科学家报告说，他们发现了一种可能在数亿年前让地球上的生命奇妙而专一地选择了所谓的左手氨基酸的“祖先夏娃”晶体。蛋白质的这些基本单元分为两种形式——左手和右手——就像互为镜像的一双手。他们的这项研究可能有助于解决生命起源的最令人困惑的谜题之一，该研究发表在了美国化学会的《晶体生长与设计》双月刊上。
Tu Lee 和Yu Kun Lin指出，原始地球的环境具有形成同等数量的左手和右手氨基酸的同等几率。然而，当最初的生命在30多亿年前形成的时候，蛋白质的所有氨基酸都是左手构造的。这种模式一直持续到了现代动植物。
这组科学家在实验室实验中使用左手和右手的天冬氨酸（一种氨基酸）的混合物研究了温度和其他条件如何影响了这种物质的晶体形成。他们发现在原始地球可能存在的条件下，左手天冬氨酸晶体可能在大尺度上很容易地形成。“天冬氨酸晶体然后确实能够成为单一的母晶体，也就是整个左手群体的祖先夏娃，”这篇文章说。(生物谷Bioon.com)
生物谷推荐原文出处：
Cryst. Growth Des. DOI: 10.1021/cg901219f
The Origin of Life and the Crystallization of Aspartic Acid in Water
Tu Lee* and Yu Kun Lin
Department of Chemical and Materials Engineering, National Central University, 300 Jhong-Da Road, Jhong-Li City 320, Taiwan, R.O.C.
The unusual molecular complexation of the enantiomers of aspartic acid in water was discovered and proven by a solubility test, solution freezing point, crystallization kinetics, and the incubation time change. The transformation of a “conglomerate solution” (CS) to a “racemic compound solution” (RCS) was dependent on both temperature and time. The CS was the solution phase which produced conglomerate crystals, and the RCS was the solution phase which gave a racemic compound. Fourier transformed infrared spectroscopy and powder X-ray diffraction were used to characterize aspartic acid solids crystallized from those complex solution phases and to distinguish conglomerate crystals from a racemic compound. We found that it took more than 36 h at 25 °C and 5 h at 45 °C just to complete the solution phase transformation of the CS of aspartic acid to the RCS of aspartic acid. However, the presence of an equimolar of succinic acid could hinder the solution phase transformation of the CS of aspartic acid to the RCS of aspartic acid for up to at least 8 h at 60 °C. This leeway of hours had provided an opportunity for the thermodynamically stable racemic aspartic acid to convert into the metastable conglomerate in water first by either a rapid acid?base reaction or the addition of an antisolvent with the temperature drop, without being concerned by its back conversion later to a racemic compound thermodynamically for quite some time. As a result, enantioseparation of aspartic acid by preferential crystallization in a large scale would have been very common and easy to occur on the primitive earth.
