Glycolipid–cholesterol monolayers: Towards a better understanding of the interaction between the membrane components

In this work, the interaction between a synthetic analog of archaeal lipids and cholesterol was studied using Langmuir technique. The lipid, β-Mal3O(C16 + 4)2, contained phytanyl chains attached via two ether bonds to the sn-2 carbon of the glycerol backbone. The preliminary studies showed that monolayers formed with the pure lipid have a liquid-like character; here, a hypothesis that admixing cholesterol to β-Mal3O(C16 + 4)2 could confer a higher rigidity on the films was tested. To check this proposal, two-dimensional miscibility of cholesterol and β-Mal3O(C16 + 4)2 in monomolecular films was studied using surface pressure and surface potential measurements, as well as Brewster angle microscopy and polarization-modulation infrared reflection absorption spectroscopy. The stability of the monomolecular films was evaluated based on thermodynamics of mixing of cholesterol and β-Mal3O(C16 + 4)2. Atomic level information concerning the orientation of molecules and the degree of hydration of polar headgroups was obtained from molecular dynamics simulations.