基于核酸特殊结构的分子识别及核酸相关纳米结构的设计应用

核酸为生命的最基本物质之一，是生物体遗传信息的携带者，在生长、遗传、变异等一系列重大生命现象中起决定性的作用。以核酸作为新药设计的靶分子，越来越受到人们的广泛重视。然而，不像其它靶分子如蛋白质、受体等具有特定的结构和功能，核酸结构在很多情况下是同源的，而且联系到很多人体正常的生理功能；能够与核酸结合的药物又往往不具有序列选择性，这就带来明显的毒副作用。因此，寻找和发现一些与疾病相关的核酸的特殊结构，并筛选对其有特异性结合能力的小分子，是以核酸为靶的药物研究的一个重要课题。 近年来，随着纳米科学技术的兴起，以核酸作为纳米体系的结构材料开始受到人们的广泛关注。作为一类特殊的线性高分子，核酸具有化学性质稳定，结构丰富且可控，良好的刚性和柔性，精确识别，高度生物相容性，合成方便等诸多优点，是一类优良的结构材料。目前核酸相关的纳米组装结构和器件研究还处于起步阶段，但是已经呈现出良好的发展前景。 本论文主要针对核酸特殊结构的分子识别及核酸相关功能纳米结构的设计这两方面展开了研究，全文由以下两大部分组成： 第一部分通过光谱学和生物化学等手段，研究了小分子对不同核酸结构的识别作用。借助于竞争平衡透析技术，发现一类恶嗪染料(oxazine dyes)能够与多种结构核酸结合。热变性及光谱实验结果表明，oxazine染料能够诱导杂合体三链核酸poly(rA):2poly(dT)的形成，并强烈地稳定其结构，其中以cresyl violet作用最强，是迄今发现的化合物中最强的。进一步研究发现，此类化合物以嵌插方式与杂合体三链核酸结合。RNase H酶切实验表明，杂合体三链核酸的形成能够强烈地抑制RNase H核酸酶的活性。研究了oxazine-170与三链核酸poly(dA):2poly(dT)及poly(rA):2poly(rU)的相互作用，发现oxazine-170能够强烈稳定三链DNA poly(dA):2poly(dT)的结构，而对相应双链DNA不具稳定作用；对三链RNA poly(rA):2poly(rU)及相应的双链RNA都有一定稳定作用，但作用不强。进一步研究发现，oxazine-170能够以两种结合方式与核酸结合：嵌插方式和外部静电堆积作用。研究了oxazine-170及cresyl violet与单链核酸的相互作用。研究发现oxazine-170能够序列特异性地与单链核酸poly(rA) 结合，CD光谱及AFM研究发现oxazine-170诱导poly(rA)形成新的二级结构。UV光谱、FL光谱及RLS研究发现poly(rA)促使oxazine 170形成H-aggregate，并以poly(rA)为模板自组装。而cresyl violet能够与单链核酸poly(rA)及poly(dA)结合，且采用不同的结合方式： cresyl violet能够与oxazine-170 类似地以poly(rA)为模板自组装；以嵌插方式与poly(dA)结合，并诱导其单链碱基堆积方式的改变。通过以上实验结果，我们进一步揭示了oxazine染料作为肿瘤细胞染色及光动力学治疗试剂的结构基础，对进一步设计、合成更加高效的抗肿瘤药物具有一定的指导意义。 第二部分中，我们尝试设计了几种基于核酸的纳米结构功能体系，并讨论了其相关应用。利用有机小分子coralyne能够诱导聚腺嘌呤序列反平行双链结构的形成，实现了一类新型的小分子诱导的纳米金组装结构。并以(dA)16功能化的金纳米粒子作为新型纳米探针，发展了一种简单的筛选单链核酸聚腺嘌呤序列结合分子的筛选方法。利用核酸限制性内切酶酶切位点回文序列的结构特点，设计了一种以DNA功能化的金纳米粒子组装体为酶切底物的比较通用的核酸限制性内切酶活力检测方法，并进一步用于甲基化酶活性检测及其抑制剂的筛选。基于单链DNA富胞嘧啶i-motif结构在不同pH值条件下的形成与解离，设计了一类质子驱动的DNA分子镊子，与基于链交换反应的DNA分子镊子相比，该体系更加简单，工作效率更高。随后，我们又通过合理设计，得到了两种分别能够结合与释放DNA和蛋白的分子镊子，为其应用做了一些探索。

染料脱色菌株筛选及染料脱色作用研究

染料废水成分复杂，色度高，是主要的环境污染源之一。应用微生物对染料废水脱色具有处理费用低和操作管理方便等优势，具有较好的发展前景。 本文采用筛选到一株短刺小克银汉霉(Cuuninghamella echinulata) KM3及一株红酵母(Rhodotorula sp.)YR-1分别对偶氮染料刚果红废水和酸性红废水进行了脱色研究，同时利用KM3及YR-1组成的复合菌种脱色体系对酸性红废水进行了脱色实验，为染料脱色真菌的应用奠定了基础。 KM3形成的菌丝球对多种染料具有较好脱色效果。KM3最适菌丝球形成条件：pH6-7、装液量90ml、孢子悬液浓度105个/ml (接种5ml)、摇床转速120rpm、培养温度30℃、培养时间72h；成球机理为凝聚型发育。KM3菌丝球对刚果红最佳脱色条件为：染料溶液初始pH值7.0，温度为33℃，摇床转速为120rpm。在刚果红50~200mg/l 浓度范围内， KM3菌丝球对刚果红吸附脱色动力学可用拟二级动力学方程描述。菌丝球对刚果红的吸附行为符合Langmuir和Freundlich 等温方程模型，Langmuir方程能更好的描述菌丝球对刚果红的吸附行为。丙酮对刚果红的解吸率最高，其解吸动力学过程符合二级动力学方程。将KM3应用在真菌生物滤床反应器中，在非灭菌和灭菌情况下接种孢子悬液后处理刚果红废水的过程中，均需长时间挂膜，处理效果一般。反应器中投加菌丝球后处理刚果红废水在3小时内达到92%以上的脱色效果。 YR-1对酸性红脱色机制属于降解脱色。YR-1对酸性红的最佳脱色培养条件为：初始pH 5.0、接种量5%、温度30℃；最佳碳源是葡萄糖，其次是蔗糖；最佳氮源是酵母膏或蛋白胨。在替换分批脱色实验和连续补料脱色实验中，脱色率一直保持在75%以上，显示YR-1在上述脱色体系中均具有良好适应性。 在三种复合菌种对酸性红的脱色体系中，体系Ⅲ（菌丝球与海藻酸钠固定化的酵母细胞混合培养）的脱色效果可达98%以上。对该体系而言，3种粒径固定化酵母小球（Ø1.1mm、1.8mm、3.1mm）中Ø1.8mm、3.1mm小球脱色率较为理想，而酵母细胞初始密度对脱色效果的影响不大。 KM3、YR-1分别具有处理刚果红废水和酸性红废水的应用前景，而KM3与YR-1联合应用对酸性红的脱色效果更好。

The synthesis and characterization of novel liquid crystalline, meso-tetra[4-(3,4,5-trialkoxybenzoate)phenyl]porphyrins

Five, novel, meso-tetra[4-(3,4,5-trialkoxybenzoate)phenyl]porphyrins and their metal complexes were synthesized and their molecular structures were confirmed by H-1 NMR, FTIR spectroscopy and elemental analysis. Mesomorphic studies using DSC, polarizing optical microscope and X-ray diffraction revealed that all compounds exhibited thermotropic columnar mesophases over a wide mesophase temperature range and low liquid crystalline-crystal line transition temperature. (c) 2007 Elsevier Ltd. All rights reserved

Highly efficient red electroluminescent polymers with dopant/host system and molecular dispersion feature: polyfluorene as the host and 2,1,3-benzothiadiazole derivatives as the red dopant

By selecting polyfluorene as the polymer host, choosing 2,1,3-benzothiadiazole derivative moieties as the red dopant units and covalently attaching 0.3 mol% of the dopant units to the side chain of the polymer host, we developed a novel series of red electroluminescent polymers of dopant/host system with molecular dispersion feature. Their EL spectra exhibited predominant red emission from the dopant units because of the energy transfer and charge trapping from the polymer backbone to the dopant units. The emission wavelength of the polymers could be tuned by modifying the chemical structures of the dopant units.

Gold nanoparticle-based surface enhanced Raman scattering spectroscopic assay for the detection of protein-protein interactions

In the present work, a sensitive spectroscopic assay based on surface-enhanced Raman spectroscopy (SERS) using gold nanoparticles as substrates was developed for the rapid detection protein-protein interactions. Detection is achieved by specific binding biotin-modification antibodies with protein-stabilized 30 nm gold nanoparticles, followed by the attachment of avidin-modification Raman-active dyes. As a proof-of-principle experiment, a well-known biomolecular recognition system, IgG with protein A, was chosen to establish this new spectroscopic assay. Highly selective recognition of IgG down to 1 ng/ml in solution has been demonstrated.

The synthesis and properties of meso-tetra(4-alkylamidophenyl)porphyrin liquid crystals and their Zn complexes

A series of novel, long-chain-substituted, porphyrin derivatives, meso-tetra (4-alkylamidophenyl) porphyrin ligands and their Zn complexes (alkyl = 8,10,12,14,16,18) were prepared by acylation of the amino groups of 5,10,15,20-tetra(4-aminophenyl)porphyrin by alkyl chloride. Mesomorphism was investigated by DSC, polarized optical microscopy (POM) and X-ray diffraction (XRD). Only ligands containing chains > 12 carbon atoms displayed liquid crystalline behaviour, which exhibited a high phase transition temperature and a broad mesophase temperature span, Zn complexes showed no liquid crystalline behaviour. Cyclic voltammetry, luminescence spectra and surface photovoltage spectroscopy revealed that covalent linking of an alkylamido group to the tetraphenylporphyrin molecule influences, significantly, the properties of the porphyrin macrocycle.

Simultaneous blue, green, and red emission from diblock copolymer micellar films: a new approach to white-light emission

White-light emission is achieved from a single layer of diblock copolymer micelles containing green- and red-light-emitting dyes in the separate micellar cores and blue-light-emitting polymer around their periphery, in which fluorescence resonance energy transfer between fluorophores is inhibited due to micelle isolation, resulting in simultaneous emission of these three species.

Harvesting Excitons Via Two Parallel Channels for Efficient White Organic LEDs with Nearly 100% Internal Quantum Efficiency: Fabrication and Emission-Mechanism Analysis

By incorporating two phosphorescent dyes, namely, iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,C-2']picolinate (Flrpic) for blue emission and bis(2-(9,9-diethyl-9H-fluoren-2-yl)-1-phenyl-1 H-benzoimidazol-N,C-3) iridium(acetylacetonate) ((fbi)(2)Ir(acac)) for orange emission, into a single-energy well-like emissive layer, an extremely high-efficiency white organic light-emitting diode (WOLED) with excellent color stability is demonstrated. This device can achieve a peak forward-viewing power efficiency of 42.5 lm W-1, corresponding to an external quantum efficiency (EQE) of 19.3% and a current efficiency of 52.8 cd A(-1). Systematic studies of the dopants, host and dopant-doped host films in terms of photophysical properties (including absorption, photoluminescence, and excitation spectra), transient photoluminescence, current density-voltage characteristics, and temperature-dependent electroluminescence spectra are subsequently performed, from which it is concluded that the emission natures of Flrpic and (fbi)(2)Ir(acac) are, respectively, host-guest energy transfer and a direct exciton formation process. These two parallel pathways serve to channel the overall excitons to both dopants, greatly reducing unfavorable energy losses.

Surface modification of poly(dimethylsiloxane) microchips using a double-chained cationic surfactant for efficiently resolving fluorescent dye adsorption

This paper described a double-chained cationic surfactant, didodecyldimethylammonium bromide (DDAB). for dynamic surface modification of poly(dimethylsiloxane) (PDMS) microchips to reduce the fluorescent dyes adsorption onto the microchannel. When DDAB with a high concentration was present as the dynamic modification reagent in the running and sample buffer, it not only reversed the direction of electroosmotic flow, but also efficiently suppressed fluorescent dyes pyronine Y (PY) or rhodamine 8 (RB) adsorption onto the chip surface. In addition, vesicles formed by DDAB in the buffer with higher surface charge density and electrophoretic mobility could provide wider migration window and potential for the separation of compounds with similar hydrophobicity. Factors affecting modification, such as pH and concentrations of the buffer, DDAB concentration in the buffer were investigated. Compared with commonly used single-chained cetyltrimethylammonium bromide, DDAB provided a better modification performance.

Highly efficient single-emitting-layer white organic light-emitting diodes with reduced efficiency roll-off

By codoping blue and orange phosphorescent dyes into a single host material, a highly efficient white organic light-emitting diode (WOLED) with Commission Internationale de L'Eclairage coordinates of (0.38, 0.43) at 12 V is demonstrated. Remarkably, this WOLED achieves reduced current efficiency roll-off, which slightly decreases from its maximum value of 37.3-31.0 cd/A at 1000 cd/m(2). The device operational mechanism is subsequently investigated in order to unveil the origin of the high performance.

Tuning the Energy Level of Organic Sensitizers for High-Performance Dye-Sensitized Solar Cells

Cost-effective organic sensitizers will play a pivotal role in the future large-scale production and application of dye-sensitized solar cells. Here we report two new organic D-pi-A dyes featuring electron-rich 3,4-ethylenedioxythiophene- and 2,2'-bis(3,4-ethylenedioxythiophene)-conjugated linkers, showing a remarkable red-shifting of photocurrent action spectra compared with their thiophene and bithiophene counterparts. On the basis of the 3-f{5'-[N,N-bis(9,9-dimethylfluorene-2-yl)phenyl]-2,2'-bis(3,4-ethylenedioxythiophene)-5-yl}2-cyanoacrylic acid dye, we have set a new efficiency record of 7.6% for solvent-free dye-sensitized solar cells based on metal-free organic sensitizers. Importantly, the cell exhibits an excellent stability, keeping over 92% of its initial efficiency after 1000 h accelerated tests under full sunlight soaking at 60 degrees C. This achievement will considerably encourage further design and exploration of metal-free organic dyes for higher performance dye-sensitized solar cells.

Dye-Sensitized Solar Cells Based on Organic Sensitizers with Different Conjugated Linkers: Furan, Bifuran, Thiophene, Bithiophene, Selenophene, and Biselenophene

Six organic dyes with different conjugated linkers such as furan, bifuran, thiophene, bithiophene, selenophene, and biselenophene have been prepared in combination with the dihexyloxy-substituted triphenylamine donor and the cyanoacrylic acid acceptor. In conjunction with an acetonitrile-based electrolyte and a solvent-free ionic liquid electrolyte, these dyes exhibit 6.88-7.77% and 6.39-7.00% efficiencies, respectively. We have demonstrated that furan and selenophene can be employed as building blocks of sensitizers in stable solar cells for the first time. We have also studied the influence of heteroatoms on photocurrents and photovoltages with the aid of quantum calculations and transient photoelectrical decay measurements. Temperature-dependent electrical impedance experiments have shown that a relatively low external quantum efficiency of the dye with biselenophene linker is not related to the charge collection yield in the case of an acetonitrile electrolyte.

A simple route to incorporate redox mediator into carbon nanotubes/Nafion composite film and its application to determine NADH at low potential

Through a new and simple ion-exchange route, two-electron redox mediator thionine has been deliberately incorporated into the carbon nanotubes (CNTs)/Nafion composite film due to the fact that there is strong interaction between any of two among the three materials (ion-exchange process between thionine and Nafion, strong adsorption of thionine by CNTs, and wrapping and solubilizing of CNTs with Nation). The good homogenization of electron conductor CNTs in the integrated films provides the possibility of three-dimensional electron conductive network. The resulting integrated films exhibited high and stable electrocatalytic activity toward NADH oxidation with the significant decrease of high overpotential, which responds more sensitively more than those modified by thioine or CNTs alone. Such high electrocatalytic activity facilitated the low potential determination of NADH (as low as -0.1 V), which eliminated the interferences from other easily oxidizable species. In a word, the immobilization approach is very simple, timesaving and effective, which could be extended to the immobilization of other cationic redox mediators into the CNTs/Nafion composite film. And these features may offer potential promise for the design of amperometric biosensors.

Molecular design on highly efficient white electroluminescence from a single-polymer system with simultaneous blue, green, and red emission

A highly efficient white electroluminescent polymer with simultaneous blue, green, and red emission is reported, developed using a dopant/host strategy by covalently attaching both a green- and a red-light-emitting dopant to the side chain of a blue-light-emitting polymer host (see figure). In a single-layer device a maximum luminance efficiency of 7.3 cd A(-1) with CIE coordinates of (0.31,0.32) is achieved.