Comparison of the membrane interaction and permeabilization by the designed peptide Ac-MB21-NH2 and truncated dermaseptin S3

Ac-MB21-NH2 (Ac-FASLLGKALKALAKQ-NH2) and dermaseptin S3(1-16)-NH2 (AL-WKNML KGIGKLAGK-NH2) are cationic amphipathic peptides with antimicrobial activit y against a broad spectrum of microorganisms including various fungi. The i nteraction of the peptides with liposomes was studied by exploiting the try ptophan fluorescence of F1W-Ac-MB21-NH2 and dermaseptin S3(1-16)NH2. Spectr al analysis and the use of quenchers indicate that the tryptophans of both peptides insert more deeply in anionic than in zwitterionic liposomes. Memb rane insertion con-elates with the formation of an alpha-helical peptide st ructure. Both peptides permeabilize liposomes composed of anionic, cylindri c phospholipids more efficiently than liposomes formed of zwitterionic, con ic (phospho)lipids.