Phospholipids zwitterionic

Phospholipids. For the removal of ionic contaminants from raw zwitterionic phospholipids, most lipids were purified twice by mixed-bed ionic exchange (Amberlite AB-2) of methanolic solutions. (About Ig of lipid in lOmL of MeOH). With both runs the first ImL of the eluate was discarded. The main fraction of the solution was evaporated at 40°C under dry N2 and recryst three times from n-pentane. The resulting white powder was dried for about 4h at 50° under reduced pressure and stored at 3°. Some samples were purified by mixed-bed ion exchange of aqueous suspensions of the crystal/liquid crystal phase. [Kaatze et al. J Phys Chem 89 2565 7955.]... 

The Electrical Potential Distribution at the ITIES in the Presence of Zwitterionic Phospholipids... 

FIG. 9 Simulated electrical potential and space charge density profiles at the water-1,2-DCE interface polarized at/= 5 in the absence (a) and in the presence (b) of zwitterionic phospholipids. The supporting electrolyte concentrations are c° = 20 mM and c = 1000 mM. The molecular area of the phospholipids is 150 A, and the corresponding surface charge density is a = 10.7 xC/cm. The distance between the planes of charge associated with the headgroups is d = 3 A. 

FIG. 10 Simulated enhancement factor for monolayers of zwitterionic phospholipids with different molecular areas (shown on the curves) at the polarized water-1,2-DCE interface. The supporting electrolyte concentrations are c° = 20 mM and c" = 1000 mM. 

The GIT has about 13% wt/wt negatively charged lipid-to-zwitterionic phospholipid ratio. It is about twice as large in the BBB. Factoring this into the in vitro model is expected to be important. 

Scheme 3.5, and carotenoids have been previously incorporated into vesicles of phospholipids, Figure 3.1 (Milon et al. 1986, Britton 1998). It was therefore reasonable to connect carotenoids with a phosphate group, above all because hydrophobic phosphate esters had previously been synthesized (Sliwka 1997). The C30-monoglyceride, 3.12, was therefore used as an educt for the synthesis of the zwitterionic, hydrophobic C30-lysophosphocholine, 3.15, via aminolyse of the bromo phosphoester,... 

Phosphatidylcholine (PC) is widely used in liposomes, and at physiological pH has a zwitterionic structure, is only slightly able to form salts with divalent cations such as Ca2+, and has a lower transition temperature from liquid to crystalline than other phospholipids. 

Fig. 22. Schematic representation of transmembrane electron transfer from a reducing agent (such as sodium dithiomte) to an oxidizing agent (such as potassium ferricyanide) by a zwitterionic caroviologen such as 99 incorporated in the bilayer membrane of a phospholipid vesicle [8.143].

The interactions of TDZ (6) with model membranes composed of different phospholipids were also studied by the same group [78]. Calorimetric studies demonstrated that TDZ (6) altered the thermotropic properties of negatively charged DMPC membranes to a larger extent than of zwitterionic phospholipids (PC and PE). The character of the drug-induced changes of the transition parameters of all studied lipids indicated that TDZ (6), similarly to other phenothiazine derivatives, was likely to be localized close to the po-lar/apolar interface of the bilayers. Experiments in which fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH) was employed revealed that TDZ (6) reduced the mobility of lipid molecules in a concentration-dependent manner and thus decreased membrane fluidity. The influence of TDZ (6) on isolated... 

A later publication from the same group [153] reporting on 31P- and 2H-NMR and DSC studies on zwitterionic and anionic phospholipids in the absence and presence of doxombicin (adriamycin) described different results [152], Doxorubicin had a stronger disordering effect on the membrane of lipid mixtures enriched with anionic lipids. However, extensive segregation of DOPE and DOPA or DPS was not observed even under conditions of Hlrphase formation . According to the authors, the reason for this discrepancy was that in the earlier paper the phase separation was obtained with membranes subject to gel-liquid crystalline phase transition , which was, however, discounted in the first paper. 

Several studies have been performed to analyze the effect of membrane composition on accumulation and transport of antineoplastic drugs. In particular, the role of anionic lipids in transport and passive diffusion, as well as on the binding of doxorubicin and its effect on the degree of order of lipid acyl chains was investigated. Using 2H-NMR spectroscopy the effect of doxorubicin on mixed bilayers of DOPS, DOPA, dioleoylphosphatidylcholine (DOPC), and DOPE was studied. It was found that doxorubicin does not affect acyl chain order of pure zwitterionic phospholipids but dramatically influences that of anionic lipids [112]. At 25 °C, in bilayers consisting of 67... 

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