Stoichiometry of cholesterol-sphingomyelin condensed complexes in monolayers

Some binary mixtures of cholesterol and phospholipids in monolayers have th ermodynamic phase diagrams with two upper miscibility critical points. This feature has been interpreted in terms of condensed complexes' between the phospholipid and cholesterol. The present work gives evidence for the forma tion of complexes with a common simple integral stoichiometry in binary mix tures of cholesterol and a series of five sphingomyelins where the amide-li nked acyl chain length is varied. This indicates that these complexes have a distinct geometry even though they form a liquid phase. (C) 2001 Elsevier Science B.V. All rights reserved.