Dipartimento di Agrobiologia ed Agrochimica, Università della Tuscia, Via San Camillo De Lellis, 01100 Viterbo, Italy.
Phys Life Rev. 2012 Mar;9(1):84-104. doi: 10.1016/j.plrev.2011.12.002. Epub 2011 Dec 13.
The complexity of life boils down to the definition: "self-sustained chemical system capable of undergoing Darwinian evolution" (Joyce, 1994) [1]. The term "self-sustained" implies a set of chemical reactions capable of harnessing energy from the environment, using it to carry out programmed anabolic and catabolic functions. We briefly present our opinion on the general validity of this definition. Running anabolic and catabolic functions entails complex chemical information whose stability, reproducibility and evolution constitute the core of what is dubbed genetics. Life as-we-know-it is made of the intimate interaction of metabolism and genetics, both built around the chemistry of the most common elements of the Universe (hydrogen, oxygen, nitrogen, carbon). Other elements like phosphorus and sulphur play important but ancillary and potentially replaceable roles. The reproducible interaction of metabolic and genetic cycles results in the hypercycles of organization and de-organization of chemical information that we consider living entities. In order to approach the problem of the origin of life it is therefore reasonable to start from the assumption that both metabolism and genetics had a common origin, shared a common chemical frame, were embedded in physical-chemical conditions favourable for the onset of both. The most abundant three-atoms organic compound in interstellar environment is hydrogen cyanide HCN, the most abundant three-atoms inorganic compound is water H(2)O. The combination of the two results in the formation of formamide H(2)NCOH. We have explored the chemistry of formamide in conditions compatible with the synthesis and the stability of compounds of potential pre-genetic and pre-metabolic interest. We discuss evidence showing (i) that all the compounds necessary for the build-up of nucleic acids are easily obtained abiotically, (ii) that essentially all the steps leading to the spontaneous generation of RNA are abiotically possible, (iii) that the key compounds of extant metabolic cycles are obtained in the same chemical frame, often in the same test tube. How close are these observations to a plausible scenario for the origin of life?
“能够进行达尔文式进化的自维持化学系统”（Joyce，1994）[1]。“自维持”一词意味着一组能够从环境中获取能量并利用能量进行有计划的合成代谢和分解代谢功能的化学反应。我们简要地提出了我们对这个定义的普遍有效性的看法。进行合成代谢和分解代谢功能需要复杂的化学信息，其稳定性、可重复性和进化构成了所谓遗传学的核心。我们所知道的生命是由代谢和遗传的紧密相互作用构成的，这两者都围绕着宇宙中最常见元素（氢、氧、氮、碳）的化学构建。其他元素，如磷和硫，虽然发挥着重要作用，但只是辅助性的，而且可能是可替代的。代谢和遗传循环的可重复相互作用导致了化学信息的超循环组织和去组织，我们认为这就是生命实体。因此，为了研究生命起源的问题，从以下假设出发是合理的：代谢和遗传具有共同的起源，共享共同的化学框架，并且嵌入在有利于两者同时发生的物理化学条件中。星际环境中最丰富的三原子有机化合物是氢氰酸 HCN，最丰富的三原子无机化合物是水 H(2)O。两者的结合导致形成甲酰胺 H(2)NCOH。我们已经探索了在与潜在前遗传和前代谢化合物的合成和稳定性兼容的条件下的甲酰胺化学。我们讨论了以下证据：（i）所有用于构建核酸的必需化合物都可以很容易地非生物合成获得，（ii）基本上所有导致 RNA 自发生成的步骤都可以非生物地进行，（iii）现存代谢循环的关键化合物都是在相同的化学框架中获得的，通常在同一个试管中获得。这些观察结果与生命起源的合理场景有多接近？
