物理化学学报 >> 2021, Vol. 37 >> Issue (10): 2002021.doi: 10.3866/PKU.WHXB202002021

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咪唑类离子液体与酪氨酸相互作用及机理的密度泛函理论研究

吴智伟1,2, 丁伟璐1, 张雅琴1, 王艳磊1, 何宏艳1,3,*()   

  1. 1 中国科学院过程工程研究所离子液体清洁过程北京市重点实验室,北京 100190
    2 中国科学院大学中丹学院,北京 100049
    3 郑州中科新兴产业技术研究院,郑州 450000
  • 收稿日期:2020-02-19 录用日期:2020-04-06 发布日期:2020-04-10
  • 通讯作者: 何宏艳 E-mail:hyhe@ipe.ac.cn
  • 基金资助:
    国家自然科学基金优秀青年科学基金(21922813);国家自然科学基金重点项目(21834006);国家自然科学基金面上项目(21978027);中国科学院前沿科学重点研究计划(QYZDB-SSW-SLH022);中国科学院青年创新促进会(2017066)

Interaction and Mechanism between Imidazolium Ionic Liquids and the Zwitterionic Amino Acid Tyr: a DFT Study

Zhiwei Wu1,2, Weilu Ding1, Yaqin Zhang1, Yanlei Wang1, Hongyan He1,3,*()   

  1. 1 Beijing Key Laboratory of Ionic Liquids Clean Process, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
    2 Sino-Danish College, University of Chinese Academy of Sciences, Beijing 100049, China
    3 Zhengzhou Institute of Emerging Industrial Technology, Zhengzhou 450000, China
  • Received:2020-02-19 Accepted:2020-04-06 Published:2020-04-10
  • Contact: Hongyan He E-mail:hyhe@ipe.ac.cn
  • About author:Hongyan He, Email: hyhe@ipe.ac.cn; Tel.: +86-10-82544875
  • Supported by:
    the National Science Fund for Excellent Young Scholars, China(21922813);Key Program of National Natural Science Foundation of China(21834006);General program of National Natural Science Foundation of China(21978027);Key Research Program of Frontier Sciences of CAS(QYZDB-SSW-SLH022);Youth Innovation Promotion Association of CAS(2017066)

摘要:

离子液体的物理化学性质稳定且结构可调,被认为是潜在的新一代绿色高效生物分子溶剂。本文通过密度泛函理论研究了系列咪唑基离子液体与两性离子型氨基酸(酪氨酸)的相互作用及机理。利用对称微扰理论(SAPT)、分子中的原子理论(AIM)及约化密度梯度函数(RDG),分析了氢键作用、静电力、诱导力和色散力对离子液体-氨基酸体系相互作用的贡献。计算结果表明静电作用对于阴、阳离子与酪氨酸的相互作用占主导地位。对于系列阳离子而言,具有不同的甲基取代位点和烷基侧链长度对不同的相互作用模式会产生显著影响。其中,当甲基位于咪唑环的C2位点时,诱导力与色散力占比差别较小;当甲基取代位于咪唑环的N3位点时,诱导力与色散力占比差别较大。产生这一差异的原因在于当甲基位于C2位时,氢键、咪唑环与苯环之间的π+-π作用为主要作用模式,而甲基取代位为N3位时,氢键和烷基链与苯环之间的CAlkyl-H…π作用则成为主导。进一步获得离子对-酪氨酸的相互作用能变化趋势与阳离子-酪氨酸的变化趋势一致,阴阳离子的共同作用使其与酪氨酸结合更稳定。该研究结果阐明了离子液体中阳离子氢键位点及侧链长度差异对于离子液体-酪氨酸体系的相互作用模式的影响机制,为高效分离氨基酸的功能性离子液体的设计和筛选提供了新思路。

关键词: 离子液体, 两性离子型氨基酸, 相互作用机理, 氢键作用, 范德华相互作用

Abstract:

Ionic liquids (ILs) are thermally and chemically stable and have adjustable structures, which gives them the potential to be used as green, efficient biomolecular solvents. Given the critical role of ILs in dissolving biomolecules, the mechanism of interaction between them deserves further study. Herein, density functional theory (DFT) calculations, using the SMD implicit water solvent model, were employed to study the interaction and mechanism between a hydrophobic zwitterionic amino acid (Tyr) and a series of imidazolium ILs with different alkyl chain lengths and methylation sites. The contributions of hydrogen bonding (H-bonding), electrostatic effects, induction, and dispersion to the intermolecular interactions were determined by combining the symmetry-adapted perturbation theory (SAPT), the atoms in molecules (AIM) theory, and reduced density gradient (RDG) analysis. The results indicate that the H-bonding between the IL cation and Tyr is stronger than that between the IL anion and Tyr; however, the binding between either ion and Tyr is dominated by electrostatic effects. By contrast, the difference between the induction and dispersion forces is small when methylation occurs on the C2 site of the imidazolium cation; whereas, it is significantly large when methylation takes place on the N3 site. This is rationalized by the interaction patterns that vary based on the methylation site. H-bonding and π+-π stacking interactions between the imidazole and benzene rings are dominant during C2-methylation, while H-bonding and CAlkyl-H…π interactions between the alkyl chain and benzene ring are dominant during N3-methylation. Increasing the side alkyl chain length has different effects on the interaction energy to cations with different methylation sites. During N3-methylation, when the side alkyl chain length increases from 4 to 12, there are significant van der Waals interactions between the Tyr benzene and the side alkyl chain. However, these van der Waals interactions are inapparent when methylation takes place on the C2 site. Finally, the synergetic effect of the H-bonding and the interaction between the benzene and the side alkyl chain for C2-methylation is greater than the H-bonding and the interaction between the imidazole and benzene rings for N3-methylation, when the side alkyl chain length n > 9. Therefore, the interaction strength and mechanism in these imidazolium-Tyr complexes can be regulated by changing the methylation site and the side alkyl chain length of the cation. Further study of ion-pair and Tyr reveals that the change tendency of the interaction energy of IL-Tyr systems is consistent with that of cation-Tyr cases, and the ion pair further stabilizes the binding with Tyr. These results illustrate the interaction mechanism of IL-Tyr systems and provide a novel strategy for the design and screening of functional ILs for amino acid extraction and separation in the future.

Key words: Ionic liquids, Zwitterionic amino acid, Interaction and mechanism, Hydrogen bond effect, Van der Waals effect

MSC2000: 

  • O641