Design of membrane-inserting peptides: spectroscopic characterization with and without lipid bilayers

Two synthetic peptides, Ala and Leu, were characterized by Fourier transform infrared spectroscopy, polarized infrared spectroscopy and circular dichroism spectroscopy, with curve-fitting analysis. The Ala peptide had a beta structure in solution whereas the Leu peptide had a helical structure. Only Leu was shown to bind strongly to the lipid bilayer vesicles and it did not precipitate in buffered solutions. The slow kinetics displayed by Leu suggest complex multiple structures.