Hydrophobicity, hydrophobic moment and angle subtended by charged residues modulate antibacterial and haemolytic activity of amphipathic helical peptides.

The hydrophobicity (H), hydrophobic moment (mu) and the angle subtended by the positively charged helix face (phi) of a set of model and magainin 2 amide peptides with conserved charge and helix propensity have been shown to be effective modulators of antibacterial and haemolytic activity. Except peptides of low hydrophobicity which are inactive, changing the parameters has little influence on the activity against Gram-negative bacteria, thus revealing the dominance of electrostatic interactions for the effect. However, the increase of H, mu and phi substantially enhances haemolytic and Gram-positive antibacterial activity and is related to a reduction of peptide specificity for Gram-negative bacteria.