Antimicrobial peptides (AMPs) are produced by a variety of organisms as an essential component of their immune systems. Although AMPs are thought to kill bacteria through membrane disruption, the relationship between AMP structure and activity is not well understood. Quartz crystal microbalance with dissipation (QCM-D) was used to monitor the action of four AMPs: alamethicin, chrysophsin-3, indolicidin, and SMAP-29 (Sheep Myeloid Antimicrobial Peptide) on a supported phosphatidylcholine (PC) lipid bilayer. The four peptides representing diverse charge, hydrophobicity, and structural characteristics, interacted with the PC membrane distinctly differently as indicated by the QCM-D signatures of frequency and dissipation changes.  Alamethicin, a practically neutral, a-helical peptide, inserted into the lipid bilayer beginning at AMP concentrations as low as 0.05 �M. Chrysophsin-3, an a-helical peptide with 4 net charges, adsorbed to the membrane surface and formed pores below 5 �M and lost lipid mass at 10 �M, possibly due to the formation of peptide-lipid aggregates. Indolicidin, a short, tryptophan-rich peptide with random coil conformation, adsorbed to and inserted into the membrane, but no major membrane disruption was observed up to 10 �M.  SMAP-29, a strongly cationic peptide, adsorbed to the membrane and inserted to form pores, but did not cause significant loss of lipids from the bilayer. While the QCM-D signatures are very distinct between the four peptides, their unambiguous quantitative molecular interpretation requires additional, complementary methods of investigation.

Using QCM-D to compare the actions of antimicrobial peptides alamethicin, chrysophsin-3, indolicidin, and SMAP-29 on a supported lipid membrane

245th National Meeting (2013)

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