The ability of lysophosphatidylcholine to inhibit membrane fusion at s
ubsolubilizing concentrations (between 1 and 9 mol % with respect to t
he membrane lipids) was examined. Fusion between N-methyldioleoylphosp
hatidylethanolamine (DOPE) large unilamellar vesicles (LUV) and fusion
between Sendai virus and N-methyl-DOPE LUV were measured. A contents
mixing fusion assay was used for LUV fusion (ANTS/DPX), and a lipid mi
xing assay (octadecylrhodamine B) was used for the virus fusion experi
ments. Lysophosphatidylcholine was effective at inhibiting both LUV fu
sion and Sendai virus/LUV fusion. Lysophosphatidylcholine also inhibit
ed leakage from N-methyl-DOPE LUV. P-31 nuclear magnetic resonance dat
a were obtained of N-methyl-DOPE in the presence of lysophosphatidylch
oline. Lysophosphatidylcholine stabilized the lamellar phase and reduc
ed the incidence of nonlamellar structures at all temperatures. The de
stabilization of nonlamellar structures with a negative radius of curv
ature may be a mechanism for inhibition of fusion by lysophosphatidylc
holine in these systems.