For the enzymatic reactions of the coagulation cascade to occur at physiologically relevant rates, the protein components must be localized to an appropriate membrane surface comprised of negatively-charged phospholipids (1). Activated platelets (2,3) and to a lesser extent mononuclear cells (4) provide this membrane surface in vivo, and synthetic phospholipid vesicles comprised of 75% phosphatidylcholine (PC) and 25% phosphatidylserine (PS) (PCPS) can support these reactions in vitro in various assays (5-8). PCPS vesicles can also support membrane-dependent anticoagulant reactions in purified (9) and plasma-based hemostasis assays (10).
Unilamellar PCPS vesicles consisting of 75% PC and 25% PS are prepared from L-α-phosphatidylcholine (chicken egg) and L-α-phosphatidylserine (porcine brain) (11) and quantified by phosphate assay (12). They are provided as a lyophilizate and should be stored at 4°C prior to and following reconstitution.