THE CONFORMATION OF LINEAR GRAMICIDIN IS SEQUENCE-DEPENDENT

A comparative monolayer and infrared study of analogues of gramicidin A containing either tyrosines or naphthylalanines instead of tryptopha ns indicates that the nature of the aromatic residues influences the f avoured conformation of the peptides. Polar residues favour the single stranded IIDL helix while non polar residues favour the double strand ed helix. For partly tryptophan to naphthylalanine substituted analogu es the positions of the substitutions orientate the favored conformati on. The nature of these substitutions may also modify the peptide-lipi d interactions.