Fig. 3.
The structure of induced HII phase changes with antimicrobial concentration. (A) Structure of phenylene ethynylene-based antimicrobial. (B Top) Formation of a transmembrane pore requires both negative and positive curvatures (black and red arrows, respectively). (Bottom) Schematic representation of how this PE-dependent structural tendency may be realized on a membrane, in which the antimicrobials recruit PE lipids to achieve the negative circumferential curvature necessary for pore formation. The white and green spheres represent headgroups of zero intrinsic curvature (e.g., DOPG, DOPC) and negative intrinsic curvature lipids (e.g., DOPE) respectively. The antimicrobials are represented by blue spherocylinders. (C) Synchrotron SAXS data show that the inverted hexagonal phase induced by antimicrobial in DOPG/DOPE = 20/80 membranes evolves structurally as antimicrobial to lipid molar ratio (A/L) varies from 1/122 to 1/9.5. (D) The integrated diffraction intensities increase in a sigmoidal manner and saturate at A/L ∼ 1/14.