Association of blood clotting factors I and VII with phospholipid monolayers at the air-water interface

Phospholipid monolayers adsorbed at the air-water interface are useful mode l membranes and have been employed to study the interactions between phosph olipids and blood clotting factors I and VII. Factor I is a non-membrane-bi nding protein and was found to penetrate both distearoylphosphatidylcholine (DSPC) and dipalmitoylphosphatidylcholine (DPPC) monolayers at low lipid p ressures. At high lipid pressures, the protein was crowded out of the inter face. Factor I penetration of phospholipid monolayers was independent of hy drocarbon chain length, while penetration was maximized with electrolytes i n the subphase, Factor VII is a membrane binding protein and was found to p enetrate a DPPC monolayer only when electrolytes were added to the subphase , Factor VII penetrated DSPC monolayers regardless of electrolyte addition in the subphase, and its interactions with DSPC films are attributed to pro tein-lipid hydrophobic interactions, (C) 1999 Academic Press.