Probing The Interaction Forces Between Hydrophobic Peptides And Supported Lipid Bilayers Using Afm

Despite the vast body of literature that has accumulated on tilted peptides in
the past decade, direct information on the forces that drive their interaction
with lipid membranes is lacking. Here, we attempted to use atomic force
microscopy (AFM) to explore the interaction forces between the Simian
immunodeficiency virus peptide and phase-separated supported bilayers composed of
various lipids, i.e. dipalmitoylphosphatidylcholine, dioleoylphosphatidylcholine,
dioleoylphosphatidic acid and dipalmitoylphosphatidylethanolamine.
Histidine-tagged peptides were attached onto AFM tips terminated with
nitrilotriacetate and tri(ethylene glycol) groups, an approach expected to ensure
optimal exposure of the C-terminal hydrophobic domain. Force-distance curves
recorded between peptide-tips and the different bilayer domains always showed a
long-range repulsion upon approach and a lack of adhesion upon retraction, in
marked contrast with the hydrophobic nature of the peptide. To explain this
unexpected behaviour, we suggest a mechanism in which lipids are pulled out from
the bilayer due to strong interactions with the peptide-tip, in agreement with
the very low force needed to extract lipids from supported bilayers.