Lipid membrane-binding properties of tryptophan analogues of linear amphipathic beta-sheet cationic antimicrobial peptides using surface plasmon resonance

Using a surface plasmon resonance (SPR) system, we investigated the lipid membrane-binding properties of four analogues of the 18-residue linear amphipathic beta-sheet cationic antimicrobial peptide (KIGAKI)(3)-NH2, each of which contains a single isoleucine-to-tryptophan substitution. The results of the SPR study revealed significant differences in the binding characteristics of the peptides depending upon the position of tryptophan residues. These peptides showed higher binding affinity to membranes containing acidic phospholipids than zwitterionic phospholipids. The addition of dimethylsulfoxide to the running buffer was effective in maintaining the solubility of these peptide solutions and obtaining concentration-dependent sensorgrams for the kinetic analysis in this study. The kinetic binding data of SPR correlated closely with both the ability of the peptides to lyse liposomes with the same phospholipid composition and bactericidal activity. The results demonstrate that SPR may be a valuable tool to predict the membrane lytic properties of antimicrobial peptides.