生命起源的化学演化假设

A Hypothesis of Chemical Evolution of the Origin of Life

摘要: 在佛克斯的模拟实验上，氨基酸能发生聚合，生成一种类似蛋白质的高聚合物，这类高聚合物在水溶液中能够自动聚集成小球状的多分子体系，称之为微球体。微球体具有界膜和一定的内部结构，并能通过分裂的方式增殖，曾被认作是原始生命的雏形。模拟实验形成的类蛋白分子具有一定的多维空间结构和微弱的催化作用，但因不是模板合成，不能复制，其构成的微球体缺乏生命的基本特征—新陈代谢和自我繁殖，此模拟实验碰到了死结。生命的基本特征是新陈代谢和自我繁殖，实现这一过程是核酸与蛋白质共同作用的复杂化学反应，此复杂化学反应如何在原始地球环境出现仍是未解之谜。模拟实验中的微球体具有一个特征，即能不断地从溶液中吸收进类蛋白分子，弥补其内的类蛋白分子的水解，只要溶液中有足够的类蛋白分子的供应，微球体就能长期保存。微球体的这一特征符合耗散结构，在对类蛋白分子的“耗散”中，自发发生了由类蛋白分子自身多维空间结构的复杂有序程度相对差异所引起的留存性选择(分子选择)，即分子量较大、具有相对复杂的多维空间结构的类蛋白分子较稳定及寿命较长，在自然水解中更易被保留，微球体也会因构成它的类蛋白分子相对复杂和有序，使其有序化、组织化和稳定化，会在一定程度上发生自组织。无独有偶，大分子的催化功能由其多维空间结构的状态决定，微球体通过“耗散”作用和分子选择，保留下来的正是这样的类蛋白分子。微球体可能因组成分子有相对较高的催化活性，使得在原始地球的热泉或海洋里难于自然发生的很多复杂的化学反应能在其内发生。在某些微球体内可能发生了与有机物分解相偶联的核苷酸生成的能量连锁反应，核苷酸可能进一步聚合生成核糖核酸和氨基酰–核糖核酸，并最终发生了以核糖核酸为模板，以氨基酰–核糖核酸为氨基供体，类蛋白质催化(或核糖核酸参与催化)的真正蛋白质合成，新陈代谢的基本内容形成，这样的微球体发生质变，原始生命也就诞生。微球体具有耗散结构特征，在对溶液中类蛋白分子的“耗散”过程中，发生了由类蛋白分子自身多维空间结构的复杂有序程度相对差异所引起的留存性选择，将使其有序化并发生自组织，这是微球体向原始生命演化的自发过程，并最终将导致原始生命的产生。

Abstract: The microspheres constituted by proteinoids synthesized from Fox’s simulation experiments. They had peptide bond structure and weak catalysis, as well as proliferated themselves. Such mi-crospheres were believed the models for primitive life. Due to lack of metabolism and self-reproduction, the microspheres could not meet requirements of life. Thus, how microspheres could evolve into primitive life remained unsolved mysteries. The microspheres were supposed a dissipative structure and the processes of absorption and hydrolysis could be balanced to maintain their stability by consuming proteinoid. Proteinoid molecules differed in their life spans, which were mainly determined by their multi-space structures. Consequently, molecule selection and retention could occur spontaneously in microspheres and lead to a more organized and stabilized structure of the whole microsphere with time through dissipative process. More complex chain network of chemical reactions could happen in microspheres because the proteinoid with complex, ordered multi-space structure and relatively high catalytic activity would retain. In such microspheres, nucleotides could produce and further aggregate into RNA. The synthesis of real proteins could take place with RNA as the template catalyzed by proteinoids or RNA inside micro-spheres. When template-based protein molecules replaced the proteinoid inside the microspheres, a protein-based self-catalyzed network of chemical reactions could take place. It is plausible if Fox’s proteinoids microspheres are to dawn on a dissipative structure, then molecule selection could occur spontaneously by “dissipative” proteinoids, and the microspheres would acquire catalytic activity due to preserving the proteinoid with a large molecular weight and relatively complex and ordered multi-space structure, and relatively high catalytic activity. Thus the microspheres would spontaneously go to self-organizing, and evolve into primitive life.