Structural studies of amphiphilic oligopeptides composed of alternating alanine and ionizable amino-acid residues using CD and 13C CPMAS NMR spectroscopy

We report a novel self-assembling system of amphiphilic oligopeptides composed of alternating hydrophobic and ionizable amino-acid residues. Three types of peptides, AD12, AE12 and AK12, were prepared as building blocks for this model system. These peptides formed helical conformations in low-concentration solutions, but these peptides adopted b-sheet structures and precipitated in highly concentrated solutions at a pH that neutralizes the charges on the ionizable side chains. In addition, the mixing of the peptides with positive and negative charges on the side chains of the ionizable amino-acid residues was found to trigger the formation of the b-sheet structure. This system could be used to create new materials based on oligopeptides. Polymer Journal (2012) 44, 882–887; doi:10.1038/pj.2012.115; published online 20 June 2012