Programming pH-triggered self-assembly transitions via isomerization of peptide sequence.

While the ordering of amino acids in proteins and peptide-based materials is known to affect their folding patterns and supramolecular architectures, tailoring self-assembly behavior in stimuli responsive peptides by isomerizing a peptide sequence has not been extensively explored. Here, we show that changing the position of a single hydrophobic amino acid in short amphiphilic peptides can dramatically alter their pH-triggered self-assembly transitions. Using palmitoyl-IAAAEEEE-NH2 and palmitoyl-IAAAEEEEK(DO3A:Gd)-NH2 as controls, moving the Isoleucine away from the palmitoyl tail preferentially induces nanofiber formation over spherical micelles.

Probing peptide amphiphile self-assembly in blood serum.

There has been recent interest in designing smart diagnostic or therapeutic self-assembling peptide or polymeric materials that can selectively undergo morphological transitions to accumulate at a disease site in response to specific stimuli. Developing approaches to probe these self-assembly transitions in environments that accurately amalgamate the diverse plethora of proteins, biomolecules, and salts of blood is essential for creating systems that function in vivo. Here, we have developed a fluorescence anisotropy approach to probe the pH-dependent self-assembly transition of peptide amphiphile (PA) molecules that transform from spherical micelles at pH 7.