摘要
The life’s origin in submarine hydrothermal systems is a long-standing scenario supported by diverse scientific disciplines, while verification of its chemical plausibility remains a major bottleneck. Most scenarios of hydrothermal origin postulate peptides as key players in prebiotic chemistry; nevertheless, it remains unknown how peptides were formed from geochemically available amino acids that must be low in concentration. Here we show that a simple mixing with elemental sulfur (S0), hydrogen sulfide (HS–), and carbon monoxide (CO) enables an effective dimerization of glycine (Gly) at micro to several millimolar concentrations. Incubation of 1 mM Gly with the three inorganic compounds in a warm alkaline solution (pH 9.3 and 35 or 50 °C) led up to 18% conversion of Gly to glycylglycine (GlyGly). Dimerization of 0.01 mM Gly was also discerned in the yield far exceeding the thermodynamic equilibrium (0.4% yield). In this reaction, CO is oxidized to CO2 concomitant with the reduction of S0 to polysulfides, serving as the driving force for the Gly-to-GlyGly conversion. Although the formation of CO2 as a byproduct suppressed the formation of GlyGly, its adverse effect was mitigated by carbonate precipitation upon adding Mg2+ and Ca2+. To our knowledge, 0.01 mM is the lowest concentration of amino acid oligomerized experimentally in the prebiotic context. Given the ubiquity of S0, HS–, and CO in primordial ocean hydrothermal systems, and the abundance of Mg2+ and Ca2+ in seawater, our demonstrated favorable condition for amino acid dimerization is likely to have occurred on the Hadean seafloor. This possibility supports an abiotic appearance of peptides and thereby facilitates the hydrothermal origin of life.
摘要译文
生命在海底热液系统中的起源是多种科学学科支持的长期情况，而对其化学合理性的验证仍然是主要的瓶颈。水热来源的大多数情况都认为肽是益生元化学的关键参与者；然而，尚不清楚如何从必须低浓度的地球化学氨基酸形成肽。在这里我们表明，与元素硫（S 0 ），硫化氢（HS – ）和碳一氧化碳（CO）的简单混合可以有效地二聚甘氨酸（Glycine（Glycine））在微摩尔浓度至微摩尔浓度下。在温暖的碱性溶液（pH 9.3和35或50°C）中与三种无机化合物一起孵育1 mM，导致Gly转化为甘油甘氨酸（Glygly）的18％。还辨别出0.01 mM gly的二聚化在产量中远远超过热力学平衡（0.4％的产率）。在此反应中，将CO氧化为CO 2伴随着S 0 对多硫化物的还原，这是Gly-Gly-GlyGly conversion依的驱动力。尽管CO 2作为副产品的形成抑制了甘油的形成，但在添加Mg 2+和Ca 2+时，通过碳酸盐沉淀来减轻其不良影响。据我们所知，0.01 mM是在益生元背景下实验中氨基酸寡聚的最低浓度。给定S 0 ，hs – 和CO在原始海洋热液系统中的无处不在，以及Mg 2+和ca 2+在海水中，我们证明的对氨基酸二聚的有利状况可能发生在哈迪斯海底。这种可能性支持肽的非生物外观，从而促进了生命的热液起源。
Norio Kitadai; Shigeru Shimamura; Wataru Takahagi; Masayuki Miyazaki; ... Satoshi Okada. Elemental sulfur, hydrogen sulfide, and carbon monoxide-driven dimerization of glycine at sub-millimolar concentrations: Implications for the origin of life[J]. Geochimica et Cosmochimica Acta, 2023,349: 55-63