分子马达定向运动的合作机制

分子马达是当前生物学和物理学的前沿课题,其定向运动的动力学机制一直是科学家关注的焦点之一.生物体内的分子马达一般是很多个一起协同工作.相互作用与合作在分子马达集体行为中起了很大作用.本文概述了分子马达合作运动的现象和机制.为进一步阐述合作的意义,本文详细讨论了分子马达必须依靠合作才能实现定向输运的两种情况.第一种,分子马达通过合作,在过阻尼条件下克服不停闪烁的棘齿势,实现了定向运动.第二种,分子马达通过合作,可以将一个方向上输入的驱动能量转化到垂直方向上做功,并产生定向输运.     

高灵敏度离子分子的吸收光谱

介绍了光外差-磁旋转-速度调制吸收光谱技术对离子分子的研究,该技术综合了光外差光谱技术、磁旋转光谱技术和速度调制光谱技术三者的特点,形成可以对离子分子高灵敏度测量的光谱技术.该技术不仅保留了速度调制光谱技术对离子分子选择性探测的特点,避免了来自中性分子光谱线的干扰,同时利用光外差光谱技术降低来自光源的幅度涨落噪声,消除放电过程的干扰,再结合磁旋转光谱技术可以对顺磁性分子进行选择性测量以及进一步提高测量信噪比.介绍了光外差-磁旋转-速度调制光谱技术的基本原理、实验方案以及对N2+,CO+,H2O+等离子分子的测量研究结果.     

分子马达模型综述

对国内外分子马达的研究现状进行综述,以作直线运动的肌动蛋白和肌球蛋白为例,对其运动特点做描述,介绍三类分子马达的结构、功能及其性质,重点概述肌球蛋白的理论模型,展望分子马达的发展前景和应用.     

液晶聚合物分子排列调控的研究进展

液晶的应用不仅仅局限于电视或电脑,具有光响应性的液晶在许多领域都存在应用,如平板显示、光学领域、光驱动设备以及许多正在发展的微科技领域. 液晶作为一种中间相的物质,既表现出了液体的流动性,又具有晶态的分子规整排列的性质. 液晶软物质材料具有许多有趣的性质,如自组装性质;长程有序的流动性;分子协同作用;双折射性质和物理性质（光、力、和电）的各向异性;外场诱导的表面分子取向;以及液晶弹性体的刺激响应性形变. 文中综述了具有不同液晶分子取向排列的液晶聚合物的刺激响应性形变,着重介绍了光取向技术诱导液晶分子取向的液晶聚合物的刺激响应性形变行为,并展望了未来液晶材料的设计在微流体和微型机器人领域的潜在应用.     

光响应型主客体超分子聚合物

通过主客体非共价键作用将光响应基团引入超分子聚合物体系中可以获得光响应型超分子聚合物,此类聚合物在自愈合体系、聚集诱导发光、光控组装等领域具有重要应用。综述了近期基于冠醚、环糊精、杯芳烃、柱芳烃和葫芦脲为主体的光响应超分子聚合物的合成与性质,并对此类主客体超分子聚合物的发展前景进行了展望。     

分子马达模型综述

介绍三类马达酶的结构,功能和生命体内分子马达的研究状况,并详细介绍几类典型分子马达的理论模型,同时展望了分子马达的发展前景和应用。     

分子大小的马达

美国康奈尔大学的科学家利用更改了的大肠杆菌,创造了只有一粒分子大小的马达,可以在动物或植物的身体内移动,进行不同的医药功能.康奈尔大学的科学家是将一种称ATP的酵素,和一个经过改造的分子,变成一个小型马达,可以每秒钟旋转三至四次,持续的运行四十分钟.科学家希望,将这种新科技发展成为可以携带药物的马达,放在身体内运行,在恰当的时间和地方,将精确的药物数量,放进有病的细胞.     

Mn3Sn薄膜的磁光特性研究

采用超高真空分子束外延方法制备了Mn_3Sn(0002)取向薄膜.利用旋转磁光法测量了在膜面内不同方向施加磁场时的磁光克尔角,获得其最大磁光克尔角为20 mdeg.通过计算拟合,Mn_3Sn薄膜具有单轴单向磁各向异性,磁各向异性能常数(K_1)=3.75×10~3 J/m~3.通过对比Mn薄膜的实验数据,认为反铁磁构型的Mn与弱铁磁性的Mn_3Sn之间的界面磁耦合导致单轴单向磁各向异性,Mn的杂散磁矩对Mn_3Sn样品的磁光克尔角有贡献.     

基于分子马达的活细胞内微粒逃离势阱的运动概率

用Ｆｏｋｋｅｒ－Ｐｌａｎｃｋ方程研究了在活细胞内作拟布郎运动的微粒在分子马达驱动下跳离势阱的运动概率,进而得到ＡＴＰ分子的水解反应概率、马达蛋白分子的反应概率以及确定与活细胞内微粒膜连接的马达蛋白分子数和ＡＴＰ分子数的统计表达式。     

纳米机器——分子马达的研究现状及前景

本文介绍了分子马达的研究现状,并对它的研究前景进行了展望,更充分地说明了研究分子马达的机制对我们的重要性。     

Molecular machines: nanomotor rotates microscale objects

Nanomachines of the future will require molecular-scale motors that can perform work and collectively induce controlled motion of much larger objects. We have designed a synthetic, light-driven molecular motor that is embedded in a liquid-crystal film and can rotate objects placed on the film that exceed the size of the motor molecule by a factor of 10,000. The changes in shape of the motor during the rotary steps cause a remarkable rotational reorganization of the liquid-crystal film and its surface relief, which ultimately causes the rotation of submillimetre-sized particles on the film.     

Unidirectional rotary motion in a molecular system.

The conversion of energy into controlled motion plays an important role in both man-made devices and biological systems. The principles of operation of conventional motors are well established, but the molecular processes used by 'biological motors' such as muscle fibres, flagella and cilia to convert chemical energy into co-ordinated movement remain poorly understood. Although 'brownian ratchets' are known to permit thermally activated motion in one direction only, the concept of channelling random thermal energy into controlled motion has not yet been extended to the molecular level. Here we describe a molecule that uses chemical energy to activate and bias a thermally induced isomerization reaction, and thereby achieve unidirectional intramolecular rotary motion. The motion consists of a 120 degrees rotation around a single bond connecting a three-bladed subunit to the bulky remainder of the molecule, and unidirectional motion is achieved by reversibly introducing a tether between the two units to energetically favour one of the two possible rotation directions. Although our system does not achieve continuous and fast rotation, the design principles that we have used may prove relevant for a better understanding of biological and synthetic molecular motors producing unidirectional rotary motion.     

Unidirectional molecular motor on a gold surface

Molecules capable of mimicking the function of a wide range of mechanical devices have been fabricated, with motors that can induce mechanical movement attracting particular attention. Such molecular motors convert light or chemical energy into directional rotary or linear motion, and are usually prepared and operated in solution. But if they are to be used as nanomachines that can do useful work, it seems essential to construct systems that can function on a surface, like a recently reported linear artificial muscle. Surface-mounted rotors have been realized and limited directionality in their motion predicted. Here we demonstrate that a light-driven molecular motor capable of repetitive unidirectional rotation can be mounted on the surface of gold nanoparticles. The motor design uses a chiral helical alkene with an upper half that serves as a propeller and is connected through a carbon-carbon double bond (the rotation axis) to a lower half that serves as a stator. The stator carries two thiol-functionalized 'legs', which then bind the entire motor molecule to a gold surface. NMR spectroscopy reveals that two photo-induced cis-trans isomerizations of the central double bond, each followed by a thermal helix inversion to prevent reverse rotation, induce a full and unidirectional 360 degrees rotation of the propeller with respect to the surface-mounted lower half of the system.     

Light-driven monodirectional molecular rotor.

Attempts to fabricate mechanical devices on the molecular level have yielded analogues of rotors, gears, switches, shuttles, turnstiles and ratchets. Molecular motors, however, have not yet been made, even though they are common in biological systems. Rotary motion as such has been induced in interlocked systems and directly visualized for single molecules, but the controlled conversion of energy into unidirectional rotary motion has remained difficult to achieve. Here we report repetitive, monodirectional rotation around a central carbon-carbon double bond in a chiral, helical alkene, with each 360 degrees rotation involving four discrete isomerization steps activated by ultraviolet light or a change in the temperature of the system. We find that axial chirality and the presence of two chiral centres are essential for the observed monodirectional behaviour of the molecular motor. Two light-induced cis-trans isomerizations are each associated with a 180 degrees rotation around the carbon-carbon double bond and are each followed by thermally controlled helicity inversions, which effectively block reverse rotation and thus ensure that the four individual steps add up to one full rotation in one direction only. As the energy barriers of the helicity inversion steps can be adjusted by structural modifications, chiral alkenes based on our system may find use as basic components for 'molecular machinery' driven by light.     

分子马达运动机制的基本观点及力-化学耦合

从物理学角度讨论了分子马达定向运动机制的基本观点，介绍了用Fokker-Plank方程求解几率流的一般思想，以及分子马达力学和化学过程可能的耦合方式。     

Molecular motors

Life implies movement. Most forms of movement in the living world are powered by tiny protein machines known as molecular motors. Among the best known are motors that use sophisticated intramolecular amplification mechanisms to take nanometre steps along protein tracks in the cytoplasm. These motors transport a wide variety of cargo, power cell locomotion, drive cell division and, when combined in large ensembles, allow organisms to move. Motor defects can lead to severe diseases or may even be lethal. Basic principles of motor design and mechanism have now been derived, and an understanding of their complex cellular roles is emerging.     

机器人操作手末端夹持器轨迹生成的旋量方法

依据从基坐标系到任一坐标系的旋转变换可以通过绕给定轴的一次等效旋转来实现的原理,提出用等效角位移矢量来描述机器人的姿态,并进而提出用姿态旋量及其Plucker线坐标来描述机器人的位姿。依据三维欧氏空间中的有向直线与三维对偶空间中的点的对应关系,在对偶空间中对姿态旋量所对应的点进行插补规划,提出一种机器人连续运动轨迹规划的新方法。文末算例说明了上述原理和推导的正确性。     

分子元素与功能核酸分子

 介绍了"分子元素"概念。论述了核酸适体的筛选及其作为大分子药物的应用价值,概述了人工碱基的合成及进展;探讨了脱氧核酶的作用原理,分析了分子信标、分子马达在生物传感、生物合成、生物药物研究等方面的应用前景,展望了核酸分子研究领域的前景及面临的挑战。     

球形机器人准静态学分析及其路径规划方法

针对现有球形机器人在动力学分析及控制系统设计时遇到的计算量大、实时性差的难点,提出将机器人的转向和向前驱动运动分开独立执行的设计原则.根据球体滚动中的实际情况,利用转速矢量的投影关系,建立了机器人的两输入、五输出的准静态学运动方程,当要求转速不高的情况下,可以对球形机器人进行基于运动学的控制.提出了一种在运动解耦方式下的点对点直线插补式路径规划方法,这种方法可以逐点逼近任意要求的轨迹,具有一定实际工程应用价值.