Fabrication of nucleobase-functionalized supramolecular nanofiber through peptide self-assembly

In this study, we describe a novel molecular self-assembling system of a nucleobase-functionalized oligopeptide. An adenine-terminated amphiphilic triblock peptide (1), which consists of hydrophobic Leu and hydrophilic Lys, was newly synthesized as a building block for self-assembly. The conformational and self-assembling properties of 1 in water at various conditions were examined by means of circular dichroism, FTIR, UV, atomic force microscopy, and transmission electron microscopy measurements. The experimental results revealed that the peptide 1 self-assembled into beta-sheet nanofiber under certain conditions, in which the nucleobase moieties were stacked with each other. The nanofiber possessed a diameter of ca. 6 nm and clearly visible left-handed twist with a periodicity of ca. 50 nm. Such secondary and quaternary structures of 1 could be easily controlled by manipulating the solution pH. Furthermore, the addition of complemental nucleoside, thymidine, was found to obviously prevent and/or retard the nanofiber formation of 1.