Wu Eugene, Coppens Marc-Olivier, Garde Shekhar
Howard P. Isermann Department of Chemical and Biological Engineering and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute , Troy, New York 12180, United States.
Langmuir. 2015 Feb 10;31(5):1683-92. doi: 10.1021/la5043553. Epub 2015 Jan 28.
Arginine-rich proteins (e.g., lysozyme) or poly-L-arginine peptides have been suggested as solvating and dispersing agents for single-wall carbon nanotubes (CNTs) in water. In addition, protein structure-function in porous and hydrophobic materials is of broad interest. The amino acid residue, arginine (Arg(+)), has been implicated as an important mediator of protein/peptide-CNT interactions. To understand the structural and thermodynamic aspects of this interaction at the molecular level, we employ molecular dynamics (MD) simulations of the protein lysozyme in the interior of a CNT, as well as of free solutions of Arg(+) in the presence of a CNT. To dissect the Arg(+)-CNT interaction further, we also perform simulations of aqueous solutions of the guanidinium ion (Gdm(+)) and the norvaline (Nva) residue in the presence of a CNT. We show that the interactions of lysozyme with the CNT are mediated by the surface Arg(+) residues. The strong interaction of Arg(+) residue with the CNT is primarily driven by the favorable interactions of the Gdm(+) group with the CNT wall. The Gdm(+) group is not as well-hydrated on its flat sides, which binds to the CNT wall. This is consistent with a similar binding of Gdm(+) ions to a hydrophobic polymer. In contrast, the Nva residue, which lacks the Gdm(+) group, binds to the CNT weakly. We present details of the free energy of binding, molecular structure, and dynamics of these solutes on the CNT surface. Our results highlight the important role of Arg(+) residues in protein-CNT or protein-carbon-based material interactions. Such interactions could be manipulated precisely through protein engineering, thereby offering control over protein orientation and structure on CNTs, graphene, or other hydrophobic interfaces.
富含精氨酸的蛋白质（如溶菌酶）或聚-L-精氨酸肽被认为是单壁碳纳米管（CNT）在水中的溶剂化和分散剂。此外，蛋白质在多孔和疏水材料中的结构-功能受到广泛关注。氨基酸残基精氨酸（Arg(+)）被认为是蛋白质/肽与碳纳米管相互作用的重要介质。为了在分子水平上理解这种相互作用的结构和热力学方面，我们对碳纳米管内部的溶菌酶以及存在碳纳米管时精氨酸（Arg(+)）的自由溶液进行了分子动力学（MD）模拟。为了进一步剖析Arg(+)与碳纳米管的相互作用，我们还对存在碳纳米管时胍离子（Gdm(+)）和正缬氨酸（Nva）残基的水溶液进行了模拟。我们表明，溶菌酶与碳纳米管的相互作用是由表面的Arg(+)残基介导的。Arg(+)残基与碳纳米管的强烈相互作用主要是由Gdm(+)基团与碳纳米管壁的有利相互作用驱动的。Gdm(+)基团在其与碳纳米管壁结合的平坦面上水化程度较低。这与Gdm(+)离子与疏水聚合物的类似结合是一致的。相比之下，缺乏Gdm(+)基团的Nva残基与碳纳米管的结合较弱。我们展示了这些溶质在碳纳米管表面的结合自由能、分子结构和动力学的细节。我们的结果突出了Arg(+)残基在蛋白质-碳纳米管或蛋白质-碳基材料相互作用中的重要作用。这种相互作用可以通过蛋白质工程精确调控，从而实现对蛋白质在碳纳米管、石墨烯或其他疏水界面上的取向和结构的控制。
