EFFECTS OF FIBRINOGENS ON PHASE-TRANSITIONS IN LIPID MODEL MEMBRANE SYSTEMS

An abnormal fibrinogen that caused aggregation of red blood cells (RBC ) in a patient with gangrene was examined by real-time X-ray diffracti on to determine its effects on dipalmitoylphosphatidylcholine (DPPC) a nd 1-palmitoyl-,2-oleoylphosphatidylethanolamine (POPE) phase transiti ons. Similar studies were done with normal fibrinogen and results were compared. Both types of fibrinogen slightly increased the L(alpha) -- > H-II phase transition temperature and the H-II phase parameters for POPE, while neither fibrinogen significantly affected the order-disord ered acyl chain transitions in the lipid bilayer phase. However, fibri nogen differentially influenced the bilayer unit cell parameter of the gel and disordered bilayer and the gel state ripple phase. These resu lts can be interpreted as indicating that fibrinogen has little effect on the balance of gel and disordered acyl chains in the lipid bilayer , but may influence membrane functions dependent on non-bilayer phases .