Stereochemical Effects on the Self-Assembly of Pyrenylalanine-Phenylalanine Dipeptide

The design and control of self-assembling biomaterials have significantly attracted attention over the last decades because of their broad ranges of applications. Here, we introduce the self-assembled fibers of the pyrene connected dipeptides, L-pyrenylalanine-L-phenylalanine (L-Pyr-L-Phe) and D-pyrenylalanine-L-phenylalanine (D-Pyr-L-Phe), and their structural analysis using experimental and computational techniques. While L-Pyr-L-Phe self-assembled into solid fibers, D-Pyr-L-Phe self-assembled into hydrogels with different morphologies. Fluorescence spectroscopy revealed monomer and red-shifted excimer emissions of the self-assembled L-Pyr-L-Phe and D-Pyr-L-Phe dipeptide nanostructures, respectively. This result was related to different C-13 and N-15 solid-state nuclear magnetic resonance (NMR) data on the backbone and side-chains of the self-assembled dipeptides. Molecular dynamics simulations demonstrated detailed information about the chirality effects of the dipeptides on their self-assembled structures.