Department of Chemistry and Biochemistry and CIRES, University of Colorado, Boulder, Colorado 80309, USA.
Acc Chem Res. 2012 Dec 18;45(12):2106-13. doi: 10.1021/ar300027q. Epub 2012 Apr 17.
The prebiotic conversion of simple organic molecules into complex biopolymers necessary for life can only have emerged on a stage set by geophysics. The transition between "prebiotic soup," the diverse mixture of small molecules, and complex, self-replicating organisms requires passing through the bottleneck of fundamental chemistry. In this Account, we examine how water-air interfaces, namely, the surfaces of lakes, oceans, and atmospheric aerosols on ancient Earth, facilitated the emergence of complex structures necessary for life. Aerosols are liquid or solid suspensions in air with a broad, power law size distribution. Collectively, these globally distributed atmospheric particles have an enormous surface area. Organic films at the interface between water and air offer advantages for biomolecular synthesis compared with the bulk and can simultaneously participate in the folding of biopolymers into primitive enclosed structures. We survey the advantages of the water-air interface for prebiotic chemistry in a geophysical context from three points of view. We examine the formation of biopolymers from simple organic precursors and describe the necessity and availability of enclosures. In addition, we provide a statistical mechanical approach to natural selection and emergence of complexity that proposes a link between these molecular mechanisms and macroscopic scales. Very large aerosol populations were ubiquitous on ancient Earth, and the surfaces of lakes, oceans, and atmospheric aerosols would have provided an auspicious environment for the emergence of complex structures necessary for life. These prebiotic reactors would inevitably have incorporated the products of chemistry into their anhydrous, two-dimensional organic films in the three-dimensional fluids of the gaseous atmosphere and the liquid ocean. The untrammeled operation of natural selection on these aerosols provided the likely location where condensation reactions could form biopolymers by elimination of water. The fluctuating exposure of the large, recycling aerosol populations to radiation, pressure, temperature, and humidity over geological time allows complexity to emerge from simple molecular precursors. We propose an approach that connects chemical statistical thermodynamics and the macroscopic world of the planetary ocean and atmosphere.
前生物将简单的有机分子转化为生命所必需的复杂生物聚合物的转化只能在地球物理学设定的舞台上出现。从“前生物汤”（小分子的各种混合物）到复杂的自我复制生物的转变，需要通过基础化学的瓶颈。在本报告中，我们研究了水-气界面（即古代地球湖泊、海洋和大气气溶胶的表面）如何促进生命所需复杂结构的出现。气溶胶是空气中的液体或固体悬浮液，具有广泛的幂律尺寸分布。这些在全球范围内分布的大气颗粒具有巨大的表面积。与体相相比，水-气界面上的有机膜有利于生物分子合成，并且可以同时参与生物聚合物折叠成原始封闭结构。我们从三个角度考察了地球物理背景下水-气界面在前生物化学中的优势。我们检查了从简单的有机前体形成生物聚合物，并描述了封闭的必要性和可用性。此外，我们提供了一种统计力学方法来研究自然选择和复杂性的出现，该方法提出了这些分子机制与宏观尺度之间的联系。在古代地球上，非常大的气溶胶种群无处不在，而湖泊、海洋和大气气溶胶的表面将为生命所必需的复杂结构的出现提供有利的环境。这些前生物反应器将不可避免地将化学产物纳入其无水二维有机薄膜中，这些有机薄膜存在于气态大气和液态海洋的三维流体中。自然选择在这些气溶胶上的不受限制的运作提供了可能的位置，其中缩合反应可以通过消除水来形成生物聚合物。在地质时间内，大量、可回收的气溶胶种群对辐射、压力、温度和湿度的波动暴露允许从简单的分子前体中出现复杂性。我们提出了一种将化学统计热力学与行星海洋和大气的宏观世界联系起来的方法。
