FIG. 6. .

Influence of virus protein VP4 on the phase behavior of a model lipid mixture. The lipid mixture used in these experiments contained phosphatidylethanolamine-phosphatidylserine-sphingomyelin-cholesterol (50/17/15/18 [mol/mol]). Lipids were fully hydrated at pH 8 in the presence of calcium (1 cation/100 lipids). (A) The lipid mixture adopts an inverted-hexagon arrangement characterized by a periodicity of 6.4 nm between 10 and 45°C. A trace of Pn3m-type cubic phase is detected in the small-angle area at the highest temperatures recorded. (B) In the presence of VP4 the lamellar phase (repeat distance, 6.45 nm) is preferred. Above 37°C the lamellar arrangement coexists with an inverted-hexagon phase (repeat distance, 6.31 nm).