关于DNA分子计算机的研究

DNA分子计算机是一种生物化学计算机,具有高度并行性、大容量、低能耗的特点。目前关于DNA分子计算机的研究主要是抽象的计算模型和原理性的试验。介绍了DNA分子的组成、置换DNA分子链中部分碱基序列的生物置换操作方法和DNA图灵机的结构,提出了DNA逻辑运算器,并应用活性DNA分子完成逻辑运算。     

用暗场电镜技术观察DNA分子的超螺旋结构

随着拓扑酶的发现和深入研究,人们越来越多地注意到DNA分子的超螺旋结构在DNA复制、RNA转录及其调控过程中的重要的生物学意义。固然,对小分子环状DNA分子,可以经凝胶电泳把超螺旋数不同的分子区分开来,然而核酸电镜技术却能给出更为直观、准确的超螺旋分子的图象,成为超螺旋分子研究的重要实验手段,而暗场核酸电镜技术又较明场技术显出更大的优越性。按常规方法小心提取大肠杆菌质粒DNA PBR_(322)并分别制备用于暗场和明场观察的DNA样品,在     

基于分子信标的异或门DNA自组装计算模型

随着DNA计算研究深入,运用布尔逻辑电路实现DNA计算机已经成为研究的热点。分子信标是近年来备受关注的一种新型DNA探针,它具有高度的特异性和灵敏度。以分子信标作为自组装单元设计出异或门DNA计算模型,是一种新的有效方法。和以往的DNA计算模型相比,该模型操作简单,可靠性高,可重复使用。     

DNA单分子的纳米定位切割与拾取研究

报道了一种对DNA单分子进行精细的纳米定位切割和拾取的技术。首先用分子梳技术将DNA拉直固定在经3-氨基丙基三乙氧基硅烷修饰的云母基底上，然后通过精细控制原子力显微镜针尖与DNA样品之间的作用力，实现了对DNA链的定位切割和拾取。这种方法不仅可制备应用于临床遗传诊断和致病基因的定位等多种的微小DNA探针．而且有望发展为一种基于纳米操纵技术的DNA有序化测序策略。     

基于分子结的分子电子器件电性能研究

介绍了分子电子学的发展背景,并通过电极、分子以及电极-分子接触界面的分子结技术,对电极-分子-电极结中的电子传递现象进行了解释。另外,结合STM和裂分结技术,探讨了分子结中分子电子的测试方法,并对基于分子结中的分子电子器件的库仑阻塞、Kondo效应以及动力学随机记忆等进行了讨论。     

超分子光化学分子器件的进展

本文详细介绍了超分子的分子设计、合成和对各组成成份的要求，综述了超分子光化学分子器件研究的进展。     

基于LiCl盐浓度梯度的固态纳米孔DNA分子检测

针对生物分子通过固态纳米孔的速度过快所引起的低时间分辨率问题,采用氯化锂(LiCl)盐溶液和盐浓度梯度相结合的方法来提高检测过程中信号的时间分辨率.通过在氮化硅薄膜上制备固态纳米孔,并在纳米孔两端施加LiCl盐浓度梯度进行DNA分子检测,发现DNA分子信号频率随LiCl盐浓度梯度的增加呈指数递增趋势,10倍浓度梯度下的...     

应用Fe~(3+)在裸云母表面制作DNA分子的AFM样品的方法

原子力显微镜(AFM)既是观测生物大分子的有力工具,也是生物单分子操纵的有力工具.脱氧核糖核酸分子(DNA)是记栽了生物信息的重要生命分子,同时也是在分子器件领域具有极大潜力的天然纳米材料.利用AFM对DNA分子观察和操纵时,制样是关键.云母具有原子级平整的表面可作为观测DNA分子时的基底,但由于其表面负电性而不能和DNA分子很好地结合,所以通常需要对云母进行表面修饰.本文给出一种通过加入适量三价铁离子溶液在裸云母表面制作DNA样品的方法,可取代传统的云母表面修饰.该制样方法既可应用到基于AFM技术的DNA分子的形貌观察,也可应用在基于AFM技术的对DNA的单分子操纵.     

分子器件

分子器件的主要研究内容包括：分子导线、分子开关、分子整流器、分子存储器、分子电路和分子计算机等。相关实验技术为：LB膜、自组装、有机分子束外延生长和扫描隧道显微镜等。     

分子尺寸器件与单分子器件

未来的计算机可以小到什么程度?迄今无人可以做详尽的回答。但毫无疑问,硅基集成电路由于光刻技术的限制和生产成本随尺寸变小作指数增长,将很快达到它的极限(最小线宽100nm)。目前国际上已提出未来的纳米电子器件的各种方案,其中最小的器件有可能由单个分子所构成。扼要讨论了当前最“热门”的分子尺寸电子器件以及将要进一步发展的单分子电子器件。其中具有电双稳性能的分子是最可期许的材料。初步的研究结果表明能得到构成逻辑门用的单分子开关、超高密度存贮器和单分子整流器等功能器件的原型。最后还讨论了分子电子学进一步发展的前景和问题。     

A label-free biosensor based on organic transistors by using the interaction of mercapto DNA and gold electrodes

Organic thin-film transistors (OTFTs) with Au electrodes were successfully used as transducers for label-free deoxyribonucleic acid (DNA) sensors. Single-strand DNA (ssDNA), perfectly-matched double-strand DNA (dsDNA) and mis-matched DNA were immobilized on the surface of the source/drain electrodes of three OTFT devices respectively. The ssDNA molecules with mercapto group (–SH) can be well immobilized on the surface of Au electrode by chemical bond between –SH and Au atom. According to the significant difference in channel current, which was attributed to the changed contact resistances by introducing different DNA molecules on Au electrode, ssDNA, matched-dsDNA and mismatched-dsDNA were differentiated successfully in the experiments. The results may provide a promising approach for detecting DNA specificity and hybridization with label-free.     

Modeling of the Electrical Conductivity of DNA

The authors have developed a PSpice model of the electrical behavior of DNA molecules for use in nanoelectronic circuit design. To describe the relationship between the current through DNA and the applied voltage we used published results of the direct measurements of electrical conduction through DNA molecules. The experimental dc current-voltage (-) curves show a nonlinear conduction mechanism as well as the existence of a temperature dependent semiconductive voltage gap. A weighted least-squares polynomial fit to the experimental data at one temperature, with fitted temperature dependent polynomial coefficient of the linear term, was used as a mathematical model of electrical behavior of DNA. An equivalent electrical circuit was created in PSpice in which DNA was modeled as a voltage-controlled current source described by the mathematical model that includes temperature dependence . PSpice simulations with this model generated - curves at other temperatures that were in excellent agreement with the corresponding experimental data (average deviation 5%). This is important because having models of DNA molecules in the form of equivalent electronic circuits would be useful in the design of nanoelectronic circuits and devices.     

Biofunctionalization of Vertically Aligned Diamond Nanowires

Vertically aligned diamond nanowires are biofunctionalized using aminophenyl linker molecules to bond nucleic acid molecules with a well‐defined nanometer‐sized spacing to the transducer. This novel DNA biosensor combines the outstanding electrochemical properties of diamond as a transducer with the controlled bonding of DNA molecules to the tips of nanowires by use of an electrochemical attachment scheme. Nucleic acid molecules are bonded in this way and dispersed to the transducer, giving rise to optimized hybridization kinetics of DNA. Negatively charged redox mediator molecules (Fe(CN)₆^3?/4?) are applied for DNA‐hybridization sensing. Voltammetric detection of DNA hybridization by differential pulse voltammetry is performed with respect to its sensitivity and reproducibility. On a sensor area of 0.03 cm², a detection limit of 2.0 pM is achieved. As for the chemical stability of the DNA bonding to the diamond nanowires, no degradation over 30 hybridization/denaturation cycles could be detected. By use of this dilute DNA arrangement, single‐base mismatch discrimination is achieved. Under the same conditions, smooth diamond modified with phenyl is not suitable for amperometric DNA sensing.     

Thin-core fiber-optic biosensor for DNA hybridization detection

A real-time label-free DNA biosensor based on thin-core fiber (TCF) interferometer is demonstrated experimentally. The proposed biosensor is constructed by splicing a TCF between two segments of single mode fibers (SMFs) and integrated into a microfluidic channel. By modifying the TCF surface with monolayer poly-l-lysine (PLL) and single-stranded deoxyribonucleic acid (ssDNA) probes, the target DNA molecules can be captured in the microfluidic channel. The transmission spectra of the biosensor are measured and theoretically analyzed under different biosensing reaction processes. The results show that the wavelength has a blue-shift with the process of the DNA hybridization. Due to the advantages of low cost, simple operation as well as good detection effect on DNA molecules hybridization, the proposed biosensor has great application prospects in the fields of gene sequencing, medical diagnosis, cancer detection and environmental engineering.     

A high-density conduction-based micro-DNA identification array fabricated with a CMOS compatible process

A high-density CMOS-compatible deoxyribonucleic acid (DNA) array fabricated with a modified metallization process is demonstrated. The array consists of silicon nitride isolation to confine the DNA sample to a specific cell area defined by silicon dioxide to achieve low crosstalk between neighboring cells. A prehybridization process together with a conductive enhancement method are also developed to improve the signal to noise ratio. Nine orders of magnitude difference in conductance is measured between array cells with matched and single-based mismatched DNA samples. The matching of DNA molecules can then be easily detected by a simple digital switching circuit.     

A label-free,organic transistor-based biosensor by introducing electric bias during DNA immobilization

We report an improved label-free DNA sensor based on pentacene organic thin-film transistors (OTFTs). OTFT with top-contact structure was first fabricated by using pentacene as the active layer. Different electric biases were introduced between the source and gate contacts of OTFT during the single-stranded DNA (ssDNA) immobilization process in order to improve the immobilization efficiency of DNA molecules on the pentacene substrate. Atomic force microscopy (AFM) images show the application of positive bias can significantly improve the amount of the immobilized ssDNA. The potentiostatic effect of bias can induce more ssDNA molecules onto the pentacene surface, which leads to the improvement of sensor sensitivity reflected by the electric signals of OTFTs. Furthermore, an optimized immobilization time of 30 min was obtained at a constant bias that exhibits the highest immobilization efficiency. With this design, the optimized process conditions (+50 V bias and an immobilization of 30 min) for the ssDNA immobilization on the pentacene film were also obtained. As a result, the introduction of bias during immobilizing ssDNA molecules has been proposed to improve the immobilized efficiency, which provides an effective path to enhance the sensitivity of OTFT-based DNA sensors.     

Integer Programming Problem Based on Plasmid DNA Computing Model

A DNA algorithm by operating on plasmids was presented to solve a special integer programming, a typical hard computing problem. The DNA algorithm employed double-stranded molecules to encode variables of 0-1 programming problem, the encoded DNA molecules were inserted into circular plasmids as foreign DNA molecules. Followed by, a series of enzymatic treatments to plasmids were performed in order to find feasible solutions to the given problem. The final optimum was obtained by applying founded feasible solutions to object function. Compared with other DNA algorithms of integer programming problem, the proposed algorithm is simple, error-resistant, above all, feasible. Our work clearly showed the distinct advantages of plasmid DNA computing model when solving integer related programming problem.     

多通道SPR影像传感器及其对DNA的特异性检测

SPR传感器的响应包括多种成份,除了待测分子与探针分子相互结合引起的响应(特异性响应)外,还有样液中其它成份及其浓度的变化、温度变化以及非待测分子与敏感膜的相互作用引起的响应(非特异性响应).后者的存在会严重影响SPR传感器的测量精度.本文提供了一种提高检测精度的方法,即采用多通道SPR影像传感器结构,通过不同通道之间的比较,提取出待测分子与探针分子之间相互作用所引起的响应,在真正意义上实现了对生物分子相互作用的实时、动态检测.通过对DNA的检测,证明这种方法对生物分子相互作用的特异性检测是行之有效的.