Super-resolution microscopy of lipid bilayer phases.

Sub-diffraction optical imaging with nanometer resolution of lipid phase-separated regions is reported. Merocyanine 540, a probe whose fluorescence is sensitive to the lipid phase, is combined with super-resolution imaging to distinguish the liquid- and gel-phase nanoscale domains of lipid bilayers supported on glass. The monomer-dimer equilibrium of MC540 in membranes is deemed responsible for the population difference of single-molecule fluorescence bursts in the different phase regions. The extension of this method to other binary or ternary lipid models or natural systems provides a promising new super-resolution strategy.