Detecting membrane lipid microdomains by two-photon fluorescence microscopy

This article discusses our ability to obtain, using two-photon excitation, microscopy images of the generalized polarization (GP) of the lipid probe 2-dimethylamino-6-lauroylnaphthalene (LAURDAN) in phospholipid vesicles and in natural membranes. The images show different distribution of the GP value depending on membrane composition. The use of linearly polarized excitation allowed the attribution of the GP heterogeneity to coexisting membrane domains of different dynamic properties. Based on the photoselection operated by the excitation polarization, we propose a model to explain our results and to estimate the domains' dimension.