细胞色素C在SAM修饰电极上的电化学行为

应用循环伏安法研究了细胞色素c在2-氨基乙硫醇自组装膜修饰金电极上的电化学行为。结果表明，细胞色素c在2-氨基乙硫醇修饰的金电极上的电子传递过程为—扩散控制的可逆反应，2-氨基乙硫醇自组装膜可用作细胞色素c电子传递的有效促进剂。依据电化学石英晶体微天平和电化学交流阻抗谱的测量结果，讨论了单分子膜的组装过程及其对促进细胞色素c电子传递的作用机制。     

羟基取代双烷烃链苯磺酸盐水气界面单层膜的分子动力学模拟

采用分子动力学模拟方法考察2-羟基-3,5-烷基苯磺酸钠表面活性剂分子在水气界面形成单层膜的过程,通过体系各组分的密度分布分析单层膜的形态,采用径向分布函数和氢键分布考察含有羟基的极性基在界面处的吸附构型,并根据转动时间相关函数对双疏水链的吸附构型进行分析。结果表明:羟基的存在减弱了极性基之间的静电排斥作用,增加了分子的饱和吸附量;两条烷烃链具有不同的界面吸附构型,烷烃链间的叠加缠绕增强了溶剂对表面活性剂分子的疏水力作用。     

Logical computation using algorithmic self-assembly of DNA triple-crossover molecules

Recent work has demonstrated the self-assembly of designed periodic two-dimensional arrays composed of DNA tiles, in which the intermolecular contacts are directed by 'sticky' ends. In a mathematical context, aperiodic mosaics may be formed by the self-assembly of 'Wang' tiles, a process that emulates the operation of a Turing machine. Macroscopic self-assembly has been used to perform computations; there is also a logical equivalence between DNA sticky ends and Wang tile edges. This suggests that the self-assembly of DNA-based tiles could be used to perform DNA-based computation. Algorithmic aperiodic self-assembly requires greater fidelity than periodic self-assembly, because correct tiles must compete with partially correct tiles. Here we report a one-dimensional algorithmic self-assembly of DNA triple-crossover molecules that can be used to execute four steps of a logical (cumulative XOR) operation on a string of binary bits.     

三维DNA自组装在多维背包问题中的应用研究

利用DNA自组装执行计算的思想已从实验上被证明了其可行性．已有多种理论模型被提出用以解决各种NP问题．基于DNA Tile自组装模型理论在二维下的扩展,本文设计了可以实现这一算法的三维DNA Tile组装系统,提出了一种用于解决多维背包问题的三维DNA自组装模型．该模型可以非确定性的输出可行性解决方案．分析表明系统可以在线性组装步骤内完成计算,所需的Tile种类数与问题维数无关．为探索三维DNA自组装的计算能力进行了一次有意义的尝试．     

一种基于DNA自组装模型求解最大团问题的算法

基于tiles理论模型和已有DNA自组装模型,结合最大团问题给出基于DNA自组装模型的算法设计,得到具体设计初始分子、规则分子和检测分子所需的DAE块种类.在此基础上采用荧光标记和凝胶电泳生物操作提出了一种求解最大团问题算法.该算法设计tiles的种类为Θ(n2+|E|),其生物操作复杂性为Θ(1).此算法降低了实验的复杂度,而且保证了实验的易操作性和结果的准确性。     

自组装DNA计算研究难点与展望

随着DNA计算领域研究的深入,自装组DNA计算的研究成为了并行计算领域的研究热点,在本文中,作者主要分析讲述当前自组装DNA计算的几种结构形式：一维的、二维的以及三维的自组装DNA分子结构特点和发展现状,并且提出现在自组装DNA计算发展的难点以及今后的发展展望。随着多学科交叉融合力度的加大,自组装DNA计算将会成为生物信息学、应用数学、计算机仿真学、智能计算、纳米材料科学等多领域专家的重要研究方向。     

Stem-cell-triggered immunity through CLV3p-FLS2 signalling

Stem cells in the shoot apical meristem (SAM) of plants are the self-renewable reservoir for leaf, stem and flower organogenesis. In nature, disease-free plants can be regenerated from SAM despite infections elsewhere, which underlies a horticultural practice for decades. However, the molecular basis of the SAM immunity remains unclear. Here we show that the CLAVATA3 peptide (CLV3p), expressed and secreted from stem cells and functioning as a key regulator of stem-cell homeostasis in the SAM of Arabidopsis, can trigger immune signalling and pathogen resistance via the flagellin receptor kinase FLS2 (refs 5, 6). CLV3p-FLS2 signalling acts independently from the stem-cell signalling pathway mediated through CLV1 and CLV2 receptors, and is uncoupled from FLS2-mediated growth suppression. Endogenous CLV3p perception in the SAM by a pattern recognition receptor for bacterial flagellin, FLS2, breaks the previously defined self and non-self discrimination in innate immunity. The dual perception of CLV3p illustrates co-evolution of plant peptide and receptor kinase signalling for both development and immunity. The enhanced immunity in SAM or germ lines may represent a common strategy towards immortal fate in plants and animals.     

车辆悬架系统的自适应模糊控制(英文)

悬架是用来支持车身的系统,通过隔离道路干扰使得乘客感觉舒适、并确保车辆稳定.为此研究了全车模型悬架系统在下列几种控制方式下的性能:被动控制、半主动控制、自适应标准可加性模型(SAM)下的主动控制.全车模型可以为车辆悬架系统提供一些必要的性能参数,如车身偏移、车轮偏移和悬架偏斜.乘坐的舒适性和车辆的操控性决定了所需悬架系统的性能.乘坐的舒适性取决于车身偏移和乘客座位的偏移,而车辆的稳定由其他自由度(如俯仰和滚转)决定.半主动和主动悬架控制的设计通过MATLAB/SIMULINK加以实现,充分考虑了不规则的路面,并以此验证半主动控制和SAM主动控制的性能.实验结果表明,SAM主动控制能够改善乘坐的舒适性和车辆的操控性.     

Molecular logic computing model based on self-assembly of DNA nanoparticles

In this paper, a logic computing model was constructed using a DNA nanoparticle, combined with color change technology of DNA/Au nanoparticle conjugates, and DNA computing. Several important technologies are utilized in this molecular computing model: DNA self-assembly, DNA/Au nanoparticle conjugation, and the color change resulting from Au nanoparticle aggregation. The simple logic computing model was realized by a color change, resulting from changing of DNA self-assembly. Based on this computing model, a set of operations computing model was also established, by which a simple logic problem was solved. To enlarge the applications of this logic nanocomputing system, a molecular detection method was developed for H1N1 virus gene detection.     

基于DNA链置换反应的编码器逻辑运算模型研究

作为自组装DNA计算领域中一门新技术,DNA链置换反应在分子计算领域得到了广泛的应用.基于自组装DNA计算原理,设计了对应不同逻辑门的DNA分子电路.基于DNA链置换反应机理构建了编码器逻辑电路的分子计算模型.当输入DNA分子信号链时,将不同分子浓度比的DNA分子逻辑门电路混合,借助分子间的特异性杂交反应及分子间链置换反应,最终可输出信号链分子.Visual DSD仿真结果表明了本文设计的编码器逻辑计算模型的可行性与准确性.为拓展分子逻辑电路的应用做出有益的探索.     

A simulation study on the thermal and wetting behavior of alkane thiol SAM on gold (111) surface

Molecular dynamics simulations have been performed to investigate the structural,thermal and wetting properties of self-assembled monolayer(SAM) of alkane thiol on gold surface.The specific heat capacity of the gold SAM surface was found to linearly increase with the temperature in the range 100–300 K.It was found to drop down at 400 K and this decrease might be attributed to the disorder of the SAM chains.Hydration of gold SAM surface for two different terminal groups,namely methyl(hydrophobic),and hydroxy(hydrophilic) was studied at room temperature.The difference in their wetting behavior and the structure of their interfacial water were examined from the estimation of the z density profile,radial distribution function,hydrogen bonds and orientation of water dipoles in the interfacial region.The present simulation results suggest that the wetting behavior of the gold SAM surface can be modified by altering the terminal functional group of the SAM chains.     

优化甲硫氨酸补料策略提高重组毕赤酵母G12-CBS合成S-腺苷甲硫氨酸

重组毕赤酵母G12-CBS经代谢工程改造,可高效表达重组S-腺苷甲硫氨酸(SAM)合成酶,并弱化了SAM转化途径的关键酶β-胱硫醚合成酶,是一株优良的SAM高产菌。为了利用G12-CBS高效合成SAM,需对前体(甲硫氨酸)的补料策略进行优化。首先在摇瓶中考察了不同甲硫氨酸(L-Methionine,L-Met)添加量对于G12-CBS的影响,发现每24hL-Met补加量超过3mg/mL时,会影响重组菌生长和SAM合成。在15L发酵罐中优化L-Met的补料速率,当外源补料速率为0.4g/(L·h)时SAM产量最高,分别比补料速率为0.2g/(L·h)和0.6g/(L·h)时提高22.2%和31.8%,达到13.01g/L,比出发菌最高产量提高54%。代谢物及酶活测定的结果表明,较低的L-Met补料速率(0.2g/(L·h))导致前体供应不足而影响SAM合成,过高的补料速率(0.6g/(L·h))可能会抑制三羧酸循环,并且影响氮源的摄取和利用,从而导致菌体生长和产物合成受到抑制。     

新型量子点修饰金电极的制备及其在检测多巴胺中的应用

用3-巯基丙酸(MPA)包覆的碲化镉量子点(CdTe QDs)在金电极上进行自组装,制备了CdTe QDs修饰金电极(CdTe QDs/Au E)。利用循环伏安法研究此修饰电极的电化学行为,以[Fe(CN)6]3-/4-为探针,考察了CdTe QDs自组装膜修饰金电极的电化学性质。而且研究了多巴胺(DA)在此电极上的电化学行为,结果表明:DA在此修饰电极上可被电催化氧化。差分脉冲伏安(DPV)氧化峰电流与DA浓度在1.00×10-9～6.40×10-5mol/L范围内呈线性关系,检出限为3.30×10-10mol/L.     

高半胱氨酸SAM膜电极的制备及其电化学行为研究

研究了高半胱氨酸在金电极上形成单分子自组装膜的条件，并利用循环伏安法，交流阻抗谱研究了[Fe(CN)6]^3-/4-在高半胱氨酸SAM膜电极上于不同pH值溶液中的电化学行为。循环伏安结果表明，在pH大于高半胱氨酸等电点的溶液中，[Fe(CN)6]^3-/4-在膜电极上的循环伏安曲线峰电流明显降低，峰分离差增大，说明随pH值的增加，[Fe(CN)6]^3-/4-离子对在SAM膜电极上的可逆性变差；交流阻抗图谱显示，由于SAM膜电极表面带负电荷时，[Fe(CN)6]^3-/4-难以靠近电极表面，使其与电极表面的电子交换反应变得困难，在SAM膜电极上的电化学反应电阻Rct明显增加，并且随电解质溶液的pH增加而增加。     

Machinery for protein sorting and assembly in the mitochondrial outer membrane

Mitochondria contain translocases for the transport of precursor proteins across their outer and inner membranes. It has been assumed that the translocases also mediate the sorting of proteins to their submitochondrial destination. Here we show that the mitochondrial outer membrane contains a separate sorting and assembly machinery (SAM) that operates after the translocase of the outer membrane (TOM). Mas37 forms a constituent of the SAM complex. The central role of the SAM complex in the sorting and assembly pathway of outer membrane proteins explains the various pleiotropic functions that have been ascribed to Mas37 (refs 4, 11-15). These results suggest that the TOM complex, which can transport all kinds of mitochondrial precursor proteins, is not sufficient for the correct integration of outer membrane proteins with a complicated topology, and instead transfers precursor proteins to the SAM complex.     

Functionalizing hydrogen-bonded surface networks with self-assembled monolayers

One of the central challenges in nanotechnology is the development of flexible and efficient methods for creating ordered structures with nanometre precision over an extended length scale. Supramolecular self-assembly on surfaces offers attractive features in this regard: it is a 'bottom-up' approach and thus allows the simple and rapid creation of surface assemblies, which are readily tuned through the choice of molecular building blocks used and stabilized by hydrogen bonding, van der Waals interactions, pi-pi bonding or metal coordination between the blocks. Assemblies in the form of two-dimensional open networks are of particular interest for possible applications because well-defined pores can be used for the precise localization and confinement of guest entities such as molecules or clusters, which can add functionality to the supramolecular network. Another widely used method for producing surface structures involves self-assembled monolayers (SAMs), which have introduced unprecedented flexibility in our ability to tailor interfaces and generate patterned surfaces. But SAMs are part of a top-down technology that is limited in terms of the spatial resolution that can be achieved. We therefore rationalized that a particularly powerful fabrication platform might be realized by combining non-covalent self-assembly of porous networks and SAMs, with the former providing nanometre-scale precision and the latter allowing versatile functionalization. Here we show that the two strategies can indeed be combined to create integrated network-SAM hybrid systems that are sufficiently robust for further processing. We show that the supramolecular network and the SAM can both be deposited from solution, which should enable the widespread and flexible use of this combined fabrication method.     

A molecular cryptography model based on structures of DNA self-assembly

With the progress of DNA computing, DNA- based cryptography becomes an emerging interdisciplinary research field. In this paper, we present a novel DNA cryptography that takes advantage of DNA self assembled structure. Making use of the toehold strands recognition and strand displacement, the bit-wise exclusive-or （XOR） operation is carried out to fulfill the information encryption and decryption in the form of a one-time-pad. The security of this system mainly comes from the physical isolation and specificity of DNA molecules. The system is con- structed by using complex DNA self-assembly, in which technique of fluorescent detection is utilized to implement the signal processing. In the proposed DNA cryptography, the XOR operation at each bit is carried out individually, thus the encryption and decryption process could be con- ducted in a massive, parallel way. This work may dem- onstrate that DNA cryptography has the great potential applications in the field of inRwmation security.     

DNA addition using linear self-assembly

This paper presents a DNA algorithm which adds two nonnegative binary integers using self-assembly in constant steps. The approach has the benefit of greater experimental simplicity when compared with previous DNA addition algorithms. For the addition of two binary n-bit integers, O（n） is different from DNA strands and only O（1） biochemical experimental procedures are required.     

毛细力驱动自组装定位模型

毛细力驱动自组装的定位是利用微元件及基片表面之间的毛细力作用实现的。为了研究微元件及组装区的形状对自组装定位的影响,在分析毛细力驱动自组装机理的基础上,利用能量法建立了毛细力驱动自组装系统的定位解析模型,预测了不同形状微元件的自组装结果,并对一些不合理的组装设计进行了修正。结果表明:通过计算自组装表面能量可以预测组装结果,并设计合理的粘合区形状。     

Self-assembly of micro parts on normal glass substrate

Fluidic self-assembly is an approach by which micro parts less than one millimeter in size can be driven by the capillary force of a certain adhesive liquid and be fixed onto the desired sites on some substrates. Normal glass with the composition of Na2SiO3CaSiO34SiO2 has been widely used in fluidic microelectromechanical systems (MEMS) and bio-MEMS devices. We investigate the MEMS self-assembly experiment on normal glass substrate. The results of scanning electron microscopy (SEM) show that micro-parts of 400 μm400 μm squares can be precisely assembled in the expected area of the normal glass substrate.