Biophysical Imaging

Understanding the dynamics and organization of lipid membranes is a central topic in modern Biophysics. In fact, the molecular mobility of the lipid fraction is a very important factor in processes such as cellular signalling and immune cell activation. Imaging studies of these phenomena, however, require simultaneously high spatial and temporal resolution, which makes them particularly challenging. To fulfil these requirements, we adopted Interferometric Scattering Microscopy (iSCAT) to detect and interpret the motion of individual gold nanoparticle-tagged lipids on the plasma membrane of living cells at high sampling rates (2 kHz). We also developed a statistics-driven analysis scheme for Single Particle Tracking, to better evaluate the effect of localization error on fast tracking experiments and the diffusion mode of the target particle. Our results reveal that a large fraction of the lipids shows a compartmentalized, or hopping, diffusion mode. This study therefore not only provides a novel approach for the analysis of SPT data, but also highlights the viability and potential of iSCAT microscopy for lipid tracking on live cell membranes.