Collaborative Research: Isothermal Phase Transition in Lipid Vesicles and Swell-Burst Cycles

合作研究：脂质囊泡中的等温相变和膨胀-爆裂循环

• 批准号: 1505056
• 负责人: Atul Parikh
• 金额: $ 21万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-05-01 至 2020-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1505056&HistoricalAwards=false
• 关键词: Collaborative; Research; Isothermal; Phase; Transition

In this project the PI, using a combination of theory, simulations and experiments, will investigate the complexities of lipid membranes. The project combines concepts from the fields of polymer physics, membrane mechanics and bioengineering, surface and interface science, and soft condensed matter to study the organization of biological membranes. The modeling efforts will develop new and novel mathematics and new numerical schemes to solve the resulting differential equations. The current understanding of how multi-component giant unilamellar vesicles (GUVs) respond to osmotic pressure differentials is incomplete, and experimental observations indicate that a non-linear model coupling membrane dynamics with 3D fluid flow is needed to fully explain the non-linearities of the system. Developing this theoretical framework and providing insight into the underlying physics is crucial for the understanding of how membranes undergo morphological transitions. These models will explain existing experiments and also predict membrane response to different osmotic loads and membrane compositions. Understanding this process is important for better experimental design of in vitro reconstituted systems such as vesicles and also cellular systems. The work is inherently interdisciplinary, using mathematics and physics in biological systems. Both fields will benefit from this approach to studying biological phenomena; the theory will be grounded in experiments and also make predictions to design future experiments. This research will be integrated into the teaching efforts of the PIs in developing new courses at the interface of engineering and biology. The PIs will continue their efforts in enhancing diversity in the UC system while pursuing the research program. Biological membranes are inherently heterogeneous mixtures of lipids and proteins. A key characteristic of this heterogeneity is the coexistence of liquid-ordered and liquid-disordered phases. This coexistence is thought to be the key organizing principle for the formation of lipid rafts. Studying the formation and organization of the different phases in cellular system is experimentally challenging, given the complex nature of the cells. Giant unilamellar vesicles with controlled compositions, allow us to study lipid behavior in bilayer membranes and gain insight into phase behavior which is important for understanding cellular membranes. Although GUVs are used widely experimentally, our theoretical understanding of lipid phase separation remains rudimentary, since existing models focus on the line tension between preexisting domains and not on domain growth and swell-burst cycles, which are the features observed experimentally. The objectives of this project are to formulate quantitative models of isothermal phase separation and swell-burst cycle in multi-component GUVs and test model predictions experimentally. STUDY 1-DYNAMICS OF SOLUTE EFFLUX. We will use theory, simulations, and experiments to understand the factors that control pore radius, vesicle radius, and the lifetime of the pore. STUDY 2-PHASE SEPARATION IN OSMOTICALLY STRESSED VESICLES. Using a viscoelastic model of multi-component lipid membranes, we will investigate the role of governing energetics in domain growth versus true phase transitions. We will experimentally test the model predictions by tuning the osmotic pressure difference, lipid composition, and sample temperature. STUDY 3-COUPLING BETWEEN DOMAIN FORMATION AND SWELL-BURST CYCLES. In this study, we will develop the mathematical framework to model the complete dynamics of the oscillatory phase separation coupled with the swell-burst cycle observed in the preliminary experiments. This model will combine the dynamics of pore formation outlined in Study 1, with the domain growth model including membrane viscosity in Study 2. The significance of the proposed activities lies in its promise to not only elucidate the fundamental properties of mixtures of lipids reduced dimensional, bilayer configuration but also furnish design principles for designing synthetic protocellular compartments for applications spanning in vitro production of proteins, chemistry in confinement, and delivery of biomedically relevant cargo (e.g., enzymes, drugs, and imaging agents). Using a combination of theory, simulations and experiments, this work will be able to provide insight into the complexities of lipid membranes. The long-term impact of the proposed activities stems from the fact that the project combines concepts from the fields of polymer physics, membrane mechanics and bioengineering, surface and interface science, and soft condensed matter. The modeling efforts outlined here will result in new and novel mathematics and new numerical schemes to solve the resulting differential equations.

在这个项目中，PI结合了理论，模拟和实验，将研究脂质膜的复杂性。该项目结合了聚合物物理学，膜力学和生物工程，表面和界面科学领域的概念，以及软凝结物质，以研究生物膜的组织。建模工作将开发新的和新颖的数学和新的数值方案，以解决所得的微分方程。当前对多组分巨型单层囊泡（GUV）如何响应渗透压差异的理解是不完整的，实验观察结果表明，需要与3D流体流动的非线性模型耦合膜动力学，以充分解释系统的非线性。开发这一理论框架并提供对基本物理学的见识对于理解膜如何进行形态学转变至关重要。这些模型将解释现有的实验，并预测膜对不同渗​​透载荷和膜组成的反应。了解此过程对于更好地实验性设计的体外重构系统（例如囊泡和细胞系统）很重要。这项工作本质上是跨学科的，使用生物系统中的数学和物理学。这两个领域都将受益于研究生物学现象。该理论将基于实验，并为设计未来的实验做出预测。这项研究将纳入PI的教学工作，以在工程和生物学的界面开发新课程中。 PI将继续努力在进行研究计划时增强UC系统的多样性。生物膜是脂质和蛋白质的异质混合物。这种异质性的关键特征是液体排序和液态阶段的共存。这种共存被认为是形成脂质筏的关键组织原理。考虑到细胞的复杂性质，研究细胞系统中不同阶段的形成和组织在实验上具有挑战性。具有控制成分的巨型单层囊泡，使我们能够研究双层膜中的脂质行为，并洞悉相位行为，这对于理解细胞膜很重要。尽管GUV是在实验中广泛使用的，但我们对脂质期分离的理论理解仍然是基本的，因为现有模型集中在先前存在的域而不是域的生长和膨胀燃烧周期之间的线张力上，这是实验上观察到的特征。该项目的目的是在多组分GUV中制定等温相分离和膨胀爆发周期的定量模型，并通过实验性地进行测试模型预测。研究溶质外排的1-动力学。我们将使用理论，模拟和实验来了解控制孔半径，囊泡半径和孔的寿命。研究在渗透压囊泡中的2相分离。使用多组分脂质膜的粘弹性模型，我们将研究控制能量在域生长与真实相变的作用。我们将通过调整渗透压差，脂质组成和样品温度来实验测试模型预测。研究结构域形成和膨胀周期之间的3耦合。在这项研究中，我们将开发数学框架，以建模振荡相分离的完整动力学，并在初步实验中观察到的肿胀燃烧周期。该模型将结合研究1中概述的孔形成的动态，领域的生长模型包括研究2中的膜粘度。所提出的活动的重要性在于其不仅阐明脂质混合物的基本特性的承诺，还可以降低二级构型的构造，还可以跨越二层构型，还提供了跨度的跨性跨度的原理，该原理是指定性的，该原理具有构成的构成构成的构成构成的构成构成，同时构成了合成的构成，该构成了合成的构成，并构成了构成的构成构成，并构成了合成的构成构成的构造，并降低了合成的构成构成的构成范围。限制化学和生物医学相关货物（例如酶，药物和成像剂）的递送。结合理论，模拟和实验，这项工作将能够洞悉脂质膜的复杂性。拟议活动的长期影响源于以下事实：该项目结合了聚合物物理学，膜力学和生物工程，表面和界面科学以及软凝结物的概念。此处概述的建模工作将导致新的和新颖的数学和新的数值方案来解决所得的微分方程。