Department of Earth Science, Graduate School of Science, Tohoku University, Sendai, Japan.
Astrobiology. 2011 Oct;11(8):799-813. doi: 10.1089/ast.2011.0637. Epub 2011 Sep 30.
The polymerization of amino acids leading to the formation of peptides and proteins is a significant problem for the origin of life. This problem stems from the instability of amino acids and the difficulty of their oligomerization in aqueous environments, such as seafloor hydrothermal systems. We investigated the stability of amino acids and their oligomerization reactions under high-temperature (180-400°C) and high-pressure (1.0-5.5 GPa) conditions, based on the hypothesis that the polymerization of amino acids occurred in marine sediments during diagenesis and metamorphism, at convergent margins on early Earth. Our results show that the amino acids glycine and alanine are stabilized by high pressure. Oligomers up to pentamers were formed, which has never been reported for alanine in the absence of a catalyst. The yields of peptides at a given temperature and reaction time were higher under higher-pressure conditions. Elemental, infrared, and isotopic analyses of the reaction products indicated that deamination is a key degradation process for amino acids and peptides under high-pressure conditions. A possible NH(3)-rich environment in marine sediments on early Earth may have further stabilized amino acids and peptides by inhibiting their deamination.
氨基酸的聚合导致肽和蛋白质的形成，这是生命起源的一个重大问题。这个问题源于氨基酸的不稳定性和它们在水相环境（如海底热液系统）中聚合的困难。我们根据氨基酸在成岩作用和变质作用期间在海洋沉积物中聚合的假说，在高温（180-400°C）和高压（1.0-5.5 GPa）条件下研究了氨基酸的稳定性及其聚合反应。我们的结果表明，甘氨酸和丙氨酸在高压下稳定。形成了寡聚物，最高可达五聚体，这在没有催化剂的情况下从未报道过丙氨酸的形成。在给定的温度和反应时间下，在较高压力条件下生成的肽的产率更高。反应产物的元素、红外和同位素分析表明，脱氨作用是氨基酸和肽在高压条件下的关键降解过程。早期地球上海洋沉积物中可能存在富含 NH3 的环境，通过抑制它们的脱氨作用，进一步稳定了氨基酸和肽。
