Curvature-dependent Lipid Organization at Surfaces

1034569 Parikh这个建议测试了这样一个概念，即动态呈现拓扑化学线索可以触发支持的脂双层中依赖曲率的空间组织和重塑。在生物膜中，双层曲率不是细胞活动的被动结果。相反，它代表着一种主动的构象转换，在空间上调节许多细胞表面的相互作用和细胞内的运输。尽管它们很重要，但提供静态和动态曲率的可控引入的模型膜配置是稀少的。这项工作的重点是设计和使用模型膜配置，使之能够主要使用EPI和共聚焦荧光、光学椭偏和原子力显微镜的常规定量应用相结合的方式，在纯基于脂质的简单膜环境中对曲率、组成和动力学之间的耦合进行基础研究。一些实验还利用了傅里叶变换红外振动光谱和差示扫描量热法。这项工作提出了由局部分子组织(例如化学组成)和膜物理性质(例如填充缺陷、相变性质和膜张力)定义的曲率生态位的概念。有人认为，这一利基定位于关键的物理化学相互作用，这些相互作用产生曲率专一性和“曲率传感”能力。这项工作开发并采用了两种平行的模型膜构型，将支撑的脂类双层与(1)可切换的地形弹性底物和(2)平面胶体晶体底物集成在一起。这些平台的类属性质提供了一系列依赖曲率的膜组织、重塑及其功能后果的生物物理研究。其目标集中在三个特定的领域：(1)具有特定分子形状的膜分子的曲率依赖的空间组织和相分离的基础，包括在植物类囊体膜或细菌膜中发现的那些分子；(2)动态再平衡和曲率生态位的形成，通过依赖于时间的膜曲率的引入；(3)膜重塑VAML作用，它产生具有自发曲率的分子，并且曲率在促进水溶性磷脂酶活性方面的作用。这一提议促进了物理科学和生物科学之间迅速增长的合作。它利用分子定义和以波纹表面为模板的超分子生物分子结构，开始解决有关脂质双层中曲率、动力学和组成的耦合的长期存在的问题。拟议中的工作以一种允许研究与教育无缝结合的方式整合了材料科学、表面化学和生物物理学。它寻求以多种方式利用这一机会产生更广泛的影响。首先，有人建议，这项工作将作为发展个人和中心型合作的基础，这些合作受益于理论和计算、生物科学和高分辨率光学工具的应用方面的并行努力。第二，计划的研究活动将有助于促进使用基于物理科学的方法和量化方法来解决生物学上的重要问题。第三，建议的工作将被用来开发一门工程生物学课程，重点是分子水平的设计。第四，该项目的必然组成部分，特别是类囊体膜，为学生提供机会探索他们对知识产权开发的研究和/或在能源和生物学之间发展学术重点。第五，它将有助于正在进行的努力，将团队环境建设为不同科学学科的大熔炉。第六，它将通过本科生和代表不足的群体的参与来加强外联活动。

1034569ParikhThis proposal tests the notion that dynamic presentation of topochemical cues can trigger curvature-dependent spatial organization and remodeling in supported lipid bilayers. In biological membranes, bilayer curvature is not a passive consequence of cellular activity. Rather it represents an active conformational switch to spatially regulate many cell surface interactions and intracellular trafficking. Despite their importance, model membrane configurations that afford controlled introduction of static and dynamic curvatures are sparse. The effort is focused on devising and employing model membrane configurations that allow fundamental investigations of couplings between curvature, composition, and dynamics in purely lipid based, simple membrane environments primarily using a combination of routine quantitative applications of epi and confocal fluorescence, optical ellipsometric, and atomic force microscopies. Some experiments also utilize Fourier transform infrared vibrational spectroscopy and differential scanning calorimetry.Intellectual Merit. The effort proposed advances the concept of curvature-niche defined by the local molecular organization (e.g., chemical composition) and membrane physical properties (e.g., packing defects, phase transition properties, and membrane tension). This niche, it is suggested, localizes key physical chemical interactions whose interplay produces curvature specificity and "curvature-sensing" capabilities. The work develops and employs twoparallel classes of model membrane configuration that integrate supported lipid bilayers with (1)switchable topography elastomeric substrates and (2) planar colloidal crystal substrates. The generic nature of these platforms affords the range of biophysical studies of curvature dependent membrane organization, remodeling, and their functional consequences. The aims are focused on three specific areas: (1) the basis for curvature dependent spatial organization and phase separation of membrane molecules with defined molecular shapes including those found in plant thylakoid or bacterial membranes; (2) dynamic re-equilibration and curvature niche formation via time dependent introduction of membrane curvatures; and (3) membrane remodeling viasphingomyelinase action which generates molecules with spontaneous curvature and role of curvatures in promoting activation of a water soluble phospholipase enzyme.Broader Impact. This proposal contributes to the rapidly growing collaboration between physical and biological sciences. It takes advantage of molecular definition and supramolecular biomolecular structures templated at corrugated surfaces to begin to address long standing questions regarding the coupling of curvature, dynamics, and composition in lipid bilayers. The work proposed integrates materials science, surface chemistry, and biophysics in a manner that allows a seamless integration of research with education. It seeks to exploit this opportunity for broader impact in multiple ways. First, it is suggested that the effort will serve as a base for developing individual and center type collaborations that benefit from parallel efforts in theory andcomputations, biological sciences, and applications of high resolution optical tools. Second, the research activities planned will help advance the use of physical science based approaches and quantitative methods to addressing biologically important problems. Third, the work proposed will be leveraged to develop a course in engineering biology with a focus on molecular level design.Fourth, the corollary components of the project, in particular thylakoid-mimetic membranes, offer students opportunities to explore their research toward intellectual property development and/or develop an academic focus between energy and biology. Fifth, it will help ongoing efforts inbuilding the group environment as a melting pot of disparate scientific disciplines. Sixth, it will enhance outreach activities by the involvement of undergraduate students and underrepresented groups.