Comparative studies on the self-assembling behaviors of cationic and catanionic surfactant-like peptides

摘要

In order to introduce ionic bonds into traditional surfactant-like peptide to develop self-assembling materials with better properties, a catanionic surfactant-like peptide A_6K± was designed by removing the protecting {single bond}NH_2 at the C-terminus of the cationic surfactant-like peptide A_6K. Both TEM and AFM observations revealed that A_6K± could form longer nanofibers than A_6K did. On mica surface, A_6K could form membrane-like structures, which were likely formed by unassembled peptide monomers, while A_6K± only formed regular nanofibers, suggesting the absence of unassembled monomers. Pyrene probe spectrofluorometry showed that A_6K± had a much lower critical micelle concentration (CMC) than A_6K. The self-assembling structures of A_6K± were also more thermostable than those of A_6K and could endure temperature as high as 80 °C. Furthermore, changing the pH value to extreme acid or basic has more complicated effects on A_6K± than A_6K. These results indicated that the coexistence of opposite charges in the head group of A_6K± may help it to form nanostructures with better stability and pH-sensitivity, suggesting a novel approach to fabricate nanomaterials by catanionic surfactant-like peptides.