The invention relates to an isolated peptide tetramer comprising the formula [(RGRKWRR) 2 K] 2 KK and its derivatives thereof. The derivatives may comprise at least one amino acid substitution, at least one amino acid deletion, a rearrangement of the peptide monomer and/or at least one non-proteogenic amino acid modification in at least one peptide monomer. The isolated peptide tetramer and derivatives thereof have antimicrobial (antibacterial, antifungal and/or anti-protozoan) properties.
