Exploring the structural relationship between encapsulated antimicrobial peptides and the bilayer membrane mimetic lipidic cubic phase: studies with gramicidin A′

Abstract

Lipid based bicontinuous cubic mesophases provide a low-cost, robust membrane mimetic nanomaterial which allows for the incorporation of membrane peptides and proteins. However, the relationship between the mesostructure of the host lipidic bicontinuous mesophase, the chemical structure of its constituents, and the secondary structure of encapsulated biomolecules is complex, and at present largely unclear. Here we have examined the effects of adding gramicidin A′, an anti-microbial peptide, to lipidic bicontinuous cubic phases composed of a number of different lipids. We demonstrate, using a combination of synchrotron small angle X-ray scattering and circular dichroism, that fundamental physicochemical parameters of the lipid mesophase impact both the structural response to peptide addition, and the conformation of the encapsulated peptide. We have rationalised the results with reference to hydrophobic mismatch, the putative lateral pressure profile and the intrinsic surface curvature of each lipid system. Results should be of use for several applications of hybrid peptide-lipid materials including peptide based drug delivery and the design of in meso crystallization trials.