Synthesis and Antimicrobial Evaluation of Amphipathic Peptide Models

Two groups of amphipathic peptides, based on the Schiffer/Edmundson helical-wheel model, were designed, synthesized and their antimicrobial and hemolytic activities were studied. The first group includes the peptides X-RWLRLLWRFLRL-NH2, where X=H, Ac, Ahx (aminohexanoic) and Myr (Myristoyl). Specific substitutions were introduced in the hydrophobic /hydrophilic face or the N-terminal group in order to investigate how these modifications affect their antimicrobial activity. The second group comprises three analogs of aurein 1.2 H-GLFDIIKKIAESF-NH2, a natural antimicrobial amphipathic peptide, obtained by replacing Gly with Ala, Val and Leu successively. The influence of these modifications on the reactivity of aurein was also studied. The helical conformation of the synthetic peptides was evaluated by circular dichroism. Comments regarding the nature, the total charge and the availability of the N-terminal groups are discussed in relation to the antimicrobial reactivity of the reported peptides.