1979 Volume 99 Issue 10 Pages 976-981
Penetration of trifluoperazine (TFPeZ), a phenothiazine tranquilizer, into mixed monolayers of dipalmitoyl lecithin (DPL) and cholesterol (CH) was studied by measurement of surface pressure (F)-mean molecular area (A^^-34) curves. The amount of penetration (or adsorption) by TFPeZ was calculated by the modified Gibbs adsorption equation. Adsorption isotherms at a constant A^^-34 showed a type of Langmuir adsorption. Saturated amount of adsorption (Γ∞2) and Langmuir constant (k) were obtained by Langmuir plots. Correlation between those parameters and A^^-34 at various mixing ratios of DPL and CH were discussed. With decreasing A^^-34, Γ∞2 decreased in any DPL-CH mixed monolayer. The relation between Γ∞2 and composition of the monolayer at a constant A^^-34 corresponded well with the state of mixed monolayer, i.e. Γ∞2 is small in expanded monolayer rich in DPL (XDPL>XCH), and increases with decreasing XDPL down to XDPL=0.5. This increase corresponds to changes of the mixed monolayer state, from liquid expanded to solid condensed state. Below XDPL=0.5, in which the mixed monolayer is fully solid, Γ∞2 level is independent of the monolayer composition. Miscibility of penetrated TFPeZ with insoluble components, DPL and CH, was also discussed.
