In spite of extensive research, it remains a formidable challenge to control the dimension of the nanostructures self-assembled from short designed peptides. In this work, we show that peptide bolaamphiphiles form monolayer wall nanotubes, facilitated by the interplay between the side chain structure and hydrophobicity of the central residues. The peptide KI₄K self-assembles into nanotubes with a width of ∼100 nm, but changes in the molecular structure of amino acid side chains could hugely impact the nanostructures formed. The three variants of KI₄K, via the substitution of aromatic amino acids (F, Y, and Dopa) for the I residue closest to the C-terminus, could substantially reduce nanotube diameters, indicating a significant steric hindrance of the benzene rings on the lateral packing of β-sheets. However, the introduction of hydroxyl groups on the benzene rings alleviates the steric effect, with nanotube diameter increasing in the order of KI₃FK, KI₃YK, and KI₃DopaK, suggesting the formation of side chain H-bonds between β-sheets in addition to hydrophobic contacts. Because the self-assembly process of KI₃DopaK nanotubes is slow, key intermediates and their structural details are well characterized. With increasing incubation time, monolayered twisted ribbons and helical ribbons grow into mature KI₃DopaK nanotubes via the pitch closing route.

尽管进行了广泛的研究，但是控制短设计肽自组装的纳米结构的尺寸仍然是巨大的挑战。在这项工作中，我们表明肽boamphiphiles形成单层壁纳米管，由侧链结构和中心残基的疏水性之间的相互作用促进。肽KI ₄ K自组装成宽度约100 nm的纳米管，但是氨基酸侧链分子结构的变化会极大地影响所形成的纳米结构。KI ₄ K的三种变体，通过用芳族氨基酸（F，Y和Dopa）代替最接近C末端的I残基可显着减小纳米管直径，这表明苯环在β-折叠的侧向堆积上具有明显的空间位阻。然而，在苯环上引入羟基会减轻空间效应，纳米管直径按KI ₃ FK，KI ₃ YK和KI ₃ DopaK的顺序增加，表明在β-折叠之间形成侧链H键除了疏水接触。因为KI ₃的自组装过程DopaK纳米管速度较慢，关键中间体及其结构细节均已很好地表征。随着孵育时间的增加，单层扭曲带和螺旋带会通过节距闭合途径成长为成熟的KI ₃ DopaK纳米管。