Lancing Liposomes: Unlocking the Mechanism of Short Amphiphilic Beta Sheet Forming Peptides

Abstract

Antimicrobial peptides (AMPs) are part of the innate immune system in humans and many other forms of life, exhibiting selective activity against bacterial cells, while leaving host cells unaffected. Of particular importance for this action is the difference in phospholipid composition of bacterial cells from cells of human tissue. Because of their antimicrobial and microbicidal characteristics, AMPs are of great interest for applications in human health, and non-natural AMPs have been devised to optimize the microbicidal characteristics of natural AMPs. It has been found that when dyad repeats are used in the pattern (XY)n, where X is a hydrophobic amino acid residue and Y is a cationic residue, a β-sheet secondary structure forms, and that these peptides are capable of killing bacteria, biofilms, and fungi. In this work, we design a synthetic 8 residue peptide using the (XY)¬¬n motif and conduct a series of biophysical tests on membrane mimicking lipid vesicles to elucidate a mechanism of antimicrobial action. A battery of biophysical tests is used to elucidate the significance of phospholipid membrane composition and the mechanism by which this peptide acts against bacterial cells. These studies include vesicle turbidity, kinetic vesicle leakage, and membrane fusion FRET assays. Taken together with previously performed biological assays, these results can aid in the elucidation of critical components of AMPs and in the design of stronger, more selective, AMPs.