Short-chain analogues of the lipopeptaibol antibiotic trichogin GA IV: conformational analysis and membrane-modifying properties

To examine the role of the peptide main-chain length on the conformation and membrane activity of the lipopeptaibol antibiotic trichogin GA IV we have synthesized by solution methods the Leu(11)-OMe analogue and all its short, N-octanoylated C-terminal sequences. By FTIR absorption, H-1 NMR and CD we have shown that largely folded, but not helical, forms characterize the short peptides, while the longest peptides predominantly adopt regular helical structures. Membrane activity is found in main-chain lengths as short as the tetrapeptide and progressively increases up to the undecapeptide.