High-resolution structure of coexisting nanoscopic and microscopic lipid domains

Abstract

We advanced a previously reported model for the \textit{in situ} scattering data analysis of coexisting lipid domains in free-floating multilamellar vesicles. Based on the scattering density profile of the individual domains we considered in particular modifications due to positionally anticorrelated domains or the presence of cholesterol. The latter aspect can be easily extended to any other lipophilic molecule. This allowed us to retrieve elastic and structural details (bending fluctuations, domain thickness, area per lipid) of coexisting liquid-ordered/liquid-disordered domains, including the partitioning of cholesterol from small-angle x-ray scattering experiments. Moreover, the model also successfully fitted data of multilamellar vesicles exhibiting nanoscopic domains, which displayed unlike coexisting micron-sized domains no clear signal for two lamellar lattices. Our results indicate a previously not observed translation of cholesterol toward the bilayer center of nanoscopic liquid-ordered domains.