Probing stereoselective inhibition of the acyl binding site of cholesterol esterase with four diastereomers of 2'-<Emphasis Type="Italic">N</Emphasis>-α-methylbenzylcarbamyl-1, 1'-bi-2-naphthol

Background  

Recently there has been increased interest in pancreatic cholesterol esterase due to correlation between enzymatic activity in vivo and absorption of dietary cholesterol. Cholesterol esterase plays a role in digestive lipid absorption in the upper intestinal tract, though its role in cholesterol absorption in particular is controversial. Serine lipases, acetylcholinesterase, butyrylcholinesterase, and cholesterol esterase belong to a large family of proteins called the α/β-hydrolase fold, and they share the same catalytic machinery as serine proteases in that they have an active site serine residue which, with a histidine and an aspartic or glutamic acid, forms a catalytic triad. The aim of this work is to study the stereoselectivity of the acyl chain binding site of the enzyme for four diastereomers of an inhibitor.     

Systematic Study of Ti‐Distribution in Titanosilicate *BEA Zeolites via Symmetry‐Adapted Enumeration

The high performance of titanosilicate zeolites in various industrial oxidation reactions is highly affected by the distribution of Ti atoms in their frameworks. Because of their structural complexity, previous theoretical studies mainly focus on the preferential location of single Ti atoms within the unit cells of titanosilicate zeolites. When multiple Ti atoms are required, conventional approaches consider only symmetrically related T sites to reduce the computation complexity. Such symmetry‐constrained approaches obviously overlooked many possible configurations. Herein, we conduct a systematic study on the distribution of two Ti atoms in the unit cell of titanosilicate zeolite *BEA . Different from conventional symmetry‐constrained approaches, we introduce two Ti atoms simultaneously without any constraint and adopt a symmetry‐adapted algorithm to enumerate all possible configurations for double‐Ti introduction. We generate a total of 273 distinct configurations and analyze the Ti‐distribution via Boltzmann statistics. We find that many of the configurations overlooked by conventional symmetry‐constrained approaches indeed exhibit more feasible energies, which may lead to different Ti‐distributions. Our study indicates the necessity of unconstrained introduction of Ti atoms when multiple‐Ti atoms are considered for calculations.     

杂多阴离子的有机金属化学(Ⅲ)——缺位Keggin阴离子PWO9-34的酯基锡杂多配合物的合成及性质

利用酯基锡与缺位Keggin结构杂多阴离子PW9O9-34反应,合成了6种新的杂多阴离子--有机金属配合物M9[(R'OOCCHR"CH2SnOH2)3(PW9O34)2]·xH2O(M=(CH3)4N+,K+;R'=CH3-,CH3CH2-;R"=H,CH3-),通过元素分析、IR光谱、紫外电子光谱、1H NMR、31P NMP、183w NMR和TGA-DSC热分析等测试手段对标题配合物进行了表征和性质研究,确定该系列配合物为A-β-PW9 型夹心配合物结构.     

萃取法研究Cu2+-dpx-PCA-体系配体间的芳环堆积作用及其配合物的组成

用萃取法测定Cu²⁺-dpx-PCA^-体系中的堆积百分数，其中dpx=2,2′-联吡啶胺(dpa)，2，2′-联吡啶甲烷(dpm)和2，2′-联吡啶酮(dpk); PCA^-=苯甲酸根(Bz^-), 2-苯乙酸根(PAc^-),3-苯丙酸根(PPr^-)和4-苯丁酸根(PBu^-)。结果表明：堆积百分数与羧酸根中亚甲基数有关，其顺序为Bz^---π电子协作效应的缘故。     

鳗鱼油的脂肪酸组成分析

鳗鱼加工下脚料（头、骨等）所得鱼油经甲酯化处理后，用GC和GC-MS进行了脂肪酸的组成分析，共签定出27个组分，它们占色谱峰总面积的97．9％。其主组分为油酸、棕榈酸、棕榈油酸，并含有廿碳五烯酸、廿二碳六烯酸，与鳗鱼肉中油的化学组成类似，具有开发利用的价值。     

铜(Ⅱ)-4-(喹啉-8′-甲基)-1,4,7,10-四氮杂环十三烷-11,13-二酮-α-氨基酸或5-取代邻菲罗啉两类三元配合物的稳定性研究

用 p H法在 (2 5.0± 0 .1 )℃ ,I=0 .1 mol· dm-3 KNO3 条件下 ,测定 Cu( ) - 4 - (喹啉 - 8′-甲基 ) - 1 ,4,7,1 0 -四氮杂环十三烷 - 1 1 ,1 3-二酮 -α-氨基酸或 5-取代邻菲罗啉两类三元配合物的稳定常数 ;研究了带甲基喹啉侧基大环多胺配体与 Cu( )离子的配位能力、配位方式 ;发现这两类三元体系配合物有特殊的稳定性 ;而且它们的稳定性与配体α-氨基酸及 5-取代邻菲罗啉酸碱强度之间的直线自由能关系的变化趋势相反 ;探讨了 Cu( )和 5-取代邻菲罗啉之间的 d- p反馈π键及其取代基 Hammett诱导效应的关系。     

药物控释载体醋酸酯淀粉的消化性能研究

采用生物体外(in-vitro)消化模型模拟人体消化道环境，对不同取代度的醋酸酯化木薯淀粉的消化速率进行了研究；用微生物酶对醋酸酯化木薯淀粉进行生物降解并测定各个样品的抗消化淀粉含量。结果表明醋酸酯化会增大淀粉颗粒的消化速率，但随取代度的提高消化速率呈下降趋势。同样随取代度的提高，醋酸酯化也会降低淀粉糊的消化速率。醋酸酯淀粉卡抗消化淀粉含量低于原淀粉，且取代度越高含量越低。醋酸酯化会破坏和抑制淀粉中抗消化淀粉的形成。     

3－苯氧甲基－6－（2，4－二氟苯基）－7H-1,2,4-三唑并[3,4-b][1,3,4]噻二嗪的合成与晶体结构研究

由苯氧乙酸出发，经多步反应，制得3-苯氧甲基－4－氨基－5－巯基－1，2， 4－三唑，它与2-氯－2'，4'－二氟苯乙酮进行环化反应，生成3-苯氧甲基－6－（ 2,4-二氟苯基）－7H-1,2,4-三唑并[3,4-b][1,3,4]噻二嗪，通过元素分析、红外 光谱、核磁共振氢谱与碳谱、质谱进行表征，并利用单晶X射线衍射法测定其结构 。晶体属单斜晶系、P2_(1/c)空间群，a = 1.339(3) nm, b = 1.4683(4) nm, c = 0.8606(2) nm, β = 108.49(2)°, Z = 4, F(000) = 736, R_1 = 0.0509。还 对均三唑并噻二唑两类稠杂环的晶体结构作了比较。     

溶剂热法制备Ag/TiO2纳米材料及其光催化性能

以乙醇为溶剂, 钛酸四丁酯为前驱体, 用溶剂热法制备了Ag表面修饰的负载型纳米二氧化钛光催化剂. 利用X射线衍射(XRD)、N₂吸附-脱附(BET)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)、紫外-可见(UV-Vis)光谱等技术对其进行了系统的表征, 以亚甲基蓝(MB)溶液的脱色降解为模型反应, 考察了不同Ag含量样品的光催化性能. 结果表明: 用溶剂热法制备的样品中TiO₂皆为锐钛矿相, 金属Ag颗粒沉积在TiO₂表面, 粒径为2 nm左右, 比表面积较溶胶凝胶法制备的样品大大增加, 最高可达151.44 m²·g^-1; UV-Vis光谱和光催化实验表明: Ag修饰使TiO₂对光的吸收能力大大增强, 吸收带边红移至可见光区, 亚甲基蓝在该复合材料上的光催化降解反应遵循一级反应动力学模型; 溶剂热法制备样品的光催化性能明显好于溶胶凝胶法制备的样品, 在紫外光和可见光下, Ag摩尔分数为5%的样品表现出最佳的光催化活性.     

配合物稳定性与配体酸碱强度之间的直线自由能关系 XIII. N-(间位取代苯基)氨基乙酸，邻菲啰啉(α,'α-联吡啶)与镍(II),钴(II)和锌(II)生成三元配合物的稳定性研究

The formation constants of ternary mixed ligand complex compounds (logK_(MAB~(MA)) formed from 1,10-phenanthroline or 2,2'-bipyridyl (A), N-(meta-substituted phenyl) glycines, (B, m-RphG, R=CH_3, H, CH_3O, Cl) with Nickel(Ⅱ), Cobalt(Ⅱ) and Zinc(Ⅱ) were determined by pH method at 25 ℃ in 30% (Volume) ethanol solution in presence of 0.1 mol·dm~(-3) NaClO_4 or 0.1 mol·dm~(-3) KNO_3. It was found that linear free energy relationships exist between the stability of ternary complex compounds and the base strengths of ligands in all six ternary systems investigated. The stability of the ternary complex compounds was discused in terms of ΔlogK_M values and HSAB theory. It was found that linear relationships also exist between ΔlogK_M and pK_2 in the Ni(II)-phen-m-RPhG ternary system.