脱氢枞酸及其衍生物生物活性的研究进展

脱氢枞酸是一种从松香中分离出来的具有三环二萜结构的树脂酸,具有广泛的生物活性,在医药、工业、农业等领域具有重要的用途。本文综述了脱氢枞酸衍生物在抑菌、抗病毒、K离子通道开启、抗肿瘤等生物活性方面的研究进展,展望了脱氢枞酸衍生物的研究和应用前景。     

Impact of thiourea concentration on the properties of sol–gel derived Zn(O,S) thin films and Cu(In,Ga)Se<Subscript>2</Subscript> solar cells

A novel approach based on sol–gel spin coating method to deposit Zn(O,S) thin film using thiourea(TU) as a sulfur source replacing CdS as buffer layer was developed and the influence of TU concentration on the properties of Zn(O,S) thin films and Cu(In,Ga)Se₂(CIGS) solar cells were investigated in this paper. It was found by X-ray diffraction and X-ray photoelectron spectroscopy that sol–gel derived Zn(O,S) thin films were amorphous and composed of ZnS, ZnO as well as Zn(OH)₂. The variation of the optical band gap as a function of the S/(S+O) ratio was determined by energy-dispersive spectroscopy and UV-VIS-NIR. The results indicated that the minimum value for band gap of approximate 3.72?eV was obtained when the S/(S+O)?=?0.44. Efficiency of up to 7.28% was achieved for a CIGS solar cell with Zn(O,S) buffer layer from 0.2M TU, which was attributed to the optimized conduction band offset (CBO) of +0.45?eV at the CIGS/Zn(O,S) interface.

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Zn(O,S) thin films prepared in sol–gel route was used to replace traditional CdS buffer layer deposited by chemical bath deposition method in Cu(In,Ga)Se₂ solar cells. The best efficiency was achieved for CIGS/Zn(O,S)/i-ZnO/ITO heterostructure solar cell with S/(S+O)?=?0.18, which was attributed to the optimized conduction band offset (CBO) of +0.45?eV at the CIGS/Zn(O,S) interface.

     

基于Topomer CoMFA方法的喹诺酮羧酸类衍生物的QSAR研究及分子设计

采用基于R基团搜索技术的Topomer Co MFA技术对一系列喹诺酮羧酸类衍生物进行三维定量构效(3D-QSAR)关系研究,所得模型结果的交叉验证相关系数(q2)为0.790,非交互验证系数(r2)为0.890,外部验证的复相关系数(r2pred)为0.878,研究结果表明该模型具有良好的稳定性和预测能力。采用Topomer search技术在ZINC数据库中进行虚拟筛选,筛选出6个Ra基团和3个Rb基团,进而设计出12个具有更高活性的新型喹诺酮羧酸类化合物。采用分子对接技术对药物与受体的作用机制进行了研究,结果显示,药物与蛋白酶的ASP 30、ASP 29和ASN 25位点作用明显,该QSAR的研究结果可为新药合成提供理论参考。     

金红石型氧化钛负载的铱在催化分解N_2O推进剂反应中的应用（英文）

氧化亚氮(N_2O)是一种性能独特优越的新型绿色推进剂,分解后可以生成高温富氧燃气,实现自增压式多种模式推进,是小卫星推进系统理想的推进剂选择,因而具有广阔的应用前景.在标准状态下,N_2O热分解反应活化能为250 k J/mol,致使其非催化热分解温度高达600 ℃,显然小卫星的能源系统无法满足,必须采取催化分解的手段,改变反应路径、降低反应活化能,使N_2O能够在较低的温度下分解.有关N_2O分解催化剂的报道很多,如纯相或复合氧化物、金属交换分子筛和负载贵金属等,但是这些催化剂仍然存在活性较低等问题,难以满足N_2O推进系统的应用需求.氧化钛是光催化和金催化常用的催化剂,经还原后能够形成氧缺陷,可以为涉氧反应提供电子,而N_2O分解会产生大量氧,氧脱附是其速率控制步骤,因而以氧化钛为载体,有望促进氧脱附及N_2O分解.与此同时,氧化铱具有较高的N_2O分解活性,而且与金红石型氧化钛晶格相似,相似的晶格参数可能会促进其在氧化钛表面的分散,进一步提高N_2O分解性能.基于此,本文以金红石氧化钛(r-TiO_2)为载体,采用匀相沉积沉淀法制备了不同载量的金红石氧化钛负载铱催化剂(Ir/r-TiO_2),并制备了锐钛矿型氧化钛、混合晶相P25和γ-Al_2O_3负载铱催化剂作为对比.通过活性测试我们发现,Ir/r-TiO_2催化剂显示了非常优异的N_2O分解活性,N_2O转化率明显高于参比催化剂,在250℃就能够开始分解,在300 ℃可以分解完全,而且当Ir含量降低到0.1%时,催化剂仍然保持与2 wt%Ir/γ-Al_2O_3相当的催化活性.随后我们采取多种表征手段对Ir/r-TiO_2的活性本质和N_2O分解机理进行了探究.首先利用BET、HAADF-STEM和XRD对催化剂的基本物性进行了测试,发现Ir/r-TiO_2具有较低的比表面积,但金属铱在金红石氧化钛表面表现出较高的分散度,平均粒径仅为1.25 nm.采用H-2-TPR和O 1s XPS考察了催化剂的电子特性和还原特性,发现Ir/r-TiO_2催化剂上高分散的Ir与氧的结合能较弱,易于还原,有助于N_2O的分解和生成氧的脱附.进一步采用原位N_2O-DRIFT对N_2O分解过程进行了研究,发现了桥式过氧物种,并据此提出了N_2O在Ir/r-TiO_2催化剂上的分解机理.     

Co-N/m-C高效催化空气下醇直接氧化成酯

酯类在有机合成中作为基础材料广泛地应用于精细化学品, 农用化学品, 药物等的生产中. 传统生产酯的方法需要用到羧酸, 酸酐, 酰卤或酮类, 并经过多步反应完成. 往往会造成原材料的浪费, 并伴随副产物的产生. 因此用醇代替酸或其衍生物与另一种醇反应直接氧化酯化合成相应的酯具有很大的经济意义. 目前已有基于贵金属(如钌, 钯和金)的将醇类直接氧化为酯类的催化剂的研究, 但是贵金属的价格及其有限的资源限制了其在实际生产中的应用. 从经济发展和环境保护的角度出发, 开发基于非贵金属的用于醇氧化酯化的催化剂有重要意义.近年来, 碳材料由于成本低? 稳定性高? 电化学性能优异的特点而广泛应用于材料? 化学催化和电化学催化等领域. 此外, 杂原子和金属的引入可以在一定程度上调节材料的组成, 电子结构和表面物理化学性质而进一步构建新的活性位点, 增强碳材料的催化性能. 另外, 由于多孔碳材料具有较大的比表面积和多样的孔结构, 作为催化剂载体比普通碳材料更优越, 使得底物更容易接触活性部位, 同时提高氧的传输能力. 然而, 活性钴物种因在热解过程中容易发生团聚而使原子催化效率降低. 因此设计和制备高分散且高效的催化剂对于实现醇氧化为酯有重要意义.钴基氮掺杂碳材料是一种有潜力的能将醇直接氧化到酯的经济, 高效, 环保的催化剂. 本文提出了一种方便, 快捷, 高效的醇直接氧化成酯的方法, 即利用直接热解大分子前驱体制备钴改性N掺杂介孔碳材料(Co-N/m-C), 用于醇直接氧化成酯反应中, 其中以900 oC下焙烧所制的催化剂活性最高. 该催化剂对于苯甲醇直接有氧氧化成苯甲酸甲酯反应的TOF值高达107.6 h?1, 远高于目前所报道的过渡金属基纳米催化剂的, 这得益于超分散钴物种与材料中吡啶氮之间的强配位作用及大的介孔比表面积. 对于不同结构的醇, 包括苄基醇, 烯丙基醇和杂环醇, 也能高收率地得到相应酯, 说明该催化剂具有普适性. 另外, Co-N/m-C-900催化剂经循环使用六次后没有显著的活性损失, 表明了该催化剂具有一定的稳定性.     

Preparation of CO2 responsive wormlike micelles and the effect of hydrogen bond on the strength of the network

We first prepared two types of CO₂-responsive wormlike micelles based on N-butyldiethanolamine–sodium oleate (BDEA–NaOA) and N,N-diethyl butylamine–sodium oleate (DEBA–NaOA), respectively. And then, we compared the two different systems to investigate the effect of hydrogen bond on the properties of wormlike systems. The results of the pH and conductivity variation show that tertiary amine groups on BDEA and DEBA were ionized to quaternary ammonium salts after bubbling of CO₂ into the systems, which work with OA^? to form wormlike micelles based on electrostatic interaction. The results of rheological measurements exhibit that the viscosity and viscoelastic of the BDEA–NaOA were obviously superior to DEBA–NaOA. The dramatically difference of the two kind of wormlike micelles was due to the strong intermolecular hydrogen bond between the BDEA and NaOA. This indicates that the hydrogen bond could show great effect on the properties of the wormlike micelles. Finally, a reasonable mechanism was proposed based on the molecular structure, micelles assembly, and the intermolecular interactions.     

Multicanonical parallel simulations of proteins with continuous potentials

The determination of the three‐dimensional (3D) structure of a protein or peptide is a very important research problem in biological and medical sciences. Anfinsen's experiments (Science 1973, 181, 223) on renaturation of denatured proteins have shown that the native 3D structure of a (small) protein at low (room) temperatures is uniquely determined by its amino acid sequence, which suggests that it might be possible to determine the 3D structure of a protein from its amino acid sequence by pure computations. As a step toward that goal, in this article we present a simple approach for parallelization of multicanonical Monte Carlo simulations of proteins with continuous potentials. Our method is based on the parallel calculation of the protein energy function. The algorithm is tested by simulated annealing and multicanonical simulations of two small peptides, and known results are reproduced accurately. An acceptable degree of parallelization can be achieved in the simulation of Protein L using up to 30 PCs. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1287–1296, 2001     

Au57Ag53(C≡CPh)40Br12: A Large Nanocluster with C1 Symmetry

The controlled synthesis and structure determination of a bimetallic nanocluster Au₅₇Ag₅₃(C≡CPh)₄₀Br₁₂ (Au₅₇Ag₅₃) is presented. The metal core has a four‐shell Au₂M₃@Au₃₄@Ag₅₁ @Au₂₀ (M=1/3 Au+2/3 Ag) architecture. In contrast to the previously reported large nanoclusters that have highly symmetric kernel structures, the metal atoms in Au₅₇Ag₅₃ are arranged in an irregular manner with C₁ symmetry. This cluster exhibits excellent thermal stability and is robust under oxidative or basic conditions. The silver precursors play a key role in dictating the structures of the nanoclusters, which suggests the importance of the counteranions used.