Tolmachev Dmitry, Lukasheva Natalia, Mamistvalov George, Karttunen Mikko
Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoy pr. 31, 199004 St. Petersburg, Russia.
Faculty of Physics, St. Petersburg State University, Petrodvorets, 198504 St. Petersburg, Russia.
Polymers (Basel). 2020 Jun 3;12(6):1279. doi: 10.3390/polym12061279.
Investigation of the effect of CaCl salt on conformations of two anionic poly(amino acids) with different side chain lengths, poly-(α-l glutamic acid) (PGA) and poly-(α-l aspartic acid) (PASA), was performed by atomistic molecular dynamics (MD) simulations. The simulations were performed using both unbiased MD and the Hamiltonian replica exchange (HRE) method. The results show that at low CaCl concentration adsorption of Ca ions lead to a significant chain size reduction for both PGA and PASA. With the increase in concentration, the chains sizes partially recover due to electrostatic repulsion between the adsorbed Ca ions. Here, the side chain length becomes important. Due to the longer side chain and its ability to distance the charged groups with adsorbed ions from both each other and the backbone, PGA remains longer in the collapsed state as the CaCl concentration is increased. The analysis of the distribution of the mineral ions suggests that both poly(amino acids) should induce the formation of mineral with the same structure of the crystal cell.
通过原子分子动力学（MD）模拟研究了CaCl盐对两种具有不同侧链长度的阴离子聚氨基酸——聚（α-L-谷氨酸）（PGA）和聚（α-L-天冬氨酸）（PASA）构象的影响。模拟使用了无偏MD和哈密顿量副本交换（HRE）方法。结果表明，在低CaCl浓度下，Ca离子的吸附导致PGA和PASA的链尺寸显著减小。随着浓度的增加，由于吸附的Ca离子之间的静电排斥，链尺寸部分恢复。在此，侧链长度变得很重要。由于PGA的侧链较长，且其能够使吸附离子的带电基团相互之间以及与主链保持距离，随着CaCl浓度的增加，PGA在塌缩状态下保持更长。对矿物离子分布的分析表明，两种聚氨基酸都应诱导形成具有相同晶胞结构的矿物。
