The design, synthesis, and characterization of "reverse" peptide amphiphiles (PAS) with free N-termini is described. Use of an unnatural amino acid modified with a fatty acid tail allows for the synthesis of this new class of PA molecules. The mixing of these molecules with complementary ones containing a free C-terminus results in coassembled structures, as demonstrated by circular dichroism and NOE/NMR spectroscopy. These assemblies show unusual thermal stability when compared to assemblies composed of only one type of PA molecule. This class of reverse PAS has made it possible to create biologically significant assemblies with free N-terminal peptide sequences, which were previously inaccessible, including those derived from phage display methodologies.