Zhu Chang, Wang Qian, Huang Xiaoxiao, Yun Jiena, Hu Qiaoli, Yang Gang
College of Resources and Environment & Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, Southwest University, Chongqing, 400715, China.
College of Resources and Environment & Chongqing Key Laboratory of Soil Multi-scale Interfacial Process, Southwest University, Chongqing, 400715, China.
Colloids Surf B Biointerfaces. 2019 Nov 1;183:110458. doi: 10.1016/j.colsurfb.2019.110458. Epub 2019 Aug 26.
Almost all clay minerals carry an abundance of surface charges. The role and impacts of surface charges during adsorption of amino acids and biochemical reactions are of great importance while currently remain elusive, which are to be tackled in this study by first-principles density functional calculations. A wide range of surface charges (-0.42˜ + 0.42 C m) have been considered. Distribution of different amino acid isomers and their interaction with clay minerals rely strongly on the sign and amount of surface charges. Zwitterionic structures remain stable for all negative surface charges and become dominant when negative surface charges are abundant (σ ≤ -0.28 C m), whereas only very high positive surface charges (σ ≥ +0.35 C m) can stabilize zwitterionic glycine. Increase of surface charges pronouncedly enhances the interactions of amino acids with clay minerals, which favors their gathering at clay surfaces and condensation to protein fragments. The superior binding of amino acids by negatively rather than positively charged clay minerals is due to stronger H bonding and electrostatic interactions. The biochemical reactions are greatly accelerated at higher surface charges and zwitterion formation becomes almost barrierless; however, the reverse reactions of forming canonical isomers have so moderate activation barriers that can occur facilely and get ready for the condensation to protein fragments. Accordingly, clay minerals, even in the anhydrous state, should be the suitable birthplace for life, where surface charges play a central role.
几乎所有的黏土矿物都带有大量的表面电荷。表面电荷在氨基酸吸附和生化反应过程中的作用及影响至关重要，但目前仍不清楚，本研究将通过第一性原理密度泛函计算来解决这些问题。研究考虑了广泛的表面电荷范围（-0.42˜+0.42 C m）。不同氨基酸异构体的分布及其与黏土矿物的相互作用强烈依赖于表面电荷的符号和数量。两性离子结构在所有负表面电荷情况下都保持稳定，并且当负表面电荷丰富时（σ≤-0.28 C m）占主导地位，而只有非常高的正表面电荷（σ≥+0.35 C m）才能使两性离子甘氨酸稳定。表面电荷的增加显著增强了氨基酸与黏土矿物的相互作用，这有利于它们在黏土表面聚集并缩合形成蛋白质片段。带负电荷的黏土矿物对氨基酸的结合能力优于带正电荷的黏土矿物，这是由于更强的氢键和静电相互作用。在较高的表面电荷下，生化反应大大加速，两性离子的形成几乎没有障碍；然而，形成标准异构体的逆反应具有适度的活化能垒，能够轻易发生并为缩合形成蛋白质片段做好准备。因此，黏土矿物即使在无水状态下也应该是生命诞生的合适场所，表面电荷在其中起着核心作用。
