Phosphatidylethanolamine , phase

Amphiphilic Molecules. In just about all cases of lyotropic Hquid crystals, the important component of the system is a molecule with two very different parts, one that is hydrophobic and one that is hydrophilic. These molecules are called amphiphilic because when possible they migrate to the iaterface between a polar and nonpolar Hquid. Soaps such as sodium laurate and phosphoHpids such as a-cephalin [5681-36-7] (phosphatidylethanolamine) (2) are important examples of amphiphilic molecules which form Hquid crystal phases (see Lecithin Soap). 

Koryta et al. [48] first stressed the relevance of adsorbed phospholipid monolayers at the ITIES for clarification of biological membrane phenomena. Girault and Schiffrin [49] first attempted to characterize quantitatively the monolayers of phosphatidylcholine and phos-phatidylethanolamine at the ideally polarized water-1,2-dichloroethane interface with electrocapillary measurements. The results obtained indicate the importance of the surface pH in the ionization of the amino group of phosphatidylethanolamine. Kakiuchi et al. [50] used the video-image method to study the conditions for obtaining electrocapillary curves of the dilauroylphosphatidylcholine monolayer formed on the ideally polarized water-nitrobenzene interface. This phospholipid was found to lower markedly the surface tension by forming a stable monolayer when the interface was polarized so that the aqueous phase had a negative potential with respect to the nitrobenzene phase [50,51] (cf. Fig. 5). 

Marsh, D. (1991). Analysis of the chainlength dependence of lipid phase transition temperatures main and pretransitions of phosphatidylcholines main and non-lamellar transitions of phosphatidylethanolamines, Biochem. Biophys. Acta-Biomembranes, 1062, 1-6. 

The hydroperoxides of various phospholipids, such as phosphatidylcholine (PC— OOH, 155), phosphatidylserine (PS—OOH), phosphatidylethanolamine (PE—OOH), phos-phatidylinositol (PI—OOH) and cardiolipin (CL—OOH), can be determined by HPLC-ELD on a polar LC—NH2 column, using as mobile phase a MeOH//-PrOH/40 mM aqueous NaH2P04 mixture (61 30 9 by volume). ELD is by the hanging Hg drop electrode method set at —150 mV vs. SCSE. The relative mobility for the given chromatographic system is shown in equation 68, which is almost a reversal of the order shown in equation 63 for HPTLC. The LOD varies from about 0.5 to 1.0 pmol, depending on the class of phospholipid hydroperoxide . ... 

Figure 1. Proton magnetic resonance spectra of dimyri-stoyl-m -phosphatidylethanolamine at different temperatures, showing onset of mesomorphic phase (9)...

Figure 8-12 (A) 31P NMR spectra of different phospholipid phases. Hydrated soya phosphatidylethanolamine adopts the hexagonal Hn phase at 30°C. In the presence of 50 mol% of egg phosphatidylcholine only the bilayer phase is observed. At intermediate (30%) phosphatidylcholine concentrations an isotropic component appears in the spectrum. (B) Inverted micelles proposed to explain "lipidic particles" seen in freeze fracture micrographs of bilayer mixture of phospholipids, e.g., of phosphatidylethanolanine + phosphatidylcholine + cholesterol. From de Kruijft et al.m Courtesy of B. de Kruijft.

Siegel DP, Epand RM (1997) The mechanism of lamellar-to-inverted hexagonal phase transitions in phosphatidylethanolamine implications for membrane fusion mechanisms. Biophys J 73 3089-3111... 

As stated, biological membranes are normally arranged as bilayers. It has, however, been observed that some lipid components of biological membranes spontaneously form non-lamellar phases, including the inverted hexagonal form (Figure 1.9) and cubic phases [101]. The tendency to form such non-lamellar phases is influenced by the type of phospholipid as well as by inserted proteins and peptides. An example of this is the formation of non-lamellar inverted phases by the polypeptide antibiotic Nisin in unsaturated phosphatidylethanolamines [102]. Non-lamellar inverted phase formation can affect the stability of membranes, pore formation, and fusion processes. So-called lipid polymorphism and protein-lipid interactions have been discussed in detail by Epand [103]. 

Fig. 3.47 Phase diagrams of flunarizine-dielaidoylphospholipid mixtures, (a) Phosphatidylcholine, (b) phosphatidylethanolamine, and (c) phosphatidylserine. (Reprinted from Fig. 3 of ref. 150 with permission from Academic Press.)...

Seddon, J.M., Cevc, G., and Marsh, D. (1983) Calorimetric studies of the gel-fluid transition (Lj) —> La) and lamellar-inverted hexagonal (La — H ) phase transition in dialkyl- and diacyl-phosphatidylethanolamines. Biochemistry 22 1280-1289. 

As before, the phosphatidylethanolamine sample in chloroform-methanol (1 10, v/v) is treated with 0.5 N NaOH in methanol for 20 min at room temperature. The reaction is stopped by the addition of an equivalent amount of 6 N HCI. Subsequent extraction of the mixture by the Bligh-Dyer method will ultimately yield a chloroform soluble fraction (containing the methyl esters) and a water-soluble phase (containing the glycerophosphoethanola-mine). Under these conditions, the reaction is usually quantitative this can be... 

Lin, J. T., and McKeon, T. A. 2003. Relative retention times of the molecular species of acylglycerols, phosphatidylcholines and phosphatidylethanolamines containing ricinoleate in reversed-phase HPLC. /. Liquid Chromatogr. Rel. Technol., 26, 1051-1058. 

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