Novel Chimeric Amino Acid-Fatty Alcohol Ester Amphiphiles Self-Assemble into Stable Primitive Membranes in Diverse Geological Settings
Novel Chimeric Amino Acid-Fatty Alcohol Ester Amphiphiles Self-Assemble into Stable Primitive Membranes in Diverse Geological Settings
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DOI：
10.1089/ast.2022.0056
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发表时间：
2023-02-01
期刊：
影响因子：
4.2
通讯作者：
Sahai，Nita
中科院分区：
文献类型：
--
作者：
Namani，Trishool;Ruf，Reghan J.;Sahai，Nita
原始细胞被认为是具有最少代谢成分的自组装囊泡结构，能够在早期地球地质环境中自我维持和自我繁殖。生物分子（例如两亲物、肽和核酸或其前体）的共同进化和自组装对于原始细胞的出现至关重要。在这里，我们提出了一类新型的两亲物——氨基酸脂肪醇酯——它们在各种地球化学条件下自组装成稳定的原始膜隔室。甘氨酸辛酯（GOE）和异亮氨酸辛酯（IOE）是甘氨酸或异亮氨酸与辛醇（OcOH）的缩合酯产物，预计在温和的温度下通过湿-干循环形成。 GOE 在酸性水溶液 (pH 2–7) 中形成胶束，在中等 pH 值 (pH 7.3–8.2) 中形成囊泡。当与不同摩尔分数的辅助表面活性剂（辛酸 [OcA]、OcOH 或癸醇）混合时 [XCosurfactant= 0.1–0.5]，囊泡稳定性范围显着扩大，跨越极酸性至弱碱性 (pH 2–8) 和极碱性 (pH 10–11) 区域。只需少量的助表面活性剂[XCosurfactant= 0.1]即可形成稳定的囊泡结构。值得注意的是，这些基于 GOE 的囊泡在高浓度二价阳离子存在下也很稳定，即使在低 pH 值和模拟冥古宙海水成分（不含硫酸盐）中也是如此。为了更好地了解基于 GOE 的系统的自组装行为，我们为模拟酸性 pH 下的一系列混合 GOE/OcA 系统设计了互补的分子动力学计算机模拟。由此计算出的关键堆积参数值和自组装行为与我们的实验结果一致。 IOE 预计会表现出类似的自组装行为。因此，氨基酸-脂肪醇酯是一种由氨基酸头基和脂肪醇尾部组成的新型嵌合两亲物，可能有助于构建原始细胞膜，该膜在各种地球化学环境下保持稳定，有利于支持复制和自我维护。目前的工作有助于我们的工作主体支持我们对早期地球上（原始）生物分子的协同作用和共同进化的假设。
Primitive cells are believed to have been self-assembled vesicular structures with minimal metabolic components, that were capable of self-maintenance and self-propagation in early Earth geological settings. The coevolution and self-assembly of biomolecules, such as amphiphiles, peptides, and nucleic acids, or their precursors, were essential for protocell emergence. Here, we present a novel class of amphiphiles—amino acid-fatty alcohol esters—that self-assemble into stable primitive membrane compartments under a wide range of geochemical conditions. Glycinen-octyl ester (GOE) and isoleucinen-octyl ester (IOE), the condensation ester products of glycine or isoleucine with octanol (OcOH), are expected to form at a mild temperature by wet-dry cycles. The GOE forms micelles in acidic aqueous solutions (pH 2–7) and vesicles at intermediate pH (pH 7.3–8.2). When mixed with cosurfactants (octanoic acid [OcA]; OcOH, or decanol) in different mole fractions [XCosurfactant= 0.1–0.5], the vesicle stability range expands significantly to span the extremely acidic to mildly alkaline (pH 2–8) and extremely alkaline (pH 10–11) regions. Only a small mole fraction of cosurfactant [XCosurfactant= 0.1] is needed to make stable vesicular structures. Notably, these GOE-based vesicles are also stable in the presence of high concentrations of divalent cations, even at low pHs and in simulated Hadean seawater composition (without sulfate). To better understand the self-assembly behavior of GOE-based systems, we devised complementary molecular dynamics computer simulations for a series of mixed GOE/OcA systems under simulated acidic pHs. The resulting calculated critical packing parameter values and self-assembly behavior were consistent with our experimental findings. The IOE is expected to show similar self-assembly behavior. Thus, amino acid-fatty alcohol esters, a novel chimeric amphiphile class composed of an amino acid head group and a fatty alcohol tail, may have aided in building protocell membranes, which were stable in a wide variety of geochemical circumstances and were conducive to supporting replication and self-maintenance. The present work contributes to our body of work supporting our hypothesis for synergism and coevolution of (proto)biomolecules on early Earth.