Lee Jessica, Pir Cakmak Fatma, Booth Richard, Keating Christine D
Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA.
Small. 2024 Dec;20(52):e2406671. doi: 10.1002/smll.202406671. Epub 2024 Oct 14.
Prebiotically-plausible compartmentalization mechanisms include membrane vesicles formed by amphiphile self-assembly and coacervate droplets formed by liquid-liquid phase separation. Both types of structures form spontaneously and can be related to cellular compartmentalization motifs in today's living cells. As prebiotic compartments, they have complementary capabilities, with coacervates offering excellent solute accumulation and membranes providing superior boundaries. Herein, protocell models constructed by spontaneous encapsulation of coacervate droplets by mixed fatty acid/phospholipid and by purely fatty acid membranes are described. Coacervate-supported membranes form over a range of coacervate and lipid compositions, with membrane properties impacted by charge-charge interactions between coacervates and membranes. Vesicles formed by coacervate-templated membrane assembly exhibit profoundly different permeability than traditional fatty acid or blended fatty acid/phospholipid membranes without a coacervate interior, particularly in the presence of magnesium ions (Mg). While fatty acid and blended membrane vesicles are disrupted by the addition of Mg, the corresponding coacervate-supported membranes remain intact and impermeable to externally-added solutes. With the more robust membrane, fluorescein diacetate (FDA) hydrolysis, which is commonly used for cell viability assays, can be performed inside the protocell model due to the simple diffusion of FDA and then following with the coacervate-mediated abiotic hydrolysis to fluorescein.
具有益生元合理性的区室化机制包括两亲分子自组装形成的膜泡以及液-液相分离形成的凝聚滴。这两种结构都是自发形成的，并且可能与当今活细胞中的细胞区室化基序有关。作为益生元区室，它们具有互补的能力，凝聚滴具有出色的溶质积累能力，而膜则提供了更好的边界。本文描述了通过混合脂肪酸/磷脂自发包裹凝聚滴以及通过纯脂肪酸膜构建的原始细胞模型。凝聚滴支撑的膜在一系列凝聚滴和脂质组成范围内形成，膜的性质受凝聚滴与膜之间的电荷-电荷相互作用影响。由凝聚滴模板化膜组装形成的囊泡与没有凝聚滴内部的传统脂肪酸或混合脂肪酸/磷脂膜相比，具有截然不同的渗透性，特别是在存在镁离子（Mg）的情况下。虽然添加Mg会破坏脂肪酸和混合膜囊泡，但相应的凝聚滴支撑的膜保持完整，并且对外部添加的溶质不可渗透。由于具有更强健的膜，由于荧光素二乙酸酯（FDA）的简单扩散，然后通过凝聚滴介导的非生物水解为荧光素，因此可以在原始细胞模型内部进行常用于细胞活力测定的FDA水解。
