Hirosi Matuo

Mixed monolayers of cholesterol with fatty acids

Abstract The surface pressure versus mean area curves of the mixed monolayers of cholesterol with n-long chain fatty acids was obtained at various compositions and temperatures. It was observed that the area occupied by the expanded monolayer of fatty acid becomes somewhat smaller by addition of cholesterol. The surface pressure of the transition from expanded to condensed state varied with the composition and temperature, whereas the area occupied by the condensed monolayer composed of cholesterol and fatty acid satisfied the additivity rule. The two-dimensional phase diagram of the cholesterol-myristic acid system was constructed and the partial molar enthalpy of myristic acid was evaluated. It was concluded that cholesterol and fatty acid are miscible in the expanded state and immiscible in the condensed state and that the interaction between them is not specific but large enough to form the homogeneous expanded monolayer.

Azeotropic transformation in mixed monolayers of ethyl heptadecanoate and tetradecanoic acid

Abstract The surface pressure of mixed monolayers of ethyl heptadecanoate and tetradecanoic acid has been measured as a function of mean area at various compositions and temperatures. It has been observed that the phase transition takes place from the expanded to condensed monolayers over the whole range of compositions and the transition surface pressure has a maximum at a composition rich in tetradecanoic acid. With the aid of the thermodynamic method developed previously, the phase diagram has been constructed which is characterized by a positive azeotropy. Further, the molar entropy and energy changes associated with the phase transition have been calculated by applying the improved thermodynamic treatment. It has been clarified that the positive azeotropic transformation in the mixed monolayers is brought about by the mutual interaction between ethyl heptadecanoate and tetradecanoic acid molecules which is smaller than the interactions between the same kind of constituent molecules.

Effects of molecular structure on two-dimensional phase diagram and thermodynamic quantities of mixed monolayers☆

Abstract Many kinds of two-component mixed monolayer systems were investigated to clarify the effect of molecular structures on the monolayer state. Two-dimensional phase diagrams and thermodynamic quantities were evaluated by correct thermodynamic analysis. The diagrams were classified into the following six types: (1) cigar type; (2) modified cigar type; (3) positive azeotropic type; (4) negative azeotropic type; (5) eutectic type; (6) complicated type. Phase diagram analysis and thermodynamic quantities, such as entropy, enthalpy and energy changes, were in good agreement with each other.

Eutectic transformation in mixed monolayers of long normal chain fatty acids with 12-hydroxyoctadecanoic acid

Abstract Surface pressure of mixed monolayers composed of fatty acids and DL-12-hydroxyoctadecanoic acid (12HOA) was measured at various compositions and temperatures. Two-dimensional phase diagrams were constructed. Tridecanoic acid (C 13 )-12HOA, tetradecanoic acid (C 14 )-12HOA, pentadecanoic acid (C 15 )-12HOA, hexadecanoic acid (C 16 )-12HOA, and octadecanoic acid (C 18 )-12HOA systems showed eutectic transformations in mixed monolayers. Surface pressure of eutectic point decreased with increase in the carbon numbers of fatty acid. The mole fraction of 12HOA at the eutectic point increased with increase in the carbon numbers. However, eicosanoic acid (C 20 )-12HOA and docosanoic acid (C 22 )-12HOA systems were not of eutectic type; they were immiscible with each other in the mixed monolayer. Apparent molar entropy and energy changes of C 14 -12HOA and C 15 -12HOA systems were evaluated by previously mentioned thermodynamic treatment. The entropy and energy changes of C 14 and C 15 decreased slightly and steeply with increase in the mole fraction of 12HOA, χ 2 π , respectively. the values of 12HOA increased gradually with increase in χ 2 π .

Interrelationships between two-dimensional phase diagrams and mean molecular area-mole fraction curves in mixed monolayers

Abstract Both two-dimensional phase diagrams and mean molecular area (A)—mole fraction(x2π) curves have been investigated for various types of mixed monolayer systems. Two-dimensional phase diagram analysis and the behavior of A−x2π curves were found to be in good agreement with each other. From this result it was concluded that we should consider both phase diagrams and A−x2π curves of a mixed monolayer system in order to understand the behavior of the A−x2π curves.

Effects of molecular structure on positive and negative azeotropies in mixed monolayers of lipids

Abstract In order to clarify the effect of molecular structure on the nature of azeotropic transformations in mixed monolayers, many systems of the positive and negative azeotropic types are examined in this study. Two-dimensional phase diagrams and apparent molar energy changes which are associated with the phase transition from the liquid-expanded to the liquid-condensed state are evaluated using a previously developed thermodynamic treatment. There is a maximum in the phase diagram of the positive azeotropic type and the excess apparent molar energy change is positive over the entire compositional range. Steric hindrance of the hydrophilic groups seems to be the important factor in the behavior of the positive azeotropic type. For the negative azeotropic type there is a minimum in the phase diagram and the excess apparent molar energy change is negative over the entire compositional range. The two long acyl chains of dipalmitoyl lecithin leads to a strong interaction between the two components.

Mixed monolayers of dipalmitoylglycerophosphocholine, distearoylglycerophosphocholine and 1-palmitoylglycerol

Abstract Mixed monolayer systems of dipalmitoylglycerophosphocholine (DPPC)-distearoylglycerophosphocholine (DSPC), palmitoylglycerol-DPPC, and palmitoylglycerol-DSPC have been investigated by a previously described thermodynamic treatment. The surface pressures of these systems were measured at various compositions and temperatures. The two-dimensional phase diagrams and the apparent molar entropy and energy changes were evaluated. It was found that the phase diagrams of the DPPC-DSPC, palmitoylglycerol-DSPC and palmitoylglycerol-DPPC systems are all of different types. According to our phase diagram classification, DPPC-DSPC, palmitoylglycerol-DSPC, and palmitoylglycerol-DPPC systems exhibited a modified cigar type, a eutectic type, and a negative azeotropic type, respectively.

Mixed monolayers of fatty acids with distearoylglycerophosphocholine

Abstract Mixed monolayer states of long normal-chain fatty acids with distearoylglycerophosphocholine (DSPC) have been studied by a previously described thermodynamic treatment. The surface pressures of mixed monolayers of tetradecanoic, pentadecanoic and octadecanoic acids with DSPC were measured at various compositions and temperatures. The two-dimensional phase diagrams of both the tetradecanoic acid-DSPC and pentadecanoic acid-DSPC systems were determined. They both exhibited eutectic type phase diagrams. In the octadecanoic acid-DSPC system the two components were immiscible both in the liquid-expanded and liquid-condensed states. The apparent molar entropy and energy changes for the tetradecanoic acid-DSPC system were calculated. The values for tetradecanoic acid were negative, as is the usual case. However, the values of DSPC were positive, and their absolute values wer about 1 4 of that of tetradecanoic acid.