Lipid membrane microrheology

脂质膜微流变学

• 批准号: 1006171
• 负责人: Raghuveer Parthasarathy
• 金额: $ 37.5万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-15 至 2014-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1006171&HistoricalAwards=false
• 关键词: Lipid; membrane; microrheology

ID: MPS/DMR/BMAT(7623) 1006171 PI: Parthasarathy, Raghuveer ORG: University of OregonTitle: Lipid Membrane MicrorheologyINTELLECTUAL MERIT: Lipid membrane fluidity is not well understood and membrane viscosity, the key property that describes fluid response, remains poorly quantified. This proposal describes a coordinated experimental and theoretical program that will illuminate lipid bilayer viscosity and viscoelastic response. Experimentally, lipid membranes will be probed using recently developed methods of two point microrheology, in which dynamic correlations between the trajectories of Brownian tracer particles provide insights into the physics of complex fluids. This approach has never before been applied to lipid membranes. The experiments will involve high-speed video microscopy of nanoparticles linked to planar, unsupported lipid bilayers, followed by image analysis and particle tracking. Theoretical work will analytically extend recent models of the response of ideal two-dimensional fluids to encompass elasticity, viscoelasticity, and tension ¨C key physical properties of consequence to membranes. The resulting theoretical framework will enable quantitative maps between experimentally observed tracer dynamics and the underlying collective dynamics of membranes. The studies target three important membrane systems: (1) Experiments will address homogenous lipid bilayer membranes to correlate viscosity with molecular structure and temperature. Structural studies will examine the dependence of viscosity on the lipids¡¯ acyl chain length, which will reveal whether the hydrophobic core or the hydrophilic headgroup dominates the fluid response. More fundamentally, the data together with new theoretical models will quantify the extent to which lipid membranes behave as viscous versus viscoelastic fluids. (2) The project will also study phase-separated membranes. Cellular membranes are not homogenous in composition, a feature that is believed to help govern protein©\protein interactions. The mechanical consequences of heterogeneity remain poorly understood. Experiments will therefore probe viscosity in model bilayers that, below a critical temperature, exhibit cholesterol©\dependent phase separation into coexisting fluid phases. (3) Finally, the PI will investigate asymmetric membranes. The two lipid leaflets of cellular membranes differ with respect to composition. By constructing asymmetric lipid bilayer membranes, the proposed studies will examine the consequences of asymmetry and the existence mechanical coupling across the leaflets.BROADER IMPACTS: This project will advance the experimental methodology and the theory of viscous and viscoelastic flow in biological lipid membranes. A better understanding of membrane protein diffusion and assembly and of the mechanism of lipid domain formation should emerge. The PI has developed and will continue to deliver a general education course, The Stuff of Life, that explores biophysics for non-science members. Through readings, discussions, and hands©\on exercises, students explore the physical properties of biological materials and the constraints these properties place on living organisms. The course includes discussions of the interplay between physics and biology, of how new modes of experimental analysis (e.g., particle tracking) enable new discoveries, and of the similarities between biomaterials (e.g. membranes) and non©\biological soft matter (e.g. soap films). He will continue to lead efforts in his Department to organize weeklong Physics Day Camps for low economic status high school students. His lab will host undergraduate students participating in an REU program targeting female physical sciences students and students from another program that brings community college students to the campus for a summer research experience. As co-PI on an NSF-sponsored GK-12 project, he directs an activity that partners University of Oregon graduate students with schools in remote Oregon school districts to introduce inquiry-driven science curriculum elements, including science kits that remain with the participating schools.

ID：MPS/DMR/BMAT（7623）1006171 PI：Parthasarathy，Raghuveer ORG：俄勒冈大学标题：脂质膜微观流变学知识优势：脂质膜流动性尚未得到很好的理解，膜粘度，描述液体反应的关键属性，仍然很难量化。 该建议描述了一个协调的实验和理论方案，将照亮脂双层粘度和粘弹性响应。 在实验上，脂质膜将使用最近开发的两点微观流变学的方法进行探测，其中布朗示踪粒子的轨迹之间的动态相关性提供了对复杂流体的物理学的见解。 这种方法以前从未应用于脂质膜。 这些实验将涉及连接到平面，无支撑脂质双层的纳米颗粒的高速视频显微镜，然后进行图像分析和颗粒跟踪。 理论工作将分析性地扩展理想二维流体响应的最新模型，使其包括弹性、粘弹性和张力--这些是膜的关键物理性质。 由此产生的理论框架将使实验观察到的示踪剂动态和膜的基本集体动态之间的定量映射。 本研究针对三个重要的膜系统：（1）实验将针对均匀的脂质双层膜，以关联粘度与分子结构和温度。 结构研究将检查粘度对脂酰基链长度的依赖性，这将揭示是疏水核心还是亲水头基主导流体响应。 更重要的是，这些数据与新的理论模型将量化脂膜表现为粘性流体与粘弹性流体的程度。 (2)该项目还将研究相分离膜。 细胞膜在组成上是不均匀的，这是一个被认为有助于控制蛋白质-蛋白质相互作用的特征。 异质性的机械后果仍然知之甚少。 因此，实验将探测模型双层中的粘度，所述模型双层在临界温度以下表现出胆固醇依赖性相分离成共存的流体相。 (3)最后，PI将研究不对称膜。细胞膜的两个脂质小叶在组成上不同。 通过构建不对称的脂质双层膜，所提出的研究将检查不对称的后果和存在的机械耦合在leafles.BroADER IMPLEMENTARY：该项目将推进生物脂质膜中的粘性和粘弹性流动的实验方法和理论。 一个更好的理解膜蛋白的扩散和组装和脂质结构域形成的机制应该出现。 PI已经开发并将继续提供通识教育课程，生命的东西，探索非科学成员的生物物理学。 通过阅读、讨论和动手练习，学生探索生物材料的物理特性以及这些特性对生物体的限制。 该课程包括讨论物理学和生物学之间的相互作用，如何实验分析的新模式（例如，粒子跟踪）使得能够进行新的发现，以及生物材料（例如膜）和非生物软物质（例如肥皂膜）之间的相似性。他将继续领导他的部门努力组织为期一周的物理日营低经济地位的高中学生。 他的实验室将接待本科生参加一个REU计划，目标是女物理科学学生和另一个计划的学生，该计划将社区大学的学生带到校园进行夏季研究体验。 作为NSF赞助的GK-12项目的共同PI，他指导了一项活动，该活动将俄勒冈州大学的研究生与偏远俄勒冈州学区的学校合作，以引入探究驱动的科学课程元素，包括参与学校的科学工具包。