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 ves icles were treated by sodium dithionite, which undergoes an irreversible ch emical reaction with NBD-PC molecule making it non-fluorescent. After the a ddition of dithionite the fluorescence on single vesicles as well as on ves icle suspension showed a 50 % decrease of its initial value corresponding t o marker quenching in the outer leaflet. Hence, flourimetry as well as flou rescence microscopy prove that dithionite quenching is a suitable method to induce an asymmetrical labeling of the NBD-PC marked giant vesicles.