Gaegurin 4 (GGN4), a 37-residue antimicrobial peptide, consists of two amphipathic ahelices (residues 2–10and 16–32) connected by a flexible loop region (residues 11– 15). As part of an effort to develop new peptide antibiotics with low molecular mass, the activities of C-terminally truncated GGN4 analogues were tested. D 24)37 GGN4, a peptide analogue with 14 residues truncated from the C-terminus of GGN4, showed a complete loss of anti-microbial activity.