Large, ethidium bromide-loaded liposomes electrically pulsed in the presenc
e of externally added DNA display the bright fluorescence of DNA-ethidium b
romide complexes. Sonication of these Liposomes increases the fluorescence
of trapped DNA-ethidium bromide complexes by no more than about 40%. These
results are thus in agreement with a mechanism involving electropores for D
NA uptake but do not support an alternative mechanism, invoking invaginatio
n and pinching-off of the lipid bilayer, through which internalized DNA is
shielded from the liposome contents. (C) 2000 Academic Press.