Jacoby Guy, Cohen Keren, Barkan Kobi, Talmon Yeshayahu, Peer Dan, Beck Roy
The Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, Tel Aviv 6997801, Israel.
Laboratory of NanoMedicine, Department of Cell Research and Immunology, George S. Wise Faculty of Life Sciences, Department of Materials Sciences and Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 6997801, Israel.
Sci Rep. 2015 Mar 30;5:9481. doi: 10.1038/srep09481.
The metastable-to-stable phase-transition is commonly observed in many fields of science, as an uncontrolled independent process, highly sensitive to microscopic fluctuations. In particular, self-assembled lipid suspensions exhibit phase-transitions, where the underlying driving mechanisms and dynamics are not well understood. Here we describe a study of the phase-transition dynamics of lipid-based particles, consisting of mixtures of dilauroylphosphatidylethanolamine (DLPE) and dilauroylphosphatidylglycerol (DLPG), exhibiting a metastable liquid crystalline-to-stable crystalline phase transition upon cooling from 60°C to 37°C. Surprisingly, unlike classically described metastable-to-stable phase transitions, the manner in which recrystallization is delayed by tens of hours is robust, predetermined and controllable. Our results show that the delay time can be manipulated by changing lipid stoichiometry, changing solvent salinity, adding an ionophore, or performing consecutive phase-transitions. Moreover, the delay time distribution indicates a deterministic nature. We suggest that the non-stochastic physical mechanism responsible for the delayed recrystallization involves several rate-affecting processes, resulting in a controllable, non-independent metastability. A qualitative model is proposed to describe the structural reorganization during the phase transition.
亚稳态到稳态的相变在许多科学领域中普遍存在，是一个不受控制的独立过程，对微观涨落高度敏感。特别是，自组装脂质悬浮液会发生相变，但其潜在的驱动机制和动力学尚未得到很好的理解。在此，我们描述了一项关于脂质基颗粒相变动力学的研究，该颗粒由二月桂酰磷脂酰乙醇胺（DLPE）和二月桂酰磷脂酰甘油（DLPG）的混合物组成，在从60°C冷却至37°C时会发生亚稳态液晶到稳态晶体的相变。令人惊讶的是，与经典描述的亚稳态到稳态相变不同，重结晶延迟数十小时的方式是稳健的、预先确定的且可控的。我们的结果表明，可以通过改变脂质化学计量比、改变溶剂盐度、添加离子载体或进行连续相变来控制延迟时间。此外，延迟时间分布表明其具有确定性。我们认为，导致重结晶延迟的非随机物理机制涉及几个影响速率的过程，从而产生可控的、非独立的亚稳态。我们提出了一个定性模型来描述相变过程中的结构重组。
