Phopholipids

Although the drug delivery to the lipid bilayer membrane is just the first step for bioactivities and phopholipid vesicles are rather simple in view of the composite structure of biomembranes, the unambiguous specification of the preferential location of the drug is essential the successive processes of the action are expected to be induced via the delivery site in membranes. We expect more advances in the dynamic NMR study, so that we can get insight into the mechanism of DD in membranes. 

D. Small, The Physical Chemistry of Lipids—from Alkanes to Phopholipids, Plenum Press, New York, 1986. 

PAMPA membranes typically consist of phospholipids dissolved in an organic solvent. Both of them affect chemical selectivity. Phospholipids facilitate the permeability of moderately hydrophilic molecules by ionic or hydrogen-bonding interactions (phopholipids are hydrogen bond acceptors). This allows permeation of moderately lipophilic compounds. Recently, it was shown that anionic phospholip-id(s) increases the permeation of basic compounds by ion pair mechanism [54—56]. Many PAMPA variants (and other artificial membrane tools) add anionic phospho-lipid(s) to increase the in vivo predictability. 

There is an emerging literature in MRS in adults with BD, with reports of decreases in dorsolateral prefrontal cortex of neuronal marker NAA (Winsberg et al., 2000) and abnormalities in phopholipid metabolism (Kato et ah, 1995, 1998 Hamakawa et ah, 1999). There is preliminary work to suggest that cortical GABA levels and glutamate turnover are decreased in unipolar depression in adults, but these abnormalities may not be present in bipolar depression (Sanacora et al., 1999, Mason et al., 2000). 

There have been some papers that describe the three regions in the relevant phopholipid-surfactant mixtures (4j. 22j. 23). 

Fate of the remaining chylomicron components After most of tt triacylglycerol has been removed, the chylomicron remnan (which contain cholesteryl esters, phospholipids, apolipoprotein and some triacylglycerol) bind to receptors on the liver (seej 228) and are then endocytosed. The remnants are the hydrolyzed to their component parts. Cholesterol and the nitrogf nous bases of phopholipids (for example, choline) can be req cled by the body. [Note If removal of chylomicron remnants by th liver is defective, they accumulate in the plasma. This is seen i type III hyperlipoproteinemia (also called familial dysbetalipopro teinemia, see p. 229). 

Figure 13.1 Structure of a phospholipid. Phopholipids can have different polar rest groups (R). In addition, the alkyl chains can have different lengths and can be saturated (left chain) or unsaturated (right chain).

The phase behavior of monolayers is determined by the molecular structure of the am-phiphile and the conditions of the subphase. Phospholipids, for example, attract each other because of van der Waals interactions between the alkyl chains. The longer the alkyl chains, the more strongly the phospholipids attract each other. Thus, the LE-LC transition pressure will decrease with increasing chain length (at constant temperature). Double bonds in the alkyl chains increase this phase transition pressure. Charges and oriented dipole moments (see Chapter 6) in the headgroups, lead to a repulsion between the phopholipids and increase the pressure at which the transition occurs. Salts in the subphase, screen this repulsion and decrease the transition pressure. 

FIGURE 13.5 (a) Visualization of a typical multilamellar ethosome containing 2% PL, 30% ethanol, and water by TEM (b) Entrapment of fluorescent probes by phopholipid vesicles as visualized by CSLM. Liposomes (a-c) or ethosomes (d-f) were prepared with one of three fluorescent probes rhodamine red (a, d), D-289 (b, e), or calceine (c, f). White represents the highest concentration of probe. (Reproduced from Touitou, E. et al., J. Control. Release, 65, 403, 2000. With permission from Elsevier.)... 

Froment, M.A., Smith, J., and Freeman, K. 1999. Influence of environmental and agronomic factors contributing to increased levels of phopholipids in oil from UK linseed Linum usitatissimum. Ind. 

FIGURE 7.31. (A) Schematic representation of the bilayer membrane formed by PEE37-b-PEO40 and for comparison a similar representation of a phopholipid bilayer. (B) Dispersion in water of PEE37-b-PEO40 showing next to vesicles, rod-like micelles (grey arrow) and spherical micelles (black arrow). Reproduced with permission of the American Association for the Advancement of Science. 

Fig. 6.11 Schematic representation of initial structures of the DPPC/cho-lesterol and DPPC/cholesterol sulfate membranes. PL phopholipid, CH cholesterol, CS cholesterol sulfate. Left system A, middle system B [73], right DPPC/cholesterol sulfate [75]...

E2. Enholm, C., Shaw, W., Greten, H., and Brown, W. V., Purification from human plasma of a heparin-released lipase with activity against triglyceride and phopholipids. J. Biol. Chem. 250, 6756-6761 (1975). 

Casal, H.L., Mantsch, H.H. 1984. Polymorphic phase behavior of phopholipid membranes studied by infrared spectroscopy. Biochim. Biophys. Acta 779, 382-401. 

Figure 13-3 Quantitative phosphate assay to quantify phopholipids.

Parthasarathy, R., and Eisenberg, F. Jr., 1986, The inositol phopholipids A stereochemical view of biological activity. Biochem. J. 235 313-322. 

Aminophos- Amino-containing phopholipids such as phosphatidyl ethanolamine and... 

Although PG is only a minor phopholipid in animal tissues (1-2% of total phospholipids), it can be a second abundant phospholipid in some lung surfactants at up to 11% of the total (5). 

Resistance to polymyxins. The polymyxins (A, B, C, D, E) are a group of antibiotics obtained from Bacillus polymyxa [145]. Polymyxin E is referred to as colistin. These antibiotics are extremely active against strains of Ps. aeruginosa but have the disadvantage of certain toxicity problems. The action of polymyxin is on the cytoplasmic membrane involving the phopholipid components [65,146]. 

Liposomes are vesicles composed of naturally occurring or synthetic phopholipids. The bilayer structure can be single- or multicompartment. The size can also vary from smaller than 1pm to larger than 10 pm. When negatively charged lipid molecules, which form liposomes, interact with divalent cations, a solid, multilayered, crystallaine structure called cochleate is formed. Because liposomes and cochleates can protect antigens from the GI tract and deliver them to the Peyer s patches, they have been exploited as an effective delivery system for oral vaccination. 

This SPE procedure has been used to achieve partial fractionation of phopholipids by various researchers [2] and, particularly, to recover acidic phospholipids, which can only be eluted from an aminopropyl matrix by changing the ionic strength of the solvent. 

Stewart assay reagent (for determination of phopholipid concentration) For preparation, dissolve 27.03 g of FeCljXdHjO and 30.4 g of NH SCN in 1 L of d.d. H O. The reagent is stored in dark glass bottles at room temperature and used for up to 1 month. 

Several metabolites found in food samples have been estimated using the thermometric approach. These include glucose, cellobiose, lactose, maltose, galactose, lactate, oxalate, phopholipids, ascorbic acid, ethanol, urea [18], xanthine and hypoxanthine [41,42]. Glucose was estimated by co-immobilizing glucose oxidase and catalase [43]. The presence of catalase doubled the thermal... 

Michaelsen and Sorensen used a cholate micellar system for the separation of phopholipids [53], Bjergegaard, et al. compared the separation of 12 flavonoid standards using two surfactant systems CTAB and cholate/taurine [54], Examples of the separation of neutral flavonoid compounds isolated from rape seed leaves using the two surfactant systems were shown (Figure 9). 

There have been many interpretations of the failure to observe a horizontal slope in the isotherms at the main transition.On the other hand, Pallas and Pethica argue that the isotherm in the phopholipid DPPC is horizontal as long as the amphiphile is sufficiently pure and great care is taken in... 

The majority of creams and lotions are emulsions. An emulsion can be defined simply as two immiscible fluids in which one flquid is dispersed as fine droplets in the other. Homogenized milk is an example of a typical oil-inwater (o/w) emulsion. Alilk fat (oil) is dispersed in water as fine droplets by the homogenization process. The reason the fat does not float to the top immediately is due to the presence of emulsifiers in this case, a milk protein called sodium caseinate as well as several phopholipids. In the case of water-in-oil (w/o) emulsions, water is dispersed as droplets and suspended in the oil phase. The nondispersed liquid or external suspending phase is also called the continuous phase. Mayonnaise, vinegar water dispersed as fine droplets in a continuous phase of soybean oil, is an example of a water-in-oil emulsion. Lecithin from eggs stabilizes the mayonnaise emulsion. 

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