Electrophoresis of Filamentous Viruses Through Solid State Nanopores

非技术性：这个奖项由材料研究部的生物材料项目授予布朗大学，目的是研究丝状病毒如何通过极微小的毛孔。这些小孔是通过一层薄薄的氮化硅钻出来的，氮化硅是一种固态材料，因此它们被称为固态纳米孔。本研究使用的病毒属于一类细菌噬菌体，是从受感染的大肠杆菌中分离出来的。这些病毒是长度约一微米、直径仅几纳米的细丝，每一种病毒的大小都相同，因为它由一条DNA链组成，外面覆盖着大约3000份小外壳蛋白。因为外壳蛋白带有几个电荷，所以病毒细丝沿其长度带电。当含有病毒的溶液填满含有单个纳米孔的装置的一侧时，通过在装置上施加电压，病毒可以一个接一个地穿过纳米孔。当病毒通过纳米孔时，它会在短暂但可测量的持续时间内阻止特定数量的电流。该项目的目标是将纳米孔作为工具来研究带电分子如何在纳米孔中移动的微观细节。这项研究基本上包括在精心控制的条件下和一些不同的参数下进行的全面测量。阻止电流的数量和移位的速度是如何随着溶液中加入的盐量、纳米孔的大小和施加的电压等参数而变化的，这可以告诉我们许多关于物理过程的信息，一直到分子尺度。尽管这项研究在概念上很简单，但所获得的知识可能具有深刻的技术含义。例如，它可能导致有效检测和分类各种病毒株的微型设备。该项目还将为研究生和本科生提供多学科培训。PIs和研究生还计划通过Brown Science Prep计划提供客座讲座、进行演示和主持实验室参观，所有这些都是为了扩大实验室研究对周围地区K-12学生和普通公众的影响。技术：在这个项目中，丝状病毒将被用来研究通过纳米尺度的毛孔驱动电泳的基本物理。丝状病毒的物理性质，包括它们的电荷密度、硬度和长度，都是精确已知的，而且很容易调节。这种控制使我们能够在单分子水平上系统地测试纳米孔内的电泳理论模型。计划中的研究包括测量捕获过程、阻塞的电流数量、移位速度和单个移位时间的分布。在这项研究中，将研究在一定的驱动电压范围内，灯丝的硬度对移位速度的影响。此外，还将确定导致移位速度分散的因素。实验结果将与基于耦合的Navier-Stokes和Poisson Boltzmann方程的理论计算进行比较，也将与由朗之万动力学驱动的计算机模拟进行比较。通过解决纳米孔转移的各个方面，包括捕获过程、电动拉力和与之相反的粘性阻力，计划中的实验将为已建立的理论模型提供定量测试。因此，参与该项目的学生将获得尖端纳米技术领域的全面培训。计划中的外展工作由Brown Science Prep计划协调，重点是通过客座讲座、实验室参观和演示以及在线视频将物理知识与设备技术联系起来。

Non-technical: This award by the Biomaterials program in the Division of Materials Research to Brown University is to study how filamentous viruses pass through extremely tiny pores. The pores are drilled through a thin layer of silicon nitride, which is a solid-state material and why they are referred to as solid-state nanopores. The viruses being used for this study belong to a class of bacterial phage and are isolated from infected E. coli. The viruses are skinny filaments of about one micrometer in length and only a few nanometers in diameter, and each one is identical in size because it consists of a single DNA chain coated by about three thousand copies of a small coat protein. Because the coat protein carries a few charges, the virus filament is charged along its length. When a solution containing the virus fills one side of a device containing a single nanopore, viruses can be driven through the nanopore, one by one, by applying a voltage across the device. When a virus passes through the nanopore, it blocks a characteristic amount of current for a brief but measurable duration. The goal of this project is to use the nanopore as a tool to study in microscopic detail how stiff charged molecules move through nanopores. This study essentially consists of comprehensive sets of measurements under carefully controlled conditions and with a number of different parameters. How the amount of current blocked and the speed of translocation change with parameters such as the amount of salt added to the solution, the size of the nanopore, and the voltage applied can tell us a great deal about the physical processes at play, all the way down to molecular scale. In spite of the conceptual simplicity of the study, the knowledge acquired can have profound technological implications. It may, for instance, lead to tiny devices for efficiently detecting and sorting various virus strains. The program will also provide multidisciplinary training of graduate and undergraduate students. The PIs and the graduate students have also planned, through the Brown Science Prep program, to deliver guest lectures, perform demonstrations, and host lab tours, all in order to broaden the impact of laboratory research on the surrounding area K-12 students and the general public. Technical: In this project, filamentous viruses will be used to study the fundamental physics of driven electrophoresis through nanoscale pores. The physical properties of filamentous viruses, including their charge density, their stiffness, and their length, are both precisely known and easily tunable. That control enables us to systematically test theoretical models of electrophoresis inside a nanopore at the single-molecule level. The planned study includes measurements of the capture process, the amount of current blocked, the translocation speed, and the spread of individual translocation times. With this study, the effects of filament stiffness on translocation speed under a range of driving voltages will be studied. In addition, factors that account for the dispersion in translocation speed will also be determined. The experimental results will be compared with theoretical calculations based on the coupled Navier-Stokes and Poisson Boltzmann equations, and also compared with computer simulations driven by Langevin dynamics. By addressing every facet of nanopore translocations, including the capture process, the electrokinetic pulling force, and the viscous drag that opposes it, the planned experiments will provide quantitative tests of the established theoretical models. Thus, students working on the program will acquire comprehensive training in the cutting-edge, nano-technology field. The planned outreach efforts, coordinated by the Brown Science Prep program, focus on connecting physics knowledge with device technology, via guest lectures, lab tours, and demos both live and through online videos.