Mineral Surface-Mediated Processes in Protocell Evolution: Membrane Self-Assembly and Emergence of Energy Transduction

(1)技术摘要我们提出，地球化学水环境化学起着重要的作用，在选择脂质膜组成是稳定的（适者生存的原始细胞）。我们将使用由单链、多组分两亲性囊泡组成的模型“原始细胞”作为生物膜形成脂质的益生元类似物。我们将确定哪种混合的两亲物组合物在变化的环境溶液条件下是稳定的。存活的囊泡群体将通过荧光测定法和紫外-可见光谱法进行定量鉴定，并通过高压液相色谱法确定最合适的两亲物浓度。这些囊泡组合物将被认为是“最合适的”。“将在广泛的溶液pH值范围内以及在不存在或存在溶解盐（NaCl、KCl、NaBr、CaCl 2、MgCl 2、MgSO 4，各浓度为0.01和0.1 M）的情况下检查囊泡稳定性。对于较少数量的样品，我们还将研究囊泡稳定性的温度依赖性。这些条件将代表广泛的地球化学环境，如淡水、碱性或酸性湖水、潮间带水和海水。这些结果将对确定哪些地球化学环境会为适者生存的原始细胞提供选择压力产生影响。(2)更广泛的意义这个项目旨在了解生命进化的一个关键方面，即弄清楚细胞，生命的基石，是如何存在的。 细胞的一个基本和关键组成部分是它们的膜，它包裹着它们所有的内容物。 这些膜是由脂质构成的。 在地球的历史上，是什么导致了稳定的脂质膜的形成是未知的。 这项研究试图通过检查生物膜形成脂质类似物在代表不同自然环境的条件下的行为来解决这个谜团。 特别是，本研究将探讨矿物表面在脂质形成“原始细胞”中的作用。除了本项目对生命起源的影响外，增加我们对矿物和脂质膜之间相互作用的基本理解对医学地质学、纳米医学和纳米技术的健康/安全也有影响。

(1) Technical abstractWe propose that geochemical aqueous environment chemistry played an important role in selecting lipid membrane compositions that were stable (survival of the fittest protocells). We will use model "protocells" consisting of single-chain, multi-component amphiphile vesicles as a prebiotic analog to biological membrane-forming lipids. We will determine which mixed amphiphile compositions are stable under changing environmental solution conditions. Surviving vesicle populations will be quantitatively identified by fluorometry and UV-Vis spectroscopy and fittest amphiphile concentrations will be determined by high-pressure liquid chromatography. These vesicle compositions will be considered as the "fittest." Vesicle stability will be examined for a wide range of solution pHs and in the absence or presence of dissolved salts (NaCl, KCl, NaBr, CaCl2, MgCl2, MgSO4, each at 0.01 and 0.1M concentrations). For a smaller number of samples, we will also examine the temperature-dependence of vesicle stability. These conditions will represent a wide range of geochemical environments, such as freshwater, alkaline or acidic lake water, intertidal zone water and seawater. Results will have implications for determining which geochemical environments would have provided a selection pressure for survival of the fittest protocells.(2) Broader significance This project aims to understand a critical aspect of the evolution of life, namely in figuring out how cells, the building blocks of life, came to exist. An essential and critical component of cells is their membranes, which encase all of their contents. These membranes are made of lipids. In the history of the Earth, it is unknown what led to the formation of stable lipid membranes. This research seeks to address this mystery by examining the behavior of analogs to biological membrane-forming lipids under conditions that represent different natural environments. In particular, this study will examine the role that mineral surfaces can play in the formation of "protocells" from lipids.In addition to this project's implications for the origin of life, increasing our fundamental understanding of the interaction between minerals and lipid membranes has implications for medical geology, nanomedicine, and the health/safety of nanotechnology.