TABLE 1.

Influence of length and salinity on antibacterial activitya

PeptideLength (no. of residues)MBC (μM) against:
P. aeruginosa PA1244 in:S. aureus in:
PBPBSPBPBS
LL37371.21.22.5>10
LBU112>10>10>10>10
LBU2240.60.61.2>10
LBU3361.20.60.61.2
LBU4480.30.30.30.3
WLBU1120.6>10>10>10
WLBU2240.30.30.30.3
WLBU3362.50.62.50.3
WLBU4482.50.62.50.6
LBU1.3151.2>10>10>10
LBU1.6181.2>102.5>10
LBU1.9210.62.51.2>10
  • a The MBCs (peptide concentrations promoting 99.9% killing) of the LBU and WLBU series in PB and in PB plus 150 mM NaCl (PBS) were derived from the dose-dependent survival curves as previously described (26). The human cathelicidin LL37 was used as a comparative host-derived peptide in these experiments. There was no significant change in antibacterial activity in the peptides of 24 to 48 residues in length, but the peptide LBU2 was salt sensitive against S. aureus. The relationship between length and activity was further characterized by using peptides of 12, 15, 18, 21, and 24 residues. The results of these studies reveal that a minimum length of 15 residues is required for significant antibacterial activity. Average MBCs were obtained from three to five experimental trials.