Product Introduction Phosphatidylserine (PtdSer) is an anionic phospholipid abundantly present in the eukaryotic cell. 10% of the total cellular lipid consists of phosphatidylserine. O‐phospho‐L‐serine is a heat‐stable substrate. Application 16:0 PS has been used in the assay to measure interactions between purified dynamin-related protein 1 (Drp1) and synthetic liposomes. 16:0 PS may be used in liposome flotation assay to measure its interactions between purified dynamin related protein 1 (Drp1) and as a component in the lipid mixtures to prepare lipid monolayers. It has also been used to prepare liposomes by the lipid film hydration method.