Dipalmitoylphosphatidyl choline

The environment of a cell membrane is often modeled by a monolayer of phospholipid on the air-water interface. Our attempts to detect enantiomeric recognition in such films has largely involved dipalmitoylphosphatidyl choline (DPPC), which has a chiral headgroup situated at the junction of two 16-carbon unit chains. 

Fig. 13 Force/area curves of dipalmitoylphosphatidyl choline monolayers spread on pure water at 25°C (solid line) and 45°C (dashed line). The compression rate is 7.2 A2/molecule per minute. The shape of the isotherms is identical for homochiral and heterochiral films.

Fig. 15 Force/area curves for monolayers of dipalmitoylphosphatidyl choline (solid line), dimyristoylphosphatidyl choline (dashed line), and dilauroylphosphatidyl choline (dotted line) at 25°C.

Curve B pyranine trapped in the thin water layer (30 A thickness) of multi-lamellar vesicles made of dipalmitoylphosphatidyl choline (pH 5.5) ... 

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.)... 

The structural dependence of phospholipid solutions on water content is called lysotropic polymorphism. At a water content of up to 30% dipalmitoylphosphatidyl-choline (DPPC) forms lamellar phases consisting of superimposed bilayers. Increasing the water content results in heterogeneous dispersions formed by multilamellar structures, the so-called liposomes (see also Section 1.3.1). 

Lekner, J. (1987). Theory of Reflection, Martinus Nijhoff, Dordrecht, The Netherlands. Lewis, D. and Hadgraft, J. (1990). Mixed monolayers of dipalmitoylphosphatidyl-choline with Azone or oleic acid at the air-water interface. Int. J. Pharm. 65 211-218. 

Gardam M, SUvius Jr. Intermixing of dipalmitoylphosphatidyl-choline with phosphohpids and sphingoUpids bearing highly asymmetric hydrocarbon chains. Biochim. Biophys. Acta 1989 980 319-325. 

When synthetic lipids are used, detergent removal has to be performed above the corresponding transition temperature T of the lipid. Hence, when for example dipalmitoylphosphatidyl choline (DPPC) is used as main liposome forming lipid, a temperature above its T of 4DC has to be chosen. Additional membrane forming components (cholesterol, lipophilic drugs, etc.) depress the T by several degrees. 

The respiratory distress syndrome (RDS) of a premature infant such as Colleen Lakker is, in part, related to a deficiency in the synthesis of a substance known as lung surfactant. The major constituents of surfactant are dipalmitoylphosphatidyl-choline, phosphatidylglycerol, apoproteins (surfactant proteins Sp-A,B,C), and cholesterol. 

Bhattacharya S, Moss RA, Ringsdorf H, Simon J. A pol3uneric flippase for surface-differentiated dipalmitoylphosphatidyl-choline liposomes. J Am Chem Soc 1993 115 3812-3813. 

When the gaseous monolayer is compressed, a transition into the so-called liquid-expanded phase usually takes place. This phase has been the subject of many controversies. Most of this discussion, however, took place before the structure of the lamellar liquid crystalline phase was known. It should be mentioned in this connection that Phillips et al. (1969) used such correlations in their interpretation of the monolayer structure of dipalmitoylphosphatidyl-choline which will be further discussed in Section 8.10. 

Figure 9.17 Raman spectra of 1,2-dipalmitoylphosphatidyl-choline in the a) polycrystalline, b) multilayer and (c) vesicle forms in the 1020-1170 cm" region utilizing 515.5 nm excitation (Spiker and Levin, 1976a).

The incorporation of insulin into liposomes was done to deliver it specifically to the liver (a natural target organ for liposomes), prolong insulin action in the body, and enhance the oral absorption of insulin (early studies were reviewed in Ref. 322) Later, the liposomal insulin was used for intratracheal admninistration. It was shown that insulin incorporation into liposomes made of dipalmitoylphosphatidyl choline and cholesterol (7 2) resulted in an improved pulmonary uptake of insulin in rats and enhanced the h)q)oglycemic effect. 

Alvarez, J. G., Slomovic, B., and Ludmir, J. (1995). Analysis of dipalmitoylphosphatidyl-choline in amniotic fluid by enzymic hydrolysis and high-performance thin-layer chromatography reflectance spectrodensitometry. J. Chromatogr., B Biomed. Appl. 665 79-87. 

Differential scanning calorimetry provides numerical thermodynamic data and is frequently the main technique used to determine phase diagrams [40,46-57]. Some surfactant systems studied by DSC analysis in the literature are soap-water [41-43], dipalmitoylphosphatidyl choline-water [17,44], sodium dodecylsul-fate-water [13], CwPO-water [1,2,6], perfluorosurfactants-water [45], and dioc-tadecyldimethylammonium bromide-water [46]. 

Feigner, P. L., Freire, E., Barenholz, Y., and Thompson, T. E., 1981, Asymmetric incorporation of trisialoganglioside into dipalmitoylphosphatidyl choline vesicles. Biochemistry 20 2168-2172. 

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