Asymmetrical labeling of giant phospholipid vesicles

The method for labeling of inner membrane leaflet in unilamellar giant POPC vesicles was developed and characterised. Symmetrically NBD-PC labeled vesicles were treated by sodium dithionite, which undergoes an irreversible chemical reaction with NBD-PC molecule making it non-fluorescent. After the addition of dithionite the fluorescence on single vesicles as well as on vesicle suspension showed a 50 % decrease of its initial value corresponding to marker quenching in the outer leaflet. Hence, flourimetry as well as flourescence microscopy prove that dithionite quenching is a suitable method to induce an asymmetrical labeling of the NBD-PC marked giant vesicles.