Studying interactions with lipid bilayer surfaces using Dual Polarisation Interferometry

Speaker

Gerry Ronan, Farfield Group Ltd., United Kingdom.

Abstract

Increasingly, a diverse range of structural biophysical techniques, such as x-ray and neutron scattering techniques, are being used to study the nature of lipid bilayers and their interactions. However, these techniques provide information regarding the steady-state situation of the lipid bilayer, rather than dynamic information about the bilayer behaviour during interactions.

Dual Polarisation Interferometry (DPI) provides a dynamic biophysical measurement to follow the formation of a lipid bilayer, characterising the quality of the layer by measuring both the surface adsorbed mass and its birefringence1. This provides a means of quantifying the lipid bilayer by its packing and order and allows the study of subsequent interactions of peptides and proteins by tracking these dynamically. In this way, DPI reveals a whole new area of lipid-mediated biomolecular interactions, how the structure changes due to environmental effects (temperature, ionic strength, etc) or by the interaction of peptides (antimicrobials, amyloids, prions, etc) and other membrane proteins. Ultimately, the technique shows great promise as an assay platform to study receptor inhibition by drug candidates.

During peptide association with the bilayer (mass increase), birefringence decreasing reveals the absorption of the peptide into lipid layeras distinct from adsorption to the lipid surface (see above). Micellisation, e.g. due to antimicrobial action, results in a decrease in both the mass and birefringence. As the technique is dynamic (10Hz), kinetics of interaction during each phase can be measured and as the method is quantitative, stoichiometry of reaction can be calculated.