DNA模板诱导针状CdS纳米粒子的形成

利用生物分子作为模板合成无机纳米粒子 ,可以精确地控制生成粒子的结构、大小、形状等 ,这方面的工作已经引起了研究者的广泛关注[1].目前 ,已经对许多生物分子作为无机纳米粒子合成模板剂的可行性进行了探索 .Ｍａｎｎ等[2 ]利用蛋白质作为模板合成ＣｄＳ纳米粒子 ;Ｗａｎｇ等[3]利用哺乳类眼睛晶状体管蛋白作为模板合成纳米尺寸的ＣｄＳ粒子 ;Ｂｒａｕｎ等[4 ]将寡聚核苷酸连接在两个金电极之间 ,用ＤＮＡ分子作为模板生长出长 1 2 μｍ、直径 1 0 0ｎｍ的银纳米线 ;Ｓｈｅｎｔｏｎ等[5 ]用烟草斑纹病毒的蛋白外壳作模板剂诱导生成无机 …     

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…     

DNA寡聚核苷酸链和免修饰纳米粒子体系的分析应用研究

DNA寡聚核苷酸链和免修饰纳米粒子体系越来越多地应用于分析化学中.其中,基于DNA寡聚核苷酸链和金纳米粒子(AuNPs)所构建的比色传感器引起了诸多研究兴趣.在这些体系中,DNA作为识别单元,不仅可以识别其互补链,而且可以识别一系列的目标物.金纳米粒子作为感应单元,具有依赖于粒子间距离的独特光学性质.依据这一原理,我们发展了一种简便的基于DNA和免修饰金纳米粒子检测Hg~(2+)的方法,主要利用单双链DNA与AuNPs间的不同作用和T-Hg~(2+)-T碱基配对理论,通过改变DNA双链中的T-T错配碱基数目,调控了传感器对Hg~(2+)检测范围.     

纳米银的电化学合成

纳米颗粒因具有量子尺寸效应、表面效应和宏观量子隧道效应等不同于晶态体材料和单个分子的固有特性 ,显示出体材料不具备的导电特性、光电特性、光催化能力及随粒径变化的吸收或发射光谱 ,已被用于各种发光与显示装置[1] .其制备的化学方法主要有溶胶 -凝胶法、微乳法、化学沉淀法和醇解法等 [2 ] .近年来 ,新发展出一种电化学合成纳米粒子的方法 ,如 Braun等 [3]利用 DNA模板电化学合成了银纳米线 ,Yu等[4 ] 用电化学合成了金纳米棒 ,Zhu等[5] 利用超声电化学合成了半导体 Pb Se纳米粒子 ,Amigo等 [6 ]用电化学方法合成了 Fe-Sr氧化…     

功能性CdS纳米荧光探针荧光增敏法测定人血清白蛋白

目前 ,以荧光分析法对蛋白质进行研究主要采用有机荧光探针[1～ 3 ] .与传统的有机染料 (如罗丹明 )探针相比 ,半导体纳米晶体探针的光强度要高 2 0倍 ,光稳定性要高 1 0 0倍 ,谱线宽度只是有机染料谱线宽度的 1 /3 [4 ] .将半导体纳米晶体作为探针用于测定生物分子 ,将大大提高分析的灵敏度和选择性 ,而目前其应用于生物染色、医疗诊断、DNA序列测定和免疫分析等方面的研究很少 [4 ,5] .本文合成了胶态纳米粒子 Cd S,并在其外表面修饰一层巯基乙酸 ,使其具有水溶性 ,并能与生物分子作用 ,从而可利用其外表面的功能性基团对人血清白蛋白进…     

基于纳米金胶标记DNA探针的电化学DNA传感器研究

以纳米金胶为标记物,将其标记于人工合成的5-端巯基修饰的寡聚核苷酸片段上,制成了具有电化学活性的金胶标记DNA电化学探针;在一定条件下,使其与固定在玻碳电极表面的靶序列进行杂交反应,利用ssDNA与其互补链杂交的高度序列选择性和极强的分子识别能力,以及纳米金胶的电化学活性,实现对特定序列DNA片段的电化学检测以及对DNA碱基突变的识别.     

功能化纳米金增强的DNA电化学检测和序列分析

用冠以大量二茂铁的纳米金微粒 /抗生蛋白链菌素结合物为标记物 ,将其标记于生物素修饰的寡聚核苷酸片段上 ,制成了具有电化学活性和纳米金放大作用的DNA电化学生物传感器 .首先采用巯基DNA和巯基烷烃混合自组装膜制备了金修饰电极 ,将探针DNA分子固定在了电极表面 ,运用杂交原则结合靶点分子在电极表面形成了双螺旋的DNA链 ,然后借助抗生蛋白链菌素和生物素之间的强亲和作用 ,引入了功能化的纳米金 .通过伏安法测定了修饰在纳米金上的二茂铁的氧化还原电流 ,可以识别和测定溶液中互补的靶点DNA ,17 mer靶点DNA的浓度在 0 .0 0 1～ 10nmol/L范围内有线性关系 ,检测限可达 0 .75× 10 -12 mol/L .     

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．     

基于金纳米粒子的QCM实时检测DNA错配的研究

利用石英晶体微天平（QCM）技术,用双硫醇分子作为连接剂,将金纳米粒子固定于金电极表面,以人类p53基因片断为DNA探针,研究了其在QCM金电极表面的固定、杂交和错配,重点探讨了金纳米粒子修饰的DNA错配碱基个数和错配位点对杂交的影响。在实验条件下,金纳米粒子在QCM金电极表面的修饰使其灵敏度得到了明显提高;而且,错配碱基个数和错配碱基位点的差异都对杂交产生了不同程度的影响。     

巯基修饰寡聚DNA包覆的CdS纳米粒子

用5'－端的1－C,2-C位之间磷酸根上修饰有巯基的寡聚胞嘧啶(oligoC10-SH)和矣鸟嘌呤(oligoG10-SH)作为包覆剂直接合成了CdS半导体纳米粒子。实验结果表明CdS的表面的寡聚DNA仍可进行正常的复性,并且复性后CdS的荧光发生了有利于DNA分子标识的显著增强。     

聚硼酸酯表面活性剂囊泡自发形成

通过直接引发聚合, 以偶氮二异丁腈为引发剂, 用N-羟甲基丙烯酰胺、硼酸三乙酯和N,N-二羟乙基十二烷基胺制备了聚硼酸酯(PMBE)表面活性剂, 用红外光谱、核磁共振谱和凝胶色谱对其结构进行了表征; 用透射电镜(TEM)研究了PMBE在纯水和0.1 mol/L NaCl水溶液中的自组装形态. 结果表明, PMBE在水和0.1 mol/L NaCl溶液中皆可自发形成聚合囊泡; 在水溶液中PMBE囊泡粒径约为20 nm, 而NaCl溶液中囊泡直径增大, 在150~250 nm之间, 分布较为均匀; 结合两亲性分子排列参数理论和一定的近似处理方法对PMBE聚合囊泡的形成机理进行了初步探讨.     

Supramolecular chirality of the hydrogen-bonded complex Langmuir-Blodgett film of achiral barbituric acid and melamine

Complex monolayers of barbituric acid and melamine were formed by spreading a chloroform solution of amphiphilic barbituric acid on the subphase of melamine solution. It was confirmed that the complex monolayer was formed through in situ complementary hydrogen bonding at the air-water interface. It was interesting to find that the complex LB films showed supramolecular chirality although both of the molecules were achiral, as verified by the circular dichroism spectral measurements. It was suggested that the pi-pi stacking of the neighboring barbituric acid and melamine group in a helical sense resulted in the chirality of the molecular assemblies. Due to the directionality of the hydrogen bonding, the BA-M film could form regular aligned nanofibers on the AFM images. Increasing the subphase temperature will lead to the decrease of CD intensity and the change of the morphologies. We suggested that the strength of the hydrogen bonding resulted in the difference.     

Inclusion of DNA into organic gelator fibers made of amphipathic molecules and its controlled release

When methyl 4,6-O-(p-nitrobenzylidene)-alpha-D-glucopyranoside (p-NO(2)Glu) was dissolved in water, p-NO(2)Glu molecules self-assembled to form a fiber (elemental fiber), and as a result, the solution became a partially transparent gel. When an equal (or more) amount of DNA was added to the gel, a white and crystalline gel was obtained. Energy-dispersive X-ray spectroscopy coupled with TEM and confocal microscopy suggested that DNA was included in the gel fibers made of p-NO(2)Glu molecules. The results imply that p-NO(2)Glu molecules are self-assembled to form an elemental fiber and these elemental fibers and DNA are twisted together to form higher hierarchic fibers. When the complexed gel made of plasmid DNA (pDNA) and p-NO(2)Glu was added to E. coli T7 S30 extract solution, the pDNA had less expression ability compared with naked one. When we added methyl-beta-cyclodextrin (MbetaCyD), the expression rate was recovered with increasing added amount of MbetaCyD. The present paper shows inclusion and controlled release of DNA from a novel supporting material of DNA and that technology could play an important role in the development of localized approaches to gene therapy.     

Quasielastic neutron scattering study of dynamics of CaCl2 aqueous solution confined in Vycor glass

Quasielastic neutron scattering was used to probe the diffusion of water molecules in 2.3 molal CaCl(2) solution confined in 100% hydrated Vycor glass in the temperature range of 220 to 260 K. We observed a gradual transition from the restricted diffusion regime at lower temperatures to unrestricted diffusion regime at higher temperatures. The diffusion parameters were compared with the data on pure water confined in Vycor available in the literature. We found that the effect of dissolved ions onto the diffusion dynamics of the water molecules in the solution was amplified by confinement by at least an order of magnitude compared to bulk form, even though the dissolved ions were found to have little effect on the spatial characteristics of the restricted diffusion process of water molecules. At 260 K, the local diffusion coefficient of water molecules in the H(2)O-CaCl(2) confined in Vycor was only 6% of the value reported for pure water confined in Vycor.     

Organization of beta-cyclodextrin under pure cholesterol, DMPC, or DMPG and mixed cholesterol/phospholipid monolayers

The complexation of beta-cyclodextrin with monolayers of cholesterol, DMPC, DMPG, and mixtures of those lipids has been studied using Brewster microscopy, PMIRRAS, and ab initio calculations. An oriented channel-like structure of beta-cyclodextrin, perpendicular to the air/water interface, was observed when some cholesterol molecules were present at the interface. This channel structure formation is the first step in the cholesterol dissolution in the subphase. With pure DMPC and DMPG monolayers, weaker, less organized complexes are formed, but they disappear almost completely at high surface pressure, and only a small amount of phospholipid is dissolved in the subphase.     

Mechanism underlying bioinertness of self-assembled monolayers of oligo(ethyleneglycol)-terminated alkanethiols on gold: protein adsorption, platelet adhesion, and surface forces

The mechanism underlying the bioinertness of the self-assembled monolayers of oligo(ethylene glycol)-terminated alkanethiol (OEG-SAM) was investigated with protein adsorption experiments, platelet adhesion tests, and surface force measurements with an atomic force microscope (AFM). In this work, we performed systematic analysis with SAMs having various terminal groups (-OEG, -OH, -COOH, -NH(2), and -CH(3)). The results of the protein adsorption experiment by the quartz crystal microbalance (QCM) method suggested that having one EG unit and the neutrality of total charges of the terminal groups are essential for protein-resistance. In particular, QCM with energy dissipation analyses indicated that proteins absorb onto the OEG-SAM via a very weak interaction compared with other SAMs. Contrary to the protein resistance, at least three EG units as well as the charge neutrality of the SAM are found to be required for anti-platelet adhesion. When the identical SAMs were formed on both AFM probe and substrate, our force measurements revealed that only the OEG-SAMs possessing more than two EG units showed strong repulsion in the range of 4 to 6 nm. In addition, we found that the SAMs with other terminal groups did not exhibit such repulsion. The repulsion between OEG-SAMs was always observed independent of solution conditions [NaCl concentration (between 0 and 1 M) and pH (between 3 and 11)] and was not observed in solution mixed with ethanol, which disrupts the three-dimensional network of the water molecules. We therefore concluded that the repulsion originated from structured interfacial water molecules. Considering the correlation between the above results, we propose that the layer of the structured interfacial water with a thickness of 2 to 3 nm (half of the range of the repulsion observed in the surface force measurements) plays an important role in deterring proteins and platelets from adsorption or adhesion.     

Effects of bridge ions, DNA species, and developing temperature on flat-lying DNA monolayers

Recently, we have successfully constructed flat-lying DNA monolayers on a mica surface (J. Phys. Chem. B 2006, 110, 10792-10798). In this work, the effects of various factors including bridge ions, DNA species, and developing temperature on the configuration of DNA monolayers have been investigated by atomic force microscopy (AFM) in detail. AFM results show that the species of bridge ions and developing temperature play a crucial role during the formation process. For example, the divalent cation Zn2+ resulted in many DNA chains stuck side by side in the monolayers due to the strong interactions between it and DNA's bases or the mica surface. Most DNA chain's conglutinations disappeared when the developing temperature was higher than 40 degrees C. Cd2+ and Ca2+ produced more compact DNA monolayers with some obvious aggregations, especially for the DNA monolayers constructed by using Ca2+ as the bridge ion. Co2+ produced well-ordered, flat-lying DNA monolayers similar to that of Mg2+. Furthermore, it was found that the flat-lying DNA monolayers could still form on a mica surface when plasmid DNA pBR 322 and linear DNA pBR 322/Pst I were used as the DNA source. Whereas, it was hard to form DNA monolayers on a (3-aminopropyl)triethoxysilane-mica surface because the strong interactions between DNA and substrate prevented the lateral movement of DNA molecules. These results suggested that the appropriate interactions between divalent cations and DNA or mica surface were important for the formation of flat-lying DNA monolayers. The obtained information is a necessary supplement to our previous studies on the formation kinetics of such monolayers and may be useful for practical application of the monolayers and further theoretical studies.     

Influence of Poly(ethylenimine) on the Monolayer of Oleic Acid at the Air/Water Interface

The effect of poly(ethylenimine) (PEI) dissolved in water on the surface pressure-area isotherm of oleic acid (OA) at the air/water interface was investigated. On a concentrated PEI solution, the isotherm of the OA monolayers exhibited a noticeable difference as a function of subphase pH. PEI caused the collapse pressure of the OA monolayer to increase up to 45 mN/m, due to a stronger acid-base-type interaction occurring between the amine group of the PEI and the carboxyl group of OA; on a pure water subphase, the collapse pressure was;28 mN/m. On the other hand, owing to a stronger OA-PEI interaction, the OA monolayers favored a liquid-expanded state more on the PEI-containing water subphase than on the pure water. From the QCM measurement, each OA molecule appeared to interact, on average, with 4.3-5.8 ethylenimine repeating units at basic pHs. We also found that OA multilayers could be assembled on a hydrophilic substrate by a Z-type Langmuir-Blodgett (LB) deposition in a PEI-containing subphase at basic pHs. The ATR-IR spectral data revealed that, in a Z-type LB film, the headgroup of OA was mostly present as carboxylate, interacting in an ionic state with the protonated amine groups of PEI. In acidic conditions, neither a Y-type nor a Z-type deposition was really accomplished. Nonetheless, the ATR-IR spectral data suggested that OA molecules should exist in a monomeric state in a LB film assembled at acidic pHs without PEI while they would form intermolecular hydrogen bridges and/or dimers in the presence of PEI. Copyright 2000 Academic Press.     

Atomic force microscopy of DNA at high humidity: irreversible conformational switching of supercoiled molecules

Three topologically different double-stranded DNA molecules of the same size (bps) have been imaged in air on mica using amplitude modulation atomic force microscopy (AM AFM) under controlled humidity conditions. At very high relative humidity (>90% RH), localized conformational changes of the DNA were observed, while at lower RH, the molecules remained immobile. The conformational changes occurred irreversibly and were driven principally by superhelical stress stored in the DNA molecules prior to binding to the mica surface. The binding mechanism of the DNA to the mica (surface equilibration versus kinetic trapping) modulated the extent of the conformational changes. In cases where DNA movement was observed, increased kinking of the DNA was seen at high humidity when more surface water was present. Additionally, DNA condensation behavior was also present in localized regions of the molecules. This study illustrates that changes in the tertiary structure of DNA can be induced during AFM imaging at high humidity on mica. We propose that AM AFM in high humidity will be a useful technique for probing DNA topology without some of the drawbacks of imaging under bulk solution.     

聚苯乙烯-聚(4-乙烯基吡啶)嵌段共聚物LB膜结构形态的研究

采用氯仿作为铺展溶剂,将嵌段共聚物聚苯乙烯-聚(4-乙烯基吡啶)(PS-b-P4VP)稀溶液铺展于空气与水界面上,利用Langmuir-Blodgett(LB)膜技术转移至固体基底.研究了不同的嵌段比、表面压和小分子1-芘丁酸(PBA)的加入对嵌段共聚物气液界面聚集组装的影响.研究发现随着亲水段(P4VP)的增加,聚集组装结构由纳米片状、带状转变成纳米条状、纳米点状结构.表面压对纯PS-b-P4VP聚集组装产生影响,表面压增大,组装体排列紧密;随着表面压的继续增大,单层聚集结构遭到破坏,发生堆叠.加入PBA小分子后,PBA与PS-b-P4VP形成氢键,形态发生明显变化,原来的片状结构转变为条状或点状结构.