈永明，任长玉，习复（中国科学院化学研究所北京１０００８０）关键词甲基丙烯酸三苯基甲酯，甲基丙烯酸甲酯，光学活性，螺旋诱导，解旋在手性阴离子复合引发剂存在下，甲基...     

Electrochemical Oxidation of Quercetin

The mechanism of electrochemical oxidation of quercetin on a glassy carbon electrode has been studied using cyclic, differential pulse and square‐wave voltammetry at different pH. It proceeds in a cascade mechanism, related with the two catechol hydroxyl groups and the other three hydroxyl groups which all present electroactivity, and the oxidation is pH dependent. Quercetin also adsorbs strongly on the electrode surface; and the final oxidation product is not electroactive and blocks the electrode surface. The oxidation of the catechol 3′,4′‐dihydroxyl electron‐donating groups, occurs first, at very low positive potentials, and is a two electron two proton reversible reaction. The hydroxyl group oxidized next was shown to undergo an irreversible oxidation reaction, and this hydroxyl group can form a intermolecular hydrogen bond with the neighboring oxygen. The other two hydroxyl groups also have an electron donating effect and their oxidation is reversible.     

Tasumatrols P – T,Five New Taxoids from Taxus sumatrana

The phytochemical investigation of the more polar fractions from the leaves and twigs of Taxus sumatrana (Taxaceae) afforded five new taxane diterpene esters, tasumatrols P–T ( 1 – 5 ) possessing an 11(15→1),11(10→9)‐diabeotaxane skeleton. Compounds 1, 4 , and 5 contain an α‐hydroxy group at C(14), while 3 has no OH group at either C(13) or C(14). Compound 2 is a natural 4,5‐acetonide derivative, while 4 has an unusual spiro‐connected 2‐hydroxy‐2‐phenyl‐1,3‐dioxolane ring. Ten known taxoids, were also isolated in the course of the chromatographic fractionation. Five additional new O‐acetyl derivatives 3a, 4a, 4b, 5a , and 5b were prepared from the taxanes 3 – 5 . The structures of all new compounds were established on the basis of their spectroscopic analyses. Compound 1 showed mild cytotoxic activity against human Hela and Daoy tumor cells.     

新型含吡啶基的不对称膦酸酯衍生物的合成与生物活性

通过2-氯-5-氯甲基吡啶与亚磷酸酯的Michaelis-Becker反应合成得到10个新型含吡啶基的不对称膦酸酯衍生物, 并对环状亚磷酸酯与2-氯-5-氯甲基吡啶反应的立体化学进行了研究, 结果表明: 不对称环状亚磷酸酯的电子效应和立体效应对反应的立体化学有着重要影响. 初步的生物活性结果表明, 该类化合物不具有杀虫活性, 但显现出较好的杀菌活性.     

含聚醚间隔链的扩链脲改性环氧树脂/双氰双胺固化体系性能研究

合成了一系列含不同分子量聚环氧丙烷 (PPG)柔性间隔链的扩链脲 ,系统考察了扩链脲改性环氧树脂E 5 1/双氰双胺 (dicy)固化体系的固化反应活性、动态力学行为、冲击性能和断裂面形态结构 ,并对体系的冲击性能、形态结构与动态力学行为之间的关系进行了探讨 .结果表明 ,改性体系固化反应活性明显提高 ,固化反应表观活化能降低 ,固化反应峰顶温度从 190℃降低至 14 0℃ ,固化反应的表观活化能由 14 5 5kJ/mol降至 70～ 80kJ mol;改性体系冲击强度明显提高 ,其中所含PPG柔性链分子量为 10 0 0的扩链脲改性的E 5 1/dicy体系冲击强度较未改性的E 5 1/dicy体系提高了 8倍 ,其冲击试样断裂面的形态具有明显的韧性断裂特征 ,微观两相网络结构的存在导致了改性体系冲击强度显著提高     

基于可见吸收信号的乳酸脱氢酶光纤传感器

报道一种测定乳酸脱氢酶活力的基于可见吸收信号的光纤生物传感器，在该传感体系中，通过辅酶Ｉ的氧化还原对（ＮＡＤ＾＋／ＮＡＤＨ）将乳酸脱氢酶和心肌黄酶催化的两个脱氢过阳以耦合，第一个脱氢过程对分析对象进行了化学识别，第二个脱氢过程引起可见吸收信号的变化，该传感器对０～４００Ｕ／Ｌ的乳酸脱氢酶有线性响应关系，检测下限为４８ＵＬ，该传感器已用于人体血清中乳酸脱氢酶活力的测定。     

Transfer activity coefficient of the proton in water-pyridine mixtures. A comparison of some extrathermodynamic assumptions

Various water-pyridine mixtures have been selected in order to compare several of the most popular extrathermodynamic assumptions involved in the determination of the transfer activity coefficient of the proton, _t(H⁺). Two techniques have been utilized for this purpose: voltammetry [study of the ferrocene, ferricyanide, or thallium(1) systems] and potentiometry at equilibrium (emf measurements of various galvanic cells, including liquid junctions and hydrogen electrode or silver electrode as a test electrode). The assumptions have been classified into various groups [e.g., _t(Z^p+)=_t(Z^q+) or _t(X^–)=_t(Y⁺)], and the values of _t(H⁺) have been experimentally determined in each case. The results vary depending upon the basic assumption (several pH units); less important differences (e.g., 0.5 pH unit) occur within a given group, and this may be assigned to the nature of the reference species chosen. A simple model of solvation has been also examined; the application of the law of mass action to the corresponding equilibrium provides results close to the _t(X^–) =_t(Y⁺)type of assumptions which ultimately leads to most self-consistent results.     

Antibacterial activity of methylated chitosan and chitooligomer derivatives: Synthesis and structure activity relationships

The purpose of this study was to synthesize series of methylated chitosaccharide derivatives, possessing various degree of methylation, and to determine their structure activity relationship (SAR) with regard to their antibacterial effect against Staphylococcus aureus. Chitosan polymer and chitooligomers were used as starting materials and were methylated by reaction with methyl iodide. Depending on the reaction conditions the degree of N-quaternization ranged from 0% to 74%, with varying degree of N,N-dimethylation, N-monomethylation and O-methylation. More selective N-quaternization could be obtained with protection group strategy. At pH 5.5 the chitosaccharide polymers and their methylated derivatives were active against S. aureus with minimal inhibitory concentration (MIC) ranging from 16 to 512 μg/mL. At pH 7.2 the non-quaternized derivatives were inactive but their highly N-quaternized derivatives showed MIC as low as 8 μg/mL. The chitooligomers, as well as their derivatives, were inactive at both pH’s. The SAR studies revealed that N-quaternization was mainly responsible for the antibacterial effects at pH 7.2, whereas it did not contribute to the antibacterial activity under acidic conditions.     

铈改性NaZSM-5分子筛担载Pd催化剂上CO氧化性能研究

以浸渍法制备了一系列添加CeO2的Pd-Ce/NaZSM-5负载型催化剂．以C0氧化为 模型反应，考察了反应温度、Ce含量、预还原、空速及水蒸气等对C0氧化性能的影 响，并利用XIlD和朋等手段对催化剂体相及表面结构进行了表征．结果表明：加入 CeO2作助剂可明显提高催化剂的活性，且催化转化率随着反应温度及Ce含量的增加 而增加；随着空速的增加而降低；催化剂对水蒸气不敏感，在水蒸气存在的条件下 反应可连续进行720h以上保持C0完全转化；H2预还原作用使催化剂活性有所提高． XRD测试结果表明，催化剂中Pd组分处于高分散状态，Ceob的引入促进了N物种在 NaZSM—5载体上的分散．表面XPS分析证实催化剂表面Pd物种处于较高的氧化状态 ，且CeO2与Pd物种间存在协同作用．Pd的高分散及其与CeO2的相互作用是催化剂具 有高活性的关键．     

Antibacterial activities of polystyrene-block-poly(4-vinyl pyridine) and poly(styrene-random-4-vinyl pyridine)

Styrene was polymerized in the presence of benzoyl peroxide (BPO) and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) to yield polystyrene-TEMPO (PS-TEMPO) macroinitiator. The PS-TEMPO macroinitiator with different molecular weight was reacted with 4-vinyl pyridine (4-VP) to synthesize polystyrene-block-poly(4-vinyl pyridine) (PS-b-PVP), which was then quaternized with n-octyl iodide. Antibacterial activity of the quaternized copolymers was assessed against a gram negative bacterium (Pseudomonas aeruginosa) and a gram positive one (Staphylococcus aureus) by using the shake flask test method, and the results were compared with those of poly(styrene-random-4-vinyl pyridine) (P(ST-r--VP)). The quaternized copolymers inhibited greatly the growth of the bacteria, and PS-b-PVP was more active than P(ST-r-VP), which was ascribed to the fact that the content of quaternized 4-VP units on the surface of the particles of the former copolymer was higher than that corresponding to the latter one.