A novel and efficient ionic liquid supported synthesis of oligosaccharides

A novel and efficient ionic liquid supported synthesis of oligosaccharides with a general protocol of coupling and purification is described. The method represents an attractive alternative to the classical solid- and fluorous-phase synthesis strategies and combines the advantage of performing homogeneous chemistry on a relatively large scale while avoiding large excesses of reagents.     

α-松油烯-马来酸酐加成物的气相色谱分析

气相色谱法直接测定α－松油佛－马来酸酐加成物，不但免去了容量滴定法测定时必先分离共存马来酸酐的繁琐手续，而且方法简便、快速，能满足合成过程中跟踪分析的需要。     

Amphiphilic miktoarm star copolymers can self-assemble into micelle-like aggregates in nonselective solvents: a case study of polyoxometalate based miktoarm stars

It is well-known that amphiphilic star-shaped copolymers can self-assemble in selective solvents to form complicated micellar constructs as a synergistic result of both the topological constraints and relative volume fractions of the arms. Although the association phenomena of amphiphilic stars have been observed in nonselective solvents, both the structural detail and formation mechanism of these associates are not clear yet. Moreover, these experimental observations are controversial with respect to molecularly dispersed starlike copolymers in nonselective solvents as is popularly believed. To clarify these issues, we have synthesized a series of polyoxometalate-based polystyrene-poly(ethylene glycol)(PS-PEG) miktoarm star supramolecular copolymers(SEW-1–5) by coupling a Keggin-type polyoxometalate of K_4[α-SiW_(12)O_(40)] with 1,2,3-triazolium bridged block copolymers of-PS_n-b~+-PEG_mI~-(n=17, 26, 39, 57, 81; m=45) through ionic exchange reactions, respectively. TEM imaging,contact angle and ~1H NMR studies reveal that SEW-2–5 self-assemble in chloroform, THF, and toluene to create micellelike aggregates ranging from cylinder to sphere with a PS corona and a PEG core, while for SEW-1, reverse bilayers are captured with a PEG corona and a PS core. Among these aggregates, the Keggin clusters of [α-SiW_(12)O_(40)]~(4-) localize at the core-corona interfaces between PS and PEG. In terms of solvent quality, chloroform, THF, and toluene are only slightly poorer for PEG than that for PS with a relative order of chloroformTHFtoluene. These unexpected aggregates originate from the topological constraints of the chemically different arms of PS and PEG in the miktoarm stars, where the weak incompatibility between the PS and PEG arms is intensified appropriately. The presence of the reverse bilayered structures of SEW-1 is due to the magnified steric hindrance of the PEG45 arm with decreasing the molecular weight of the PS17 arm. However, to the best of our knowledge,these are the first examples clearly indicating that miktoarm star copolymers can self-assemble in common good solvents or slightly selective solvents to generate micellelike aggregates. This scenario is not only in sharp contrast to the intuitively considered behavior of unimolecular miktoarm stars in nonselective solvents, but also rather different from the conventional selfassembly behavior of amphiphilic star copolymers in selective solvents.     

稀土离子对大鼠肝细胞核脂质过氧化的影响

用光度法测定丙二醛 (MDA)研究不同浓度La3 +,Ce3 +,Pr3 +,Nd3 +,Eu3 +对大鼠肝细胞核脂质过氧化的影响。结果表明 :稀土离子在 1×10 - 4 ～ 1× 10 - 6mol·L- 1 浓度范围内能抑制振荡温育或H2 O2 引起的脂质过氧化 ,且与浓度正相关。但是对大鼠肝细胞核用稀土离子处理一定时间 ,稀土离子Eu3 +对脂质过氧化的抑制作用明显减弱 ,甚至会导致脂质过氧化加强     

负载型贵金属催化剂的硫中毒机理——载体的酸碱性与催化剂抗硫性能的关系

以H_2S为毒物,H_2-O_2反应为催化模型反应,制备并考察了一系列不同酸碱性的负载型钯催化剂。以NH_3和吡啶为探针分子,用程序升温脱附(TPD)或红外光谱法测定了催化剂的酸碱性。用交替脉冲微反色谱技术评价了催化剂的活性和耐硫中毒性,并对催化剂的耐硫性能和载体酸碱性进行关联和解释。在以上研究基础上,指出了提高催化剂抗硫性能的途径。     

流动注射分光光度法测定微量硫氰酸根

基于３，５－Ｂｒ２－ＰＡＤＡＰ硫氰酸根分别与重铬酸根，铈（ＩＶ）在硫酸介质中反应成不稳定的蓝色产物，建立了两种测定微量硫氰酸根的流动注射分光光度新方法，在前一方法中，硫氰酸根含量在０．８０～７．２０ｍｇ／Ｌ范围内可定量测定，检出限为０．２７ｍｇ／Ｌ在后一方法中，硫氰酸根含量在０．８０～６．４０ｍｇ／Ｌ范围内呈线性，检出限为０．３０ｍｇ／Ｌ。当进样体积为１００μＬ时，进样频率为６０次／ｈ，所建立的两     

（C_5H_5）_3Nd（THF）的晶体结构

报导了一种新型（Ｃ_５Ｈ_５）３Ｎｄ（ＴＨＦ）晶体结构，晶体属单斜晶系，Ｃ２／ｃ空间群，晶胞参数为ａ＝１２．８３９（７），ｂ＝１０．５２０（３），ｃ＝２６．５９９（９），β＝９８．５０°，Ｖ＝３５５３（３），Ｚ＝８，Ｄ_ｃ＝１．５４ｇ／ｃｍ￣３，Ｍ_ｒ＝４１１．６３，μ＝２９．２９ｃｍ（－１），Ｆ（０００）＝１６４０，最终偏离因子为Ｒ＝０．０６１，Ｒｗ＝０．０７３。新晶体结构在空间群、晶胞参数和Ｚ值上均明显不同于前面的报导，在Ｃｐ３Ｌｎ·ＴＨＦ系列化合物中，这是首次发现同一化合物可以用两种分子堆积方式结晶。     

金属置换碳酸酐酶及其生成动力学

本文报道了金属置换碳酸酐酶的活性研究。指出了离子半径的大小,配位构型的要求,热力学稳定性和配位体交换动力学是决定各种金属置换碳酸酐酶活性的重要因素。并用金属置换法测定了Ni(Ⅱ)与apo-CA形成金属酶的反应动力学速率常数。在25℃、pH7.47时,K_(fNi(Ⅱ)-CA)为14.01·mol~(-1)sec~(-1),较之于Zn(Ⅱ)-CA的速率常数小10~3倍。Cd(Ⅱ)-CA的生成动力学为一快反应,采用配位竞争法,在邻菲罗啉配位剂存在下,测得了Cd(Ⅱ)-CA生成动力学的条件速率常数在o-phen浓度为1.96和2.92×10~(-4)mol·1~(-1)时分别为137.1和114.61·mol~(-1)sec~(-1)。这一研究提示了镉对生物体的毒性作用的一个重要方面是使锌酶失活。而配位剂的存在大大降低了镉与脱辅基锌酶的反应动力学,这也是它们显示解毒功能所在。