Motor proteins at work for nanotechnology

The biological cell is equipped with a variety of molecular machines that perform complex mechanical tasks such as cell division or intracellular transport. One can envision employing these biological motors in artificial environments. We review the progress that has been made in using motor proteins for powering or manipulating nanoscale components. In particular, kinesin and myosin biomotors that move along linear biofilaments have been widely explored as active components. Currently realized applications are merely proof-of-principle demonstrations. Yet, the sheer availability of an entire ready-to-use toolbox of nanosized biological motors is a great opportunity that calls for exploration.     

The way things move: looking under the hood of molecular motor proteins

The microtubule-based kinesin motors and actin-based myosin motors generate motions associated with intracellular trafficking, cell division, and muscle contraction. Early studies suggested that these molecular motors work by very different mechanisms. Recently, however, it has become clear that kinesin and myosin share a common core structure and convert energy from adenosine triphosphate into protein motion using a similar conformational change strategy. Many different types of mechanical amplifiers have evolved that operate in conjunction with the conserved core. This modular design has given rise to a remarkable diversity of kinesin and myosin motors whose motile properties are optimized for performing distinct biological functions.     

Directional switching of the kinesin Cin8 through motor coupling

Kinesin motor proteins are thought to move exclusively in either one or the other direction along microtubules. Proteins of the kinesin-5 family are tetrameric microtubule cross-linking motors important for cell division and differentiation in various organisms. Kinesin-5 motors are considered to be plus-end-directed. However, here we found that purified kinesin-5 Cin8 from budding yeast could behave as a bidirectional kinesin. On individual microtubules, single Cin8 motors were minus-end-directed motors, whereas they switched to plus-end-directed motility when working in a team of motors sliding antiparallel microtubules apart. This kinesin can thus change directionality of movement depending on whether it acts alone or in an ensemble.     

电源电压对农用电动机性能影响的剖析

本文通过测试与分析,偏重电源电压对农用电动机性能影响的研究,从而为农电部门及农用电动机用户的节能降损工作提供寻求措施的依据。     

南上座泵站最优补偿功率因数分析

从提高泵站运行效率的观点 ,结合宝鸡峡南上座泵站机组的实际资料 ,对该泵站异步电动机组进行补偿分析 ,找出了功率因数与无功补偿容量、投资变化率及投资回收年限之间的关系。结果表明 ,在南上座泵站 ,异步电动机组功率因数补偿到 0 .94时最为经济。     

步进电机的虚拟仪器控制系统

基于虚拟仪器技术的步进电机控制系统,采用虚拟仪器替代传统仪器、测试软件替代硬件电路的方式,实现了步进电机的正、反转控制.借助于LabVIEW图形化编程软件,按照控制系统的要求,组建了步进电机控制系统,并给出了控制过程的虚拟前面板及程序框图.虚拟仪器在步进电机控制系统的开发应用,提高了步进电机控制过程的自动化和智能化水平,为步进电机在控制领域的应用,提供了一种简便易行的方法.     

Powering an inorganic nanodevice with a biomolecular motor

Biomolecular motors such as F1-adenosine triphosphate synthase (F1-ATPase) and myosin are similar in size, and they generate forces compatible with currently producible nanoengineered structures. We have engineered individual biomolecular motors and nanoscale inorganic systems, and we describe their integration in a hybrid nanomechanical device powered by a biomolecular motor. The device consisted of three components: an engineered substrate, an F1-ATPase biomolecular motor, and fabricated nanopropellers. Rotation of the nanopropeller was initiated with 2 mM adenosine triphosphate and inhibited by sodium azide.     

分马力三绕组单相电容异步电动机的设计

论证了三绕组单相异步电动机较两绕组电机的优点，运用合成电流法编制了分马力多绕组单相异步电动机的电磁计算程序，并具体分析了Y接三绕组单相电容异步电动机。经过大量的分析与计算，提出了设计原则，确定了定子各绕组参数的配置和最佳设计区域，并得到了实验验证。分析与计算结果表明，三绕组单相电动机相对两绕组电机在运行力能指标上有较大提高，基本与同机座号三相异步电动机相当．因而有很好的生产应用前景。     

国产电驱离心压缩机组在天然气管道的应用

近年来,电驱离心压缩机组在天然气管道压气站中被大量采用,国产电驱机组虽然起步较晚,但发展较快。回顾了国产电驱离心压缩机组在天然气管道的应用现状及发展概况,系统归纳了机组主要单元的组合方式、成套方式、电动机、变频调速装置、控制系统的主要技术特点。通过运行数据分析、典型故障分析及与进口机组对比分析等方法,归纳总结了国产电驱机组相对进口压缩机组的优势与不足,并在设计、运行、管理及售后方面提出建议。从20 MW以上国产电驱机组研制、国产电驱机组推广、变频高速异步电动机应用、集成式压缩机的研制以及磁浮轴承在国产分体式电驱机组上的研制与应用等方面进行了展望,认为国产电驱机组必将成为未来中国天然气管道输送的核心动力装备,也更加安全、环保、可靠、经济。     

Engineering cooperativity in biomotor-protein assemblies

A biosynthetic approach was developed to control and probe cooperativity in multiunit biomotor assemblies by linking molecular motors to artificial protein scaffolds. This approach provides precise control over spatial and elastic coupling between motors. Cooperative interactions between monomeric kinesin-1 motors attached to protein scaffolds enhance hydrolysis activity and microtubule gliding velocity. However, these interactions are not influenced by changes in the elastic properties of the scaffold, distinguishing multimotor transport from that powered by unorganized monomeric motors. These results highlight the role of supramolecular architecture in determining mechanisms of collective transport.     

农用电动机节能途径的研究

从理论上分析了农用是动机经济运行的可行性，提出了在农村中电动机进行节能的技术措施，并以实例说明了其节电效果。     

转差闭环调速系统动态设计方法研究

转差频率控制是异步电动机变频调速系统转矩控制的重要方法，本文从讨论转差频率控制原理及转差闭环高速系统的控制结构出发，研究了异步电动机数学模型的工程简化及电压型变频高速系统转差闭环控制的动态设计问题，提出了类似直汉高速系统动态设计的工程设计方法，经仿真研究证明了该方法的可行性。     

生物技术在百合上的应用

对生物技术在百合 (Liliumspp .)上的应用研究进展进行了综述 .生物技术在百合上的应用主要包括以下几个方面 :利用植物离体培养技术成功建立了百合快速繁殖体系和脱毒苗生产技术程序 ;利用胚胎拯救技术克服了百合杂交前后障碍获得百合新品种 ;蛋白质分子标记、DNA分子标记在百合的初步应用 ;通过农杆菌介导法、基因枪法、电激法等进行了百合的遗传转化 ,并通过基因枪法成功地获得了百合转基因的植株 .     

梨黄粉蚜发生规律及防治技术初探

梨黄粉蚜是近年来直接给梨树生产构成巨大威胁的一种主要优势害虫。为深入了解其发生规律,掌握其生活习性,制定防治对策,近2年来,对其发生规律、生活习性进行了系统观察,摸索出相应的防治对策,筛选出了几种有效农药品种,取得了可喜的成果。     

Kinesin moves by an asymmetric hand-over-hand mechanism

Kinesin is a double-headed motor protein that moves along microtubules in 8-nanometer steps. Two broad classes of model have been invoked to explain kinesin movement: hand-over-hand and inchworm. In hand-over-hand models, the heads exchange leading and trailing roles with every step, whereas no such exchange is postulated for inchworm models, where one head always leads. By measuring the stepwise motion of individual enzymes, we find that some kinesin molecules exhibit a marked alternation in the dwell times between sequential steps, causing these motors to "limp" along the microtubule. Limping implies that kinesin molecules strictly alternate between two different conformations as they step, indicative of an asymmetric, hand-over-hand mechanism.     

2009年大豆分子标记及辅助选择育种研究进展

DNA分子标记技术、QTL定位和分子辅助选择育种的应用对优质多抗大豆品种的快速选育具有十分重要的意义。诸多重要的性状包括大豆形态性状、产量性状、品质性状、生态性状、抗生物及非生物胁迫性状等的相关QTL研究和利用在国内外均有报道。随着功能基因组学的发展和实验技术手段的进步,分子标记和QTL研究向基于基因组功能区段的新型分子标记以及QTL的精细定位研究转移已成为发展方向。目前,国外相关研究已经取得了显著成效。我国现阶段偏重于利用随机分子标记进行QTL研究,对于先进的技术手段还在起步或摸索阶段,与真正实现高效的分子辅助选择育种的目标还有一定距离。文章就2009年国内外大豆分子标记技术、分子标记辅助育种技术及应用的发展动态做一综述。     

苹果转基因研究进展

近年来,苹果遗传转化研究取得了较大的进展,已有多种标记基因和目的基因成功转入苹果中并且得到稳定表达和遗传。农杆菌介导法是苹果上应用的主要转化方法,叶片再生不定芽途径是被广泛应用的受体系统。影响农杆菌介导成功与否的因素很多,文章从转化方法、叶片再生能力、菌株类型以及农杆菌侵染条件等方面综述了目前有关研究成果,指出目前依然存在转化效率不高、外源基因表达强度不够、对转化植株的选择不够重视等诸多问题。     

Conversion of Unc104/KIF1A kinesin into a processive motor after dimerization

Unc104/KIF1A belongs to a class of monomeric kinesin motors that have been thought to possess an unusual motility mechanism. Unlike the unidirectional motion driven by the coordinated actions of the two heads in conventional kinesins, single-headed KIF1A was reported to undergo biased diffusional motion along microtubules. Here, we show that Unc104/KIF1A can dimerize and move unidirectionally and processively with rapid velocities characteristic of transport in living cells. These results suggest that Unc104/KIF1A operates in vivo by a mechanism similar to conventional kinesin and that regulation of motor dimerization may be used to control transport by this class of kinesins.     

Gas-phase ion chemistry

Progress has been made in the understanding of potential energy surfaces for unimolecular ion dissociations and ion-molecule reactions. With recent advances in instrumentation, many new techniques have been developed to generate and study ions, ion-molecule complexes, and large ionic clusters. Developments in ion spectroscopy have enabled considerable advances to be made in the determination of ion structures.     

抗盐碱转基因大豆对根际与非根际土壤氨氧化古菌多样性的影响

采用PCR—DGGE技术,研究了抗盐碱转基因大豆(SRTS)对根际与非根际土壤氨氧化古菌(AOA)群落多样性的影响。结果表明,在非根际土壤中,SRTS的氨氧化古菌DGGE条带数、多样性指数显著高于其受体亲本黑农35和其他两种大豆处理,而均匀度指数较低;在根际土壤中,SRTS的DGGE条带数和多样性指数均高于其受体亲本,但并不显著,其均匀度指数则显著高于其他处理;每种大豆自身根际与非根际比较显示,SRTS非根际氨氧化古菌DGGE条带数、多样性指数明显高于根际,均匀度指数却低于根际,而其受体亲本与其他两个处理反之。聚类分析结果表明,SRTS的DGGE带谱与其他大豆处理差异较大,且自身非根际与根际处理差异显著,与其受体亲本黑农35相似性很低。测序结果表明,在SRTS处理中特有条带12、15和优势条带13、14均属于Uncultured crenarchaeote。在盐碱土壤生态系统中,SRTS提高了非根际土壤氨氧化古菌群落的多样性,但对根际土壤中氨氧化古菌的群落多样性有一定的抑制作用。