Solid supported multicomponent lipid membranes studied by x-ray spectromicroscopy

This article addresses the lateral organization of two-component lipid membranes deposited on a solid support with the addition of colloidal particles. The authors have applied synchrotron-based scanning transmission soft x-ray spectromicroscopy to image thin lipid layer patches with bound microspheres coated by a charged monolayer. The ability and current limits of scanning transmission x-ray spectromicroscopy to examine samples under physiologically relevant conditions in the presence of excess water have been tested. In particular, the authors have investigated a range of model lipids and have shown that these can be reproducibly identified from the near-edge x-ray absorption fine structure spectra at the carbon K absorption edge. Reference spectra were obtained based on a compact laser-driven plasma source, while the spectromicroscopy data were collected using synchrotron radiation at a lateral resolution of about 60 nm. The authors show that thin lipid layer sensitivity can indeed be reached under physiological conditions and that membrane colloid interaction as well as eventual lateral segregation of lipid components may be probed in the future by this technique.