Design and Synthesis of a Diamino Diacid-based Short Cyclic Peptide with Tunable Self-Assembly

Cyclic peptide nanostructures are thought to be potential candidates for biomedical applications because of their biocompatibility.The diamino diacid residues are formed from two -amino acid units, which are coupled with a linker.They have been used as external templates for synthesizing short cyclic peptides (CP). We have used a diamino diacid for the preparation of a cyclic heptapetide with an aliphatic chain connecting the two terminal -amino acid units. The properties of this cyclic peptide were compared with that of the corresponding linear peptide (LP).It was found that the CP showed concentration dependent self-assembly resulting in the formation of different nanostructures at different concentrations. These self-assembled nanostructures were characterized using FESEM, AFM, DLS, and FTIR.The study showed that the self-assembling behaviors of the cyclic and linear peptides are significantly different.Both the CP and the LP have very low critical aggregation concentrations (CAC), which were measured using fluorescence and DLS.The conformations of the CP and LP were analyzed at different concentrations using CD spectroscopy and marked differences were observed in their native conformations at different concentrations and solvents.