Salts Responsive Nanovesicles Through <I>π</I>-Stacking Induced Self-Assembly of Backbone Modified Tripeptides
作者:Pradyot Koley、Michael G. B. Drew、Animesh Pramanik
DOI:10.1166/jnn.2011.4219
日期:2011.8.1
A set of backbone modified peptides of general formula Boc-Xx-m-ABA-Yy-OMe where m-ABA is meta-aminobenzoic acid and Xx and Yy are natural amino acids such as Phe, Gly, Pro, Leu, Ile, Tyr and Trp etc., are found to self-assemble into soft nanovesicular structures in methanol-water solution (9:1 by v/v). At higher concentration the peptides generate larger vesicles which are formed through fusion of smaller vesicles. The formation of vesicles has been facilitated through the participation of various noncovalent interactions such as aromatic π-stacking, hydrogen bonding and hydrophobic interactions. Model study indicates that the π-stacking induced self-assembly, mediated by m-ABA is essential for well structured vesicles formation. The presence of conformationally rigid m-ABA in the backbone of the peptides also helps to form vesicular structures by restricting the conformational entropy. The vesicular structures get disrupted in presence of various salts such as KCl, CaCl2, N(n-Bu4)Br and (NH4)2SO4 in methanol-water solution. Fluorescence microscopy and UV studies reveal that the soft nanovesicles encapsulate organic dye molecules such as Rhodamine B and Acridine Orange which could be released through salts induced disruption of vesicles.
一组通式为 Boc-Xx-m-ABA-Yy-OMe 的骨架修饰肽(其中 m-ABA 为偏氨基苯甲酸,Xx 和 Yy 为天然氨基酸,如 Phe、Gly、Pro、Leu、Ile、Tyr 和 Trp 等)在甲醇-水溶液(体积比为 9:1)中可自组装成柔软的纳米囊泡结构。当浓度较高时,肽会产生较大的囊泡,这些囊泡是由较小的囊泡融合而成的。通过各种非共价相互作用,如芳香π堆积、氢键和疏水相互作用,促进了囊泡的形成。模型研究表明,由 m-ABA 介导的π堆积诱导的自组装对结构良好的囊泡的形成至关重要。多肽骨架中存在构象刚性 m-ABA,也有助于通过限制构象熵形成囊泡结构。在甲醇-水溶液中,当存在 KCl、CaCl2、N(n-Bu4)Br 和 (NH4)2SO4 等各种盐类时,囊泡结构会被破坏。荧光显微镜和紫外线研究表明,软纳米囊泡包裹着罗丹明 B 和吖啶橙等有机染料分子,这些分子可通过盐引起的囊泡破坏释放出来。