Dipalmitoylphosphatidylcholine-cholesterol mixtures

Muramatsu, K., et al. 1994. Effect of soybean-derived sterol and its glucoside mixtures on the stability of dipalmitoyl-phosphatidylcholine and dipalmitoylphosphatidylcholine/cholesterol liposomes. Int J Pharm 107 1. 

Fig. 11. Evidence that a membrane-associated immunochemical reaction (complement fixation) depends on the mobility of the target hapten (IX) in the plane of a model membrane. The extent of the immunochemical reaction, complement fixation, is measured by A Absorbance at 413 nm. Temperature is always 32°C, which is above the chainmelting temperature (23°C) of dimyristoylphosphatidylcholine used for the data given in A and below the chain-melting transition temperature (42°C) of dipalmitoylphosphatidyl-choline used for the data in B. Thus A refers to a fluid membrane and B refers to a solid membrane. The numbers by each curve are equal to c, the mole % of spin-label hapten IX in the plane of the lipid membrane. It will be seen that complement fixation, as measured by A Absorbance at 413 nm is far more effective in the fluid membrane than in the solid membrane at low hapten concentrations (i.e., c 0.3 mo e%). In C the lipid membrane host is a 50 50 mole ratio mixture of cholesterol and dipalmitoylphosphatidylcholine. The immunochemical data suggest that this membrane is in a state of intermediate fluidity. Specific affinity-purified IgG molecules were used in these experiments. (For further details, see Ref. 5.)... 

Liposomes were formed from 1,2-dipalmitoylphosphatidylcholine (DPPC) and cholesterol (Choi) and the effect of liposomal entrapment on pulmonary absorption of insulin was related to oligomerization of insulin (Liu et al. 1993). Instillation of both dimeric and hexameric insulin produced equivalent duration of hypoglycemic response. However, the initial response from the hexameric form was slightly slower than that from dimeric insulin, probably due to lower permeability across alveolar epithelium of the hexameric form caused by larger molecular size. The intratracheal administration of liposomal insulin enhanced pulmonary absorption and resulted in an absolute bioavailability of 30.3%. Nevertheless, a similar extent of absorption and hypoglycemic effects was obtained from a physical mixture of insulin and blank liposomes and from liposomal insulin. This suggests a specific interaction of the phospholipid with the surfactant layer or even with the alveolar membrane. 

Vist, M. and Davis, J. Phase equilibria of cholesterol/dipalmitoylphosphatidylcholine mixtures 2H nuclear magnetic resonance and differential scanning calorimetry. Biochemistry, 29, 451,1990. 

S. Mabrey, P. L. Mateo, and J. M. Sturtevant, High Sensitivity Scanning Calorimetric Study of Mixtures of Cholesterol with Dimyristoyl- and Dipalmitoylphosphatidylcholine, Biochemistry 17, 2464-2468 (1978). 

The quantitative determination of phospholipid acyl chain conformational disorder in hydrated systems of dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamlne (DPPE), mixtures containing DPPC and cholesterol, and mixtures of DPPC and Gramicidin D has been made using FT-IR. The... 

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