Thermodynamic and Brewster Angle Microscopy Studies of Fatty Acid/Cholesterol Mixtures at the Air/Water Interface

Abstract

Mixtures of cholesterol with stearic (STA), oleic (OA), and linoleic (LA) acids spread as monolayers at the air/water interface were used as model systems to examine the hypocholesterolemic effect of fatty acids. Miscibility and interactions between the components of the cholesterol/fatty acid systems were studied basing on the analysis of surface pressure/area isotherms completed with Brewster angle microscopy images. In monolayers, STA and cholesterol were found to be immiscible. In contrast, OA and LA were found to form miscible, but nonideal mixed monolayers with cholesterol. They exhibit negative deviations from ideality in the surface pressure/area plots. This reflects close-packing arrangements between bulky cholesterol molecule and the hydrocarbon chains of unsaturated fatty acids. The analysis of the excess free energies of mixing shows that the maximum negative value of ΔG exc appears at about X chol = 0.5−0.7. Thus, the formation of the most stable 1:1 and 2:1 complexes between cholesterol and an unsaturated fatty acid molecule may account for the hypocholesterolemic effect of the acids in human organism by complexing free cholesterol, thereby hindering its deposition on artery walls.

MorphologicaObservation of Specific Condensation Effect of Cholesterol on Dipalmitoyl Phosphatidyl Choline (DPPC) Monolayer by Dropping Method

“…The brightness of image (l) was also similar to that of x C = 0.2 ((h)); the homogeneous mixed monolayer was formed on the water surface. These images ((i)-(l)) are similar to the monolayer formation process of such as stearic acid [18] and the following Chol ((m)-(p) in Figure 3), which forms the condensed monolayer on the water surface. Therefore, at x C = 0.3, a condensed monolayer was formed on the water surface from the initial stage of the monolayer formation.…”

“…On pure Chol monolayer, we obtained typical images that observed in the case of condensed monolayer [18]- [20]. At quite a low SP of 1 mN/m, the image showed lineand circle-type domain state ((m)), as well as x C = 0.3 ((I) in Figure 3).…”

Mixed layers of DPPC and a linear poly(ethylene glycol)-b-hyperbranched poly(glycerol) block copolymer having a cholesteryl end group

“…In our previous studies on polyether-based polymers with Ch moieties and systematically varied molecular architectures, it has been found that at this point the lPEG and hbPG blocks of ChP are located on the air-water interface (in addition to the Ch moiety) and contribute to the mmA value [54]. Thus, the Ch moiety is forced to be only in the G state and the LC domain formation typical for pure Ch in this region is prevented [60][61][62][63]. The Langmuir isotherms of the neat diblock copolymer in the relevant region are shown as gray curves in Fig.…”

CH/.PI. Interaction between Benzene and Hydrocarbons Having Six Carbon Atoms in Their Binary Liquid Mixtures

“…The excess molar volume [13][14][15] . shows the variation of V exc cyclo with x cyclo and also that of V exc hexane with x hexane at 30, 40 and 50 o C. Open symbols denote cyclohexane/benzene system and closed ones, hexane/benzene system.…”