1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (PAPC lipid) is a glycerophospholipid, with substitution of palmitic acid and docosahexaenic acid at sn-1 and sn-2 positions of the glycerol backbone. It has been used in liposome extrusion and liposome flotation assay.