Dipalmitoylphosphatidylcholine, DPPC

The rate of transport across bilayer membranes reconstituted from dipalmitoylphosphatidylcholine (DPPC) andnigericin is approximately the same as that observed across membranes reconstituted from DPPC and cecropin a at 35 C. Would you expect the transport rates across these two membranes also to be similar at 50 C Explain. 

Jizomoto and Hirano [3.41 ] tried to increase the amount of drug inclusions in liposomes by inserting Ca2+ ions in dipalmitoylphosphatidylcholine (DPPC) liposomes. The included volume (mL) per g of liposomes is called Vcap, and this can be increased as a function of the Ca2+ concentration up to ten fold of the minimum Vcap The increase in Vcap is attributed to the electrostatic repulsion between the Ca ions, which reduces the number of lamella and increases the diameter of the liposomes to a certain extent, but increases substantially. A calculated simulation of this thesis is in reasonable agreement with the measurements... 

RA and transmission techniques [3], and applied it to the studies of LB films of cadmium stearate [3], azobenzene-containing long-chain fatty acids and their barium salts [4], dipalmitoylphosphatidylcholine (DPPC) [5], and polyion complexes [6]. Furthermore, we explored the relationship between the molecular orientation evaluated by this method and pyroelectricity in alternating (noncentrosymmetric) Y-type LB films consisting of a phenylpyrazine-containing long-chain fatty acid and deuterated stearic acid and of their barium salts [7]. 

In the authors laboratory we have studied the fluorescence depolarization of IR-140 in lipid bilayer membranes of L-a-dipalmitoylphosphatidylcholine (DPPC) and observed similar differences between the gel and liquid crystalline phases as has been widely reported for UV/visible probes such as l,6-diphenyl-l,3,5-hexatriene (DPH) in this same medium. Figure 12.4 shows some of these results. 

Entrapment of the enzyme together with the substrate (DNA) in dipalmitoylphosphatidylcholine (DPPC) lipid vesicles. 

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. 

Phospholipid that is the major component of Tung surfactant, and the syndrome caused by its deficiency Dipalmitoylphosphatidylcholine (DPPC, also called dipalmitoyllecithin, DPPL) is the major lipid component of lung surfactant. It is made and secreted by type II granular pneu-mocytes. Insufficient surfactant production causes respiratory distress syndrome, which can occur in preterm infants or adults whose surfactant-producing pneumocytes have been damaged or destroyed. 

Multilamellar liposomes composed of dipalmitoylphosphatidylcholine (DPPC) and dicetyl phosphate (DCP) were prepared by the formation of a thin lipid film and subsequent sonication, and coated with chitosan (Ch) [36], Liposomes with a size of approximately 5 pm were used in the experiment. The Ch-coated and plain liposomes were compared in terms of mucoadhesion to the rat stomach and intestinal parts. Although both the liposomes were less adhesive to the stomach, Ch-coated liposomes displayed much higher mucoadhesion to all the intestinal parts in vitro than the plain liposomes. The intestinal adhesion of the plain liposomes were minimal. Further, Ch-coated liposomes showed a great mucoadhesion to the intestine at acidic and neutral pH values. This was also confirmed by fluorescence microscopy when pyrene-loaded Ch-coated liposomes were used in the mucoadhesion test. 

The quantum yield of photodissociation in neutral aqueous suspension of vesicles like egg lecithin (EL) and dipalmitoylphosphatidylcholine (DPPC) are significantly smaller than in the aqueous solution [83], INpOH (pKa = 9.2, pK a = 0.4) emits only from its DP form (2) in water. On incorporation into liposome membrane, a substantial increase of the P form (1) fluorescence is seen with concomitant decrease of DP form fluorescence. A similar effect is seen for 2NpOH with membrane incorporation. The biexponential fluorescence decay of the P form in fully incorporated naphthol suggests the presence of two localization sites... 

This chapter summarizes the first direct determinations of conformational disorder in phospholipid bilayer systems. The model phospholipid chosen is 1,2 dipalmitoylphosphatidylcholine (DPPC), whose physical properties have been widely investigated for two... 

Another study on this same theme examined the effects of trehalose, glucose and hydroxyethyl starch on the motional properties of the phosphate headgroup of freeze-dried dipalmitoylphosphatidylcholine (DPPC) liposomes, this time employing 31P NMR.110 The work aimed to examine whether there... 

With the objective of designing new compositions of synthetic substitutes for the native lung surfactant, it is desirable to control the physical state and properties of dipalmitoylphosphatidylcholine (DPPC) spread at the air/water interface. DPPC is the main component of the native lung surfactant, which also comprises a complex mixture of lipids and specific proteins [62], Langmuir monolayers provide a model of the air/alveolar interface that is widely used for assessing the properties of lung surfactant replacement compositions. 

Dipalmitoylphosphatidylcholine (DPPC Lipoid, Ludwigshafen, Germany) store at -20°C. 

The two major components of biological membranes are lipids and cholesterol. One major class of lipids are the phospholipids. The H spectrum of one such phospholipid, dipalmitoylphosphatidylcholine (DPPC), in chloroform is shown in Figure 14.28. The H spectrum of cholesterol in chloroform is shown in Figure 14.29 (page 272). 

PL, phospholipids DSPC, disaturated phosphatidylcholine, namely, dipalmitoylphosphatidylcholine (DPPC) in IN and EX, and DPPC plus other disaturated PCs in SU ... 

The use of this simple technique has shed light on the mechanisms by which Azone and oleic acid may exert their well-documented enhancing effects. The study of mixed monolayers of dipalmitoylphosphatidylcholine (DPPC) and Azone or oleic acid (Lewis and Hadgraft, 1990) has revealed, in some detail, possible differences in the way in which these compounds may act as enhancers. Monolayer experiments have also been used to examine the behavior of a complex mixture of lipids (representing those in the stratum comeum) and the way in which these are affected by the presence of Azone (Schuckler and Lee, 1991). Although there are many interesting results in the literature arising from such experiments, it is perhaps these that are the most relevant. Therefore, it is on these results that this section will primarily concentrate. 

A DSC heating scan of a fully hydrated aqueous dispersion of dipalmitoylphosphatidylcholine (DPPC), which has been annealed at 0°C for 3.5 days, is displayed in Fig. 2. The sample exhibits three endothermic transitions, termed (in order of increasing temperature) the subtransition, pretransition, and main phase transition. The thermodynamic parameters associated with each of these lipid phase transitions are presented in Table 1. The presence of three discrete thermotropic phase transitions indicates that four different phases can exist in aimealed, fully hydrated bilayers of this phospholipid, depending on temperature and thermal history. All of these phases are lamellar or bilayer phases differing only in their degree of organization. 

In PC and 1,2-dipalmitoylphosphatidylcholine (DPPC) liposomes below the phase transition temperature, pyrene senses an environment similar to butanol and propanol, respectively, although above the transition temperatures the environment is less polar [49c]. 

Phosphatidylcholine is the major component of endogenous surfactant, constituting about 60% of total phospholipids, and dipalmitoylphosphatidylcholine (DPPC) is the primary surface-tension lowering phospholipid. 

Figure 3.67. AFM image of a dipalmitoylphosphatidylcholine (DPPC) monolayer transferred onto a quartz plate at a surface pressure of 30 mN m. On this hydrophilic substrate the phospholipids have their head groups on the surface. Therefore, the bright spots should correspond to the end-methyl groups of the DPPC hydrocarbon chains. This is corroborated by the finding that the area per bright spot (averaged over many images) corresponds to half of the value for the area per phospholipid molecule as found from the r(A) isotherm at 30 mN m. (Courtesy of X. Zhai and J.M. Kleijn" )...

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