  The effect of solute, sodium deoxycholate bile salt (DOCNa), on the
cooperativity of ordered-fluid, fosfolipid phase transition has been
investigated by determining of the transition widths in multibilayer
dispersions of the dipalmitoylphosphatidylcholine (DPPC)-DOCNa mixtures. The
DT1/2 values were determined by differential scanning calorimetry. The van't
Hoff values of the main transition enthalpies were calculated using an
approximative expression, deduced from Zimm and Bragg theory
[Sturtevant,J.M.(1982), Proc.Natl.Acad.Sci.USA,79:3963-3967]. The bile salt
decreases the cooperativity (size of cooperative unit) of DPPC bilayers.
