Gel‐ and Solid‐State‐Structure of Dialanine and Diphenylalanine Amphiphiles: Importance of C⋅⋅⋅H Interactions in Gelation

To investigate the role of the capping group in the solution and solid‐state self‐assembly of short peptide amphiphiles, dialanine and diphenylalanine have been linked via the N‐terminus to a benzene (phenyl) and 3‐naphthyl capping groups using three different methylene linkers; (CH2)n, n=0–4 for the benezene and 0, 1 and 2 for the naphthalene capping group. Atomic force microscopy (AFM), oscillatory rheology, circular dichroism (CD), and IR analysis have been employed to understand the properties of these peptide‐based hydrogels. Several X‐ray structures of these short peptide gelators give useful conformational information regarding packing. A comparison of these solid state structures with their gel state properties yielded greater insights into the process of self‐assembly in short peptide gelators, particularly in terms of the important role of C⋅⋅⋅H interactions appear to play in determining if a short aromatic peptide does form a gel or not. Peptide gels and crystals: A series of 16 aromatic peptide amphiphiles have been prepared and the ability to form self‐assembled hydrogels investigated. X‐ray structures were obtained for 8 out of 16 of these short peptide gelators. A comparison of these solid state structures with their gel state properties yielded greater insights into the process of self‐assembly these peptides, particularly in terms of the important role of C⋅⋅⋅H interactions appear to play in gelation.