The crystal structure of a $3_{10}$ helical decapeptide containing \alpha-aminoisobutyric acid

Alamethicin and several related \alpha-aminoisobutyric acid (Aib) containing natural and synthetic peptides form voltage-dependent channels across lipid bilayer membranes [1,2]. Their high Aib content constrains these peptides to adopt $3_{10}$ [2,3] or \alpha-helical conformations [1,4]. Membrane channels are then formed by helical peptide aggregation in the lipid phase [l-35], with a major role for the macrodipole moment of the peptide helices in mediating monomer association and channel characteristics [2,6].