In this work we demonstrate how the first order phase transition in giant unilamellar vesicles (GUVs) can function as a trigger for membrane fission. When driven through their gel-fluid phase transition GUVs exhibit budding or pearl formation. These buds remain connected to the mother vesicle presumably by a small neck. Cooling these vesicles from the fluid phase (T>Tm) through the phase transition into the gel state (T<Tm), leads to complete rupture and fission of the neck, while the mother vesicle remains intact. Pearling tubes which formed upon heating break-up and decay into multiple individual vesicles which then diffuse freely. Finally we demonstrate that mimicking the intracellular bulk viscosity by increasing the bulk viscosity to 40cP does not affect the overall fission process, but leads to a significant decrease in size of the released vesicles.
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。
We study a synthetic system of motile Escherichia coli bacteria encapsulated inside giant lipid vesicles. Forces exerted by the bacteria on the inner side of the membrane are sufficient to extrude membrane tubes filled with one or several bacteria. We show that a physical coupling between the membrane tube and the flagella of the enclosed cells transforms the tube into an effective helical flagellum propelling the vesicle. We develop a simple theoretical model to estimate the propulsive force from the speed of the vesicles, and demonstrate the good efficiency of this coupling mechanism. Togeth…
What can we learn about the lipid vesicle structure from the small-angle neutron scattering experiment? (Investigation DMPC vesicle structure by small angle neutron scattering)
Biological membranes constantly change their shape in response to external stimuli, and understanding the remodeling and stability of vesicles in heterogeneous environments is therefore of fundamental importance for a range of cellular processes. One crucial question is how vesicles respond to external osmotic stresses, imposed by differences in solute concentrations between the vesicle interior and exterior. Previous analyses of the membrane bending energy have predicted that micron-sized giant unilamellar vesicles (GUVs) should become globally deformed already for nanomolar concentration dif…
Enhanced manipulation and analysis of bio-particles using light confined in nano-scale dielectric structures has proceeded apace in the last several years. Small mode volumes, along with the lack of a need for bulky optical elements give advantages in sensitivity and scalability relative to conventional optical manipulation. However, manipulation of lipid vesicles (liposomes) remains difficult, particularly in the sub-micron diameter regime. Here we demonstrate the optical trapping and transport of sub-micron diameter liposomes along an optical nanofiber using the nanofiber mode's evanescent f…
Lipid bilayer membranes are the fundamental biological barriers that permit life. The bilayer dynamics largely participates in orchestrating cellular workings and is characterized by substantial stability together with extreme plasticity that allows controlled morphological/topological changes. Modeling and understanding the topological change of vesicle-like membrane at the scale of a full cell has proved an elusive aim. We propose and discuss here a continuum model able to encompass the fusion/fission transition of a bilayer membrane at the scale of a Large Unilamellar Vesicle and evaluate t…
We present a simple method to produce giant lipid pseudo-vesicles (vesicles with an oily cap on the top), trapped in an agarose gel. The method can be implemented using only a regular micropipette and relies on the formation of a water/oil/water double droplet in liquid agarose. We characterize the produced vesicle with fluorescence imaging and establish the presence and integrity of the lipid bilayer by the successful insertion of α-Hemolysin transmembrane proteins. Finally, we show that the vesicle can be easily mechanically deformed, non-intrusively, by indenting the surface of the gel.
Photoresponsive materials feature properties that can be adjusted near- instantaneously, reversibly, and with high spatiotemporal precision, by light. There is considerable interest in maximising the degree of switching, and in measuring this degree during illumination in complex environments. We study the switching of photoresponsive lipid membranes that allow precise and reversible manipulation of membrane shape, permeability, and fluidity. Though these macroscopic photoresponses are clear, it is unclear how large the changes of trans/cis ratio are, and whether they can be improved. Here, we…
Protocellular energetics: Free energy estimates for all metabolic, self-assembly and vesicle fission processes
University of Southern Denmark (SDU)（南丹麦大学）；Santa Fe Institute (SFI)（圣塔菲研究所）；Donostia International Physics Center (DIPC)（圣塞巴斯蒂安国际物理中心）；Ikerbasque, Basque Foundation for Science（伊克拉巴斯科，巴斯克科学基金会）；Tohoku University（东北大学）；Department of Cellular, Computational and Integrative Biology (CIBIO) Trento（特伦托细胞、计算和整合生物学系）；Institute for Biochemistry, Greifswald University（格赖夫斯瓦尔德大学生物化学研究所）；Materials Physics Center (MFC)（材料物理中心）
On the lipid-bacterial protein interaction studied by quartz crystal microbalance with dissipation, transmission electron microscopy and atomic force microscopy
Direct measurement of DNA-mediated adhesion between lipid bilayers
可变形介观单元之间的多价相互作用在生物学中是普遍存在的，其中膜大分子介导相邻活细胞之间以及细胞与固体基质之间的相互作用。最近，类似的人工材料已经通过用选择性接头，特别是短DNA序列官能化顺应性布朗单元（例如乳液液滴和脂质囊泡）的外表面来合成。这一发展扩大了DNA作为选择性胶水的适用范围，最初适用于固体纳米和胶体颗粒。在非常可变形的脂质囊泡上，多价相互作用的统计效应和膜的机械变形之间的耦合引起复杂的涌现行为，正如我们最近所证明的[Parolini et al.，Nature Communications，2015，6，5948]。在这些系统中观察到的复杂现象学的几个方面仍然缺乏定量的实验表征和基本的理解。在这里，我们专注于DNA介导的多价相互作用的一个单一的脂质体粘附到一个平坦的支持双层。这种简化的几何形状使得能够估计由作用于脂质体的DNA介导的粘附力引起的膜张力。我们的实验研究完成了形态学测量和表征的DNA熔融过渡，探测原位福斯特共振能量转移光谱。实验结果进行了比较与分析理论的预测，耦合的囊泡的变形的移动连接器的统计力学的完整描述。最多只有一个拟合参数，我们的理论能够半定量地匹配实验数据，确认基本假设的质量。
We investigated the phase separation of dioleoylphosphatidylserine (DOPS) and dipalmitoylphosphatidylcholine (DPPC) in giant unilamellar vesicles in hypotonic solution using fluorescence and confocal laser scanning microscopy. Although phase separation in charged lipid membranes is generally suppressed by the electrostatic repulsion between the charged headgroups, osmotic stress can promote the formation of charged lipid domains. Interestingly, we observed three-phase coexistence even in DOPS/DPPC binary lipid mixtures. The three phases were DPPC-rich, dissociated DOPS-rich, and nondissociated…
Biophysical characterization of membrane phase transition profiles for the discrimination of Outer Membrane Vesicles (OMVs) from Escherichia coli grown at different temperatures
