As solute molecules permeate into a vesicle due to a concentration difference across its membrane, the vesicle swells through osmosis. The swelling can be divided into two stages: (a) an "ironing" stage, where the volume-to-area ratio of the vesicle increases without a significant change in its area; (b) a stretching stage, where the vesicle grows while remaining essentially spherical, until it ruptures. We show that the crossover between these two stages can be represented as a broadened continuous phase transition. Consequently, the swelling curves for different vesicles and different permeating solutes can be rescaled into a single, theoretically predicted, universal curve. Such a data collapse is demonstrated for giant unilamellar POPC vesicles, osmotically swollen due to the permeation of urea, glycerol, or ethylene glycol. We thereby gain a sensitive measurement of the solutes' membrane permeability coefficients, finding a concentration-independent coefficient for urea, while those of glycerol and ethylene glycol are found to increase with solute concentration. In addition, we use the width of the transition, as extracted from the data collapse, to infer the number of independent bending modes that affect the thermodynamics of the vesicle in the transition region.
脂质双层对渗透胁迫的反应是细胞功能的重要组成部分。之前，在[Oglecka et al. 2014]中，我们报告了暴露于低渗介质的细胞大小的巨型单层囊泡（GUV）通过经历一系列循环的肿胀和破裂事件（与膜的组成自由度相结合）对渗透压攻击作出反应。在这里，我们试图加深我们的定量理解的基本脉动行为的GUV在低渗条件下，通过推进一个全面的理论模型囊泡动力学。该模型定量捕获我们的实验测量的溶胀-爆裂参数为单组分GUV，并揭示，热波动使速率依赖性孔成核，驱动溶胀-爆裂周期的动态。我们进一步确定新的脉动动力学和GUV属性之间的标度关系。我们的研究结果提供了一个基本的框架，有可能指导未来的调查渗透胁迫下的非平衡动力学的囊泡。
Osmotically Induced Shape Changes in Membrane Vesicles
Kansas State University（堪萨斯州立大学）；NewOrbit Space Ltd（NewOrbit空间有限公司）；University of Sheffield（谢菲尔德大学）；Kaplan International College（凯伦国际学院）；Université Paris-Saclay（巴黎萨克雷大学）
Renormalized mechanics and stochastic thermodynamics of growing vesicles
The James Franck Institute, University of Chicago（芝加哥大学詹姆斯·弗兰克研究所）；Department of Chemistry, University of Chicago（芝加哥大学化学系）；Engineering Sciences and Applied Mathematics, Northwestern University（西北大学工程科学与应用数学系）
