School of Mathematics and Physics, University of Lincoln, Brayford Pool, Lincoln LN6 7TS, United Kingdom.
School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen, Germany.
J Chem Phys. 2017 Feb 21;146(7):074703. doi: 10.1063/1.4975689.
Peptides are versatile molecules with applications spanning from biotechnology to nanomedicine. They exhibit a good capability to unbundle carbon nanotubes (CNT) by improving their solubility in water. Furthermore, they are a powerful drug delivery system since they can easily be uptaken by living cells, and their high surface-to-volume ratio facilitates the adsorption of molecules of different natures. Therefore, understanding the interaction mechanism between peptides and CNT is important for designing novel therapeutical agents. In this paper, the mechanisms of the adsorption of antimicrobial peptide Cecropin A-Magainin 2 (CA-MA) on a graphene nanosheet (GNS) and on an ultra-short single-walled CNT are characterized using molecular dynamics simulations. The results show that the peptide coats both GNS and CNT surfaces through preferential contacts with aromatic side chains. The peptide packs compactly on the carbon surfaces where the polar and functionalizable Lys side chains protrude into the bulk solvent. It is shown that the adsorption is strongly correlated to the loss of the peptide helical structure. In the case of the CNT, the outer surface is significantly more accessible for adsorption. Nevertheless when the outer surface is already covered by other peptides, a spontaneous diffusion, via the amidated C-terminus into the interior of the CNT, was observed within 150 ns of simulation time. We found that this spontaneous insertion into the CNT interior can be controlled by the polarity of the entrance rim. For the positively charged CA-MA peptide studied, hydrogenated and fluorinated rims, respectively, hinder and promote the insertion.
肽是一种多功能分子，其应用范围从生物技术到纳米医学。它们通过提高在水中的溶解度，表现出很好的解开碳纳米管（CNT）的能力。此外，它们还是一种强大的药物输送系统，因为它们可以很容易地被活细胞吸收，并且它们的高表面积与体积比有利于不同性质的分子的吸附。因此，了解肽与 CNT 之间的相互作用机制对于设计新型治疗剂非常重要。在本文中，使用分子动力学模拟研究了抗菌肽 Cecropin A-Magainin 2（CA-MA）在石墨烯纳米片（GNS）和超短单壁 CNT 上吸附的机制。结果表明，肽通过与芳族侧链的优先接触，在 GNS 和 CNT 表面上覆盖。肽在碳表面上紧密堆积，其中极性和可功能化的赖氨酸侧链突出到主体溶剂中。结果表明，吸附与肽螺旋结构的丧失密切相关。在 CNT 的情况下，外表面更便于吸附。然而，当外表面已经被其他肽覆盖时，在 150 ns 的模拟时间内，通过酰胺化的 C 末端自发扩散到 CNT 的内部观察到了这一现象。我们发现，这种自发插入 CNT 内部的行为可以通过入口边缘的极性来控制。对于研究的带正电荷的 CA-MA 肽，氢化和氟化边缘分别阻碍和促进了插入。
