Self-assembly and motility far from equilibrium

自组装和运动远离平衡

• 批准号: 1104637
• 负责人: Andrea Liu
• 金额: $ 54.5万
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-09-15 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1104637&HistoricalAwards=false
• 关键词: Self; assembly; motility; far; equilibrium

Technical SummaryThe Division of Materials Research and the Division of Molecular and Cellular Biosciences contribute funds to this award. This award supports theoretical and computational research and education to understand the physical mechanism by which living organisms propel themselves. Certain motile biological objects, such as the bacterium Listeria monocytogenes and replicating chromosomes in asymmetric bacteria like Caulobacter crescentus and Vibrio cholerae, generate their propulsion by polymerizing or depolymerizing protein filaments. This establishes a concentration gradient in the protein so that there are more filaments on one side of the object than the other. A colloid that maintains an asymmetric concentration of a small solute around it will propel itself through a fluid with a well-defined velocity. This phenomenon, known as self-diffusiophoresis, has been exploited as a means of propulsion of micro- or nano-swimmers. In a typical example, the concentration gradient is controlled by an active region on the colloid that catalyzes a chemical reaction, leading to more product and less reactant near the active region than on the far side of the colloid. The distribution of solute around the colloid is determined by a combination of diffusion and advection. An interaction between the colloid and solute sets up fluid flow that ultimately propels the particle. If the solute is small, so that its diffusion is rapid compared to advection, it is known that only two conditions are needed to achieve motility: the motile object must be able to maintain an asymmetric solute distribution in steady state, and there must be a net interaction between the solute and the object.This award supports theoretical and computational research aimed at understanding a new regime relevant to Listeria, Caulobacter and Vibrio, in which the particle surface catalyzes self-assembly or disassembly rather than a chemical reaction involving simple ions or molecules. Questions to be addressed include: Can the mechanism of self-diffusiophoresis explain effects of biological perturbations that have been studied experimentally? Does it suffice to produce an asymmetric concentration profile of a solute when the solute is large and has an effectively vanishing diffusion constant, as in the biological examples? How does self-diffusiophoresis differ in the advection and diffusion-dominated regimes? Might motility driven by self-assembly and disassembly of filaments be more robust to opposing forces than motility driven by chemical reactions involving simple solutes?The project will train students at the interface of physics and biology to combine biophysics and far-from-equilibrium physics, two areas that have been identified as grand challenges for condensed matter and materials physics in the NRC CMMP-2010 study. Students will be trained both in interdisciplinary model-building and in computational methods, providing versatility for their entry into the workforce.Nontechnical SummaryThe Division of Materials Research and the Division of Molecular and Cellular Biosciences contribute funds to this award. This award supports theoretical and computational research designed to understand how certain living organisms - particularly bacteria or components within bacteria such as chromosomes - propel themselves. Such organisms live in a fluid environment so they must swim. Bacteria such as Listeria monocytogenes, responsible for listeriosis, generate branched filaments at their rear that propel them forward so that they can infect other cells, while chromosomes in Vibrio cholera, responsible for cholera, disassemble protein filaments in front of them in order to move across the cell before the cell divides. It is known that micron-sized particles that are coated on one side with a chemical reaction enabling material such as platinum can propel themselves through a fluid by enabling a chemical reaction at the surface. In that case, an interaction between the product or reactant and the particle surface drives fluid flow that ultimately propels the particles forward. But the interplay of filament assembly and disassembly on fluid flow is very different from that of simple chemical reactions with fluid flow. The aim of this research is to understand the physical mechanism by which the assembly or disassembly of filaments can drive motion, and to explore whether such locomotion might be more robust to physical and biochemical perturbations than the simple reaction-driven locomotion that has been studied in the materials community.Filament-assembly-driven propulsion is key to many immune processes in living organisms, including how immune cells move, how cancer cells spread and how cells migrate during wound healing. A better understanding of the physical mechanism underlying how these cells move may be important to developing ways of helping or hindering them. These biological realizations, which have evolved to be remarkably robust, may also inspire better motile materials such as micro- or nano-swimmers that can move forwards against large opposing forces and may be useful for applications including drug delivery.This award will prepare graduate students for rapidly evolving challenges in the workforce by training them in model-building and computational methods at the intersection of the physical and life sciences. The exposure to different fields and opportunity to work directly with biologists as well as theoretical, computational and experimental physicists will prepare them to collaborate and communicate effectively with colleagues with very different areas of expertise.

技术总结材料研究的部门以及分子和细胞生物科学的划分为该奖项贡献了资金。该奖项支持理论和计算研究和教育，以了解生物体推动自己的物理机制。某些运动生物学对象，例如单核细菌细菌，并在不对称细菌中复制染色体，如caulobacter crescentus和弧菌霍乱，通过聚合或解聚蛋白质的蛋白质丝来产生它们的推进。这在蛋白质中建立了浓度梯度，因此物体的一侧比另一侧有更多的细丝。胶体在其周围保持不对称浓度的胶体将通过具有明确定义的速度的液体推动自身。 这种现象被称为自我植物噬菌体，已被利用为推进微型或纳米 - 温植物的一种手段。 在一个典型的示例中，浓度梯度由胶体上的活性区域控制，胶体上催化化学反应，导致活性区域附近的产物更多，而反应物比胶体的另一侧更少。胶体周围溶质的分布取决于扩散和对流的组合。胶体和溶质之间的相互作用建立了最终推动粒子的流体流动。 If the solute is small, so that its diffusion is rapid compared to advection, it is known that only two conditions are needed to achieve motility: the motile object must be able to maintain an asymmetric solute distribution in steady state, and there must be a net interaction between the solute and the object.This award supports theoretical and computational research aimed at understanding a new regime relevant to Listeria, Caulobacter and Vibrio, in which the particle surface catalyzes自组装或拆卸，而不是涉及简单离子或分子的化学反应。 要解决的问题包括：自我散发性噬菌体的机制可以解释实验研究的生物扰动的影响吗？当溶质较大并且具有有效消失的扩散常数时，产生溶质的不对称浓度谱是否足以产生溶质？ 自我散发性噬菌体在对流和扩散为主导的政权上有何不同？与涉及简单溶质的化学反应驱动的运动能力相比，由丝的运动能力更强大，而涉及简单溶质的运动能力更强大？该项目将在物理学和生物学的界面上培训学生，以将生物物理学和远面平衡物理学结合到凝结物质和材料物质cmmp的两个挑战。学生将接受跨学科模型建设和计算方法的培训，为他们进入劳动力的多功能性提供了多功能性。非技术性总结材料研究的部门以及分子和细胞生物科学的划分为该奖项贡献了资金。该奖项支持理论和计算研究，旨在了解某些生物（尤其是细菌或细菌（例如染色体）中的成分）如何推动自己。 这样的生物生活在液体环境中，因此必须游泳。 负责李斯特氏病的细菌（如单核细胞增生李斯特菌）在其后部产生分支细丝，使它们向前促进它们，以便它们可以感染其他细胞，而弧菌中的染色体，负责霍乱，负责霍乱的霍乱，拆卸蛋白质的蛋白质，以便在细胞分离之前移动细胞。 众所周知，用化学反应涂在一侧的微米大小的颗粒，允许铂金等化学反应可以通过在表面上实现化学反应来推动自己的液体。 在这种情况下，产物或反应物与颗粒表面之间的相互作用驱动流体流，最终推动颗粒前进。 但是，细丝组件和在流体流量上拆卸的相互作用与流体流动的简单化学反应的相互作用非常不同。 这项研究的目的是了解细丝的组装或拆卸可以推动运动的物理机制，并探索这种运动是否可能比在材料社区中研究的简单反应驱动的运动更适合物理和生物化学扰动更强大。细胞在伤口愈合过程中迁移。 更好地了解这些细胞如何移动的物理机制对于开发帮助或阻碍它们的方式可能很重要。 这些已经发展为非常强大的生物学实现，也可能激发更好的运动材料，例如微型或纳米 - 温杂种，可以向大型对立力量推动，并且可能对包括药物提供的应用有用。这项奖项将为研究生做好准备，以使研究生在模型和计算方法和计算方法和计算方法中培训他们在劳动中的迅速发展挑战，并在锻炼中进行了研究和实例化的方法，并将其做好准备。 接触不同领域和直接与生物学家合作的机会以及理论，计算和实验物理学家将准备与具有非常不同专业知识领域不同的同事进行合作和有效沟通的准备。