Biomolecular Materials: Structure, Phase Behavior, & Interactions

ID: MPS/DMR/BMAT(7623) 1101900 PI: Safinya， Cyrus ORG: UC Santa barbara标题：生物分子材料：结构，相行为和相互作用本提案的目的是发展对分子间作用力和丝状蛋白（特别是神经丝和微管）组装的结果结构的基本理解，这些丝状蛋白来自神经元树突和轴突的细胞骨架（神经元用来接收和发送信号给邻近神经元的延伸）。该方案结合了PI使用的最先进的同步加速器x射线散射、x射线渗透压、光学和电子显微镜技术，并与co-PI的现代建模密切相关。微管相关蛋白（MAP） tau是一种丰富的非结构化生物聚合物，含有阴离子和阳离子氨基酸残基，通过静电相互作用与轴突中的微管结合并稳定微管。虽然MAP-tau在调节微管之间相互作用中的确切作用尚不清楚，但已经确定的是，tau和微管之间的异常相互作用（例如，由于tau突变或过度磷酸化）总是导致细胞骨架崩溃和神经退行性变。在模拟轴突和树突不同局部环境（即三种神经丝侧臂的不同组成和MAP-tau的存在或不存在）的系统中，通过带电的神经丝侧臂和MAP-tau介导的结构和丝状间相互作用被提出了实验。本提案的具体目标是：(1)阐明生物和合成多价反离子在抑制排斥屏障中的作用，排斥屏障阻止了MAP-tau介导的微管之间的短程吸引，(2)通过发现结构域缺失（通过截断的tau构建体）如何改变tau介导的微管组装来揭示MAP-tau的结构功能特性。(3)研究微管和神经丝共组装混合物中神经元细胞骨架细丝之间的分子间相互作用及其产生的结构；(4)建立两个对立的多两性刷子（模拟神经丝和微管的结构）之间的力的定量模型，以密切捕捉由MAP-tau介导的微管之间相互作用的生物物理学，不同神经丝侧臂之间；以及在神经丝侧臂和MAP-tau之间。除了增强我们对神经细胞骨架的认识外，拟议的研究将进一步加深我们对带电聚合物系统的理解，这是一个非常重要的软物质和生物物质领域，还有很多有待了解的地方。更广泛的影响：拟议的研究将导致对大自然如何利用相互竞争的分子间力量（例如，短距离的吸引力和长距离的排斥力）在神经细胞的长延伸中组装不同的丝状结构的全面理解，以赋予关键功能，如机械稳定性和促进物质的运输。从研究中获得的理解（例如，关于负责纤维间相互作用的特定化学成分）将使更广泛的科学界能够采用合理的方法设计合成积木模拟物，以构建由控制分子间相互作用的分子水平内置功能产生的分层结构。仿生结构，反过来，预计有重要的技术应用，例如，作为模板的小型化材料与纳米生物技术的应用。pi的生物材料研究工作是多学科的，教育和培训本科生、研究生和博士后研究人员，他们需要用现代方法来解决物理、化学、工程和生物学之间的重要问题。所获得的跨学科技能为学员在学术界、国家实验室和工业界的职业生涯做好准备。主要研究人员积极参与加州大学圣巴巴拉分校与社区学院和圣巴巴拉以外的学院和大学的外展项目。这些项目包括纳米系统科学与工程技术实习、加州少数民族参与联盟、科学与工程研究实习、国际科学与工程合作实习以及教师研究经验。这项活动使pi能够在科学和工程的多学科方法方面培训广泛的学生和教师。

ID: MPS/DMR/BMAT(7623) 1101900 PI: Safinya, Cyrus ORG: UC Santa BarbaraTitle: Biomolecular Materials: Structure, Phase Behavior, and InteractionsINTELLECTUAL MERIT: The aim of this proposal is to develop a fundamental understanding of the intermolecular forces and resulting structures in assemblies of filamentous proteins (in particular, neurofilaments and microtubules) derived from the cytoskeleton of neuronal dendrites and axons (the extensions used by neurons to receive and send signals to neighboring neurons). The proposal combines state-of-the-art synchrotron x-ray-scattering, x-ray-osmotic pressure, and optical and electron microscopy techniques used by the PI, and in parallel, closely related modern modeling by the co-PI. Experiments are proposed to study forces between microtubules mediated by microtubule-associated-protein (MAP) tau, an abundant unstructured biological polymer containing anionic and cationic amino acid residues, which binds to (via electrostatic interactions) and stabilizes microtubules in axons. While the precise role of MAP-tau in modulating interactions between microtubules is unclear, it is well established that aberrant interactions between tau and microtubules (e.g., due to tau mutations or over-phosphorylation) invariably lead to collapse of the cytoskeleton and neurodegeneration. Experiments are proposed to understand the structures and inter-filamentous interactions, mediated by charged neurofilament-sidearms and MAP-tau, in systems which closely mimic the distinct local environments of axons and dendrites (i.e., with different composition of the three neurofilament-sidearms and the presence or absence of MAP-tau). The specific aims of this proposal are (1) to elucidate the role of biological and synthetic multivalent counter-ions in suppressing the repulsive barrier, which prevents MAP-tau-mediated short-range attractions between microtubules, (2) to unravel the structure-function properties of MAP-tau by discovering how domain deletions (via truncated tau constructs) alter tau-mediated microtubule assembly, (3) to study the intermolecular interactions and resulting structures between neuronal cytoskeletal filaments in co-assembling mixtures of microtubules and neurofilaments, and (4) to develop quantitative models of forces between two opposing polyampholyte brushes (mimicking the structures of neurofilaments and microtubules) to closely capture the biophysics of interactions between microtubules mediated by MAP-tau, between different neurofilament-sidearms, and between neurofilament-sidearms and MAP-tau. Aside from enhancing our knowledge of the nerve cell cytoskeleton, the proposed research will further our understanding of charged-polymeric systems, a very important field of soft and biological matter, where much remains to be understood.BROADER IMPACTS: The proposed studies will lead to a comprehensive understanding of how nature makes use of competing intermolecular forces (e.g., attractions at short distances and repulsions at longer distances) to assemble distinct filamentous structures within the long extensions of nerve cells to impart critical functionalities such as mechanical stability and facilitated transport of materials. The understanding gleaned from the studies (e.g., about the specific chemical moieties responsible for inter-filament interactions) will enable the broader scientific community to employ a rational approach in the design of synthetic building-block mimics for constructing hierarchical structures arising from the built-in functionality at the molecular level that control intermolecular interactions. The biomimetic structures, in turn, are expected to have important technological applications, for example, as templates for miniaturized materials with applications in nano-biotechnology. The biomaterials research effort of the PIs is multidisciplinary and educates and trains undergraduate and graduate students and postdoctoral researchers in modern methodologies required to address important problems at the interface between physics, chemistry, engineering, and biology. The acquired interdisciplinary skills prepare the trainees for careers in academe, national laboratories, and industry. The principal investigators actively participate in UCSB Outreach Programs with the community colleges and with colleges and universities outside of Santa Barbara. The programs include the Internships in Nanosystems Science and Engineering Technology, California Alliance for Minority Participation, Research Internship in Science and Engineering, Cooperative International Science and Engineering Internships, and the Research Experience for Teachers. This activity allows the PIs to train a broad spectrum of students and teachers in multidisciplinary methods of science and engineering.