Abstrakt
Stimulated emission depletion combined with fluorescence correlation spectroscopy (STED-FCS) is one of the few techniques that can nowadays detect nanoscopic membrane heterogeneities in biological membranes by the analysis of so-called diffusion law plots. These plots relate diffusion coefficient to observation spot diameter, and despite their frequent use in membrane biophysics, the interpretation of these dependencies is often ambiguous without exploiting their full potential.
In this contribution, we show that a quantitative analysis of STED-FCS diffusion law plots provides unique information about the mobility of nanoscopic membrane heterogeneities as well as elucidates the diffusivity of individual lipids within these nanodomains. We demonstrate the applicability of this approach by performing STED-FCS experiments on nanoscopically heterogeneous membranes of giant lipid vesicles that contain ganglioside nanodomains of controllable size and membrane surface concentration.
The final interpretation of experimental diffusion law plots corresponding to dynamics of model membrane is accomplished by their comparison with in-silico simulations of lipid probe diffusion in heterogeneous bilayers. We demonstrate extended potential of diffusion law plots, and with the right analysis, we may learn considerably more specific details about the plasma and lipid vesicle membranes.