利用侧链修饰寡聚DNA组装CdS有序纳米结构

由于 DNA分子具有特殊的结构和碱基配对特性 ,人们已经意识到利用 DNA分子将无机纳米粒子 (量子点 )组装成各种不同的有序纳米结构的可行性 [1～ 5] .如 Mirkin等 [6 ,7]利用端基修饰的寡聚 DNA将金纳米粒子组装成有序的六方堆积的层状结构 .Alivisatos等 [8]利用单链 DNA为模板 ,通过在 3′和5′端修饰巯基的互补 DNA将两个或三个金纳米粒子连接起来形成“人造分子”.本文中我们首次报道通过在侧链 ( 5′端 C1和 C2之间的磷酸根 )上修饰巯基的寡聚胞嘧啶 ( Oligo C10 - SH )和寡聚鸟嘌呤( Oligo G10 - SH)复性过程将 Cd S纳米…     

基于金纳米颗粒的裂分型适配体传感器检测三磷酸腺苷

构建了一种基于金纳米颗粒(Gold nanoparticles,AuNPs)的裂分型适配体荧光传感器,用于检测三磷酸腺苷(ATP).将ATP核酸适配体序列分裂为P1和P2两个片段,在P1的5′端修饰荧光基团羧基荧光素(FAM),3′端巯基化修饰的P2通过Au—S键以自组装的方式修饰在AuNPs表面.未加入ATP时,P1...     

半导体纳米粒子与金纳米粒子间荧光共振能量转移研究

采用水相法合成的CdTe半导体纳米粒子作为能量给体, 通过Schiff碱反应将单链DNA连接到表面. 采用柠檬酸钠还原氯金酸法制取的Au纳米粒子作为能量受体, 通过Au—S键将单链DNA连接到表面. 通过DNA链间的杂交, 构建了荧光共振能量转移体系(FRET). 测定了CdTe-DNA、 探针体系和探针体系+目标DNA的荧光强度. 结果表明, 探针体系的荧光强度最弱, 加入目标DNA后, 体系荧光增强, 表明该体系的构建是成功的.     

Lys-Lys诱导的金纳米粒子组装

尝试利用赖氨酸分子作为连接剂将金纳米粒子组装成有序的纳米结构．首先通 过赖氨酸的氨基与金纳米粒子的作用将其固定在粒子表面，然后通过氨基酸的缩合 将金纳米粒子连接成有序的纳米结构。透射电子显微镜观察表明形成的纳米粒子网 络结构中，相邻粒子之间的距离约为1．5m，与由两个赖氨酸缩合而成的二肽(Lys- Lys)长度相符．     

基于磁性纳米颗粒和金纳米粒子构建DNA电化学生物传感技术

本文构建了一种基于纳米粒子、茎环DNA和丝网印刷电极(SPCE)的电化学生物传感技术用于乳腺癌基因的快速、灵敏检测。该传感技术中,探针DNA的两端分别标记了巯基和生物素,巯基用于与金纳米粒子(AuNPs)作用,生物素用于与磁性纳米颗粒(MNPs)表面修饰的链酶亲和素作用以达到富集的目的,之后利用SPCE进行电化学检测。无目标DNA存在时,双标记DNA保持茎环结构,使得生物素分子很难和MNPs上的亲和素接触。一旦加入目标DNA,茎环结构打开,生物素得以与MNPs上的链霉亲和素发生特异性结合,形成的复合物(MNPs-DNA-AuNPs)通过磁性富集到SPCE表面,从而获得AuNPs的电化学信号。该DNA电化学生物传感对单碱基错配有良好的分辨能力,完全互补DNA的检出限为8.0×10-13 mol/L。     

基于DNA电化学发光传感器研究金纳米颗粒对量子点的电化学发光影响

纳米金颗粒具有高的消光系数和良好的表面等离子体共振特性, 其等离子体共振特性受纳米金颗粒的尺寸和周围环境等因素的影响. 本文基于半导体纳米晶电化学发光信号对金纳米颗粒的距离依赖性制备了DNA电化学发光传感器. 首先利用循环伏安法(CV)在玻碳电极(GCE)表面原位沉积金纳米颗粒(AuNPs), 巯基丙酸包裹的CdS量子点(QDs)与氨基修饰的双链DNA (dsDNA)通过酰胺键缩合, 形成量子点修饰的双链DNA(QDs-dsDNA). 最后将QDs-dsDNA 通过dsDNA 另一端的巯基组装到纳米金表面, 得到CdS QDs-DNA/AuNPs/GCE电化学发光传感器. 在优化电极表面QDs-dsDNA密度、金纳米颗粒沉积方法等实验条件的基础上, 对不同传感器的表面性质进行了表征, 如形貌和电化学阻抗等. 进一步通过控制纳米金和CdS QDs之间的DNA研究了纳米金对CdS QDs发光信号的影响作用. 结果显示DNA链的长度和类型对发光信号有着重要的影响. 最后将此传感器用于环境污染物的DNA损伤检测, 显示出很好的灵敏响应.     

纳米金颗粒增强信号的电化学生物传感器用于谷胱甘肽和半胱氨酸的检测

构建了一种高灵敏检测谷胱甘肽(GSH)和半胱氨酸(Cys)的新型电化学生物传感器. 先将富含T碱基的DNA1和DNA2探针分别修饰在金电极和纳米金颗粒(AuNPs)上, 再加入Hg²⁺, 通过形成T-Hg²⁺-T结构使AuNPs结合到金电极表面. 当加入GSH(或Cys)后, GSH(或Cys)可以竞争结合T-Hg²⁺-T结构中的Hg²⁺, 使AuNPs离开电极表面. 由于AuNPs上修饰的DNA探针能够静电吸附大量电活性物质六氨合钌(RuHex), 因此该过程可引起计时电量信号的显著变化, 据此实现了GSH(或Cys)的高灵敏检测. 该传感器的检出限达10 pmol/L, 比荧光法或比色法降低了2~3个数量级. 实验结果表明, 该传感器具有较好的选择性.     

基于金纳米颗粒信号放大效应电化学检测DNA聚合酶

基于金纳米颗粒(AuNPs)比表面积大、 尺寸小和能够承载大量DNA片段的特点, 建立了一种免标记、 简便、 快速检测DNA聚合酶Klenow fragment exo-(KF^-)的电化学方法. 首先将巯基化的DNA引物片段修饰在金电极上, 然后加入模板DNA链以及修饰有报告DNA链的金纳米颗粒(AuNPs-DNA), 模板DNA链能同时与DNA引物片段和修饰在AuNPs上的报告DNA链进行互补杂交形成"三明治"结构, 从而将AuNPs-DNA修饰在电极表面; 当加入电活性物质钌铵(RuHex)后, RuHex可通过静电吸附作用结合在DNA上. AuNPs上修饰的报告DNA链能够吸附大量RuHex, 导致电化学信号放大. 当加入脱氧核糖核苷三磷酸(dNTPs)以及KF^-聚合酶后, 引物片段发生延伸反应, 将与模板DNA链杂交的AuNPs-DNA竞争下来, 带走大量的RuHex, 使电信号降低, 从而实现对聚合酶的检测. 实验结果表明, 利用该方法可以检测到5 U/mL的KF^-.     

利用DNA三维纳米结构对量子点功能化的有序调控

利用DNA纳米技术构建了内部具有空穴的DNA纳米立方体结构,将量子点封装在其内部,可达到在量子点的特定位点修饰数量可控的不同DNA序列的目的,进而精准控制量子点的结合位点数量和空间取向.为了验证构建的结构表面可以功能化不同的DNA序列,且可控地连接在不同位点,继续通过DNA之间的杂交对此结构进行了不同尺寸金纳米粒子的组装.通过透射电子显微镜观察发现,在此方法下由DNA三维纳米结构与量子点组建的复合结构不仅能控制连接的金纳米粒子数量,还能控制组装后的几何构型.本文方法适于构建多结合位点与功能化的量子点探针,在生物医学方面有巨大的应用潜力.     

聚合物PVP保护的贵金属纳米结构材料电化学合成新方法

以不同聚合度的聚乙烯吡咯烷酮(PVP)作为金纳米团簇的稳定剂和形状控制剂,应用电化学还原方法制备尺寸可控的金纳米晶体.借助PVP聚合物的动态伸缩和卷曲特性将电化学还原得到的金纳米粒子前驱体组装成线状和环状的纳米粒子聚集体,再由不稳定前驱体粒子的定向聚集制备厚度为几十纳米的金纳米棱柱.并用分步电化学还原法合成核壳结构的金银纳米复合粒子.本文为制备不同形状和结构的贵金属纳米结构材料提供了一种可行的电化学合成新方法.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.