氨基酸在绿脱石层间域内微观结构的分子动力学模拟

Molecular dynamics simulation of microstructure of amino acids in the interlayer space of nontronite

黏土矿物具有浓缩、保护和催化的功能,很可能在生命起源中发挥至关重要的作用。虽然大量研究关注氨基酸在富铝黏土矿物(如蒙脱石)表面的吸附和缩合反应,然而,富铁镁黏土矿物(如绿脱石)很可能广泛存在于早期地球,氨基酸在绿脱石表面的吸附和缩合反应研究却非常缺乏。本文使用分子动力学模拟手段,通过逐步减少水分子数量模拟脱水过程,研究脱水对氨基酸在绿脱石表面的吸附、有效反应对的形成和水化能等的影响。结果表明,氨基酸通过氨基与绿脱石表面氧形成氢键稳定地吸附在绿脱石表面,并在绿脱石表面形成有效反应对。脱水不仅有助于氨基酸在绿脱石表面的吸附和有效反应对的形成,而且还能降低体系的水化能,使体系在水化时释放更多能量。体系的水化能在热力学方面有利于肽键的形成,可能成为肽形成的驱动力。综上,绿脱石很可能对肽在早期地球的形成中起到关键作用。

Clay minerals are likely to have played significant roles in the origin of life due to their functions of concentration, protection, and catalysis. A large number of researches focusing on the adsorption and polymerization of amino acids onto the surface of Al-rich clay minerals(e.g. montmorillonite) have been undertaken. Though Fe-Mg rich clay minerals(e.g. nontronite) were likely to be widespread on the early Earth, there is a paucity of studies on the adsorption and polymerization of amino acids on the nontronite surface. The dehydration processes have been simulated by progressively reducing the number of water molecules using the molecular dynamics simulation method to investigate effects of dehydration on the adsorption of amino acids onto nontronite surface, formation of effective reactive pairs, hydration energy, etc. Results show that amino acids were stably adsorbed on the nontronite surface via hydrogen bonds between amino group and oxygen atoms of the nontronite surface and effective reactive pairs of amino acids were formed on the nontronite surface. The dehydration not only facilitated the adsorption and formation of effective reactive pairs of amino acids on the nontronite surface, but also was conducive to decrease hydration energy of the system, resulting in more energy releasing from the system during its hydration. The hydration energy of system was thermodynamically favorable to the formation of peptide bond, and likely to be the driving force of the peptide formation. In summary, nontronite was likely to have played key roles in the formation process of peptide on the early Earth.