Dipalmitoyl-phosphatidylethanolamine

In a typical experiment, Israelachvili deposited monolayers of surfactants onto cleaved mica sheets, and evaluated the surface energies using the JKR equation. Fig. 11 contrasts results for mica coated with monolayers of (a) L-a-dipalmitoyl-phosphatidylethanolamine (DMPE) where j/a = = 27 mJ/m and (b) hexa-decyltrimethylammonium bromide (CTAB) where = 20 mJ/m and = 50 mJ/m. ... 

The next development on water-oil isotherms was presented by Mohwald s group at the Max-Planck Institute in Berlin [21,22]. They investigated monolayers of dipalmitoyl phosphatidylethanolamine (DPPE) at interfaces of water and hydrocarbons -dodecane (C]2, -hexadecane (Cig), and bicyclohexyl (BCH). The transition pressure was increased and the molecular area at transition decreased in the order Cig—C12 BCH. Also the heat of transition was decreased in the same order, and was more strongly decreasing with... 

Figure 2 Structure of functionalized anchors and heterobifunctional reagents. DPPE is given as an example. Abbreviations DPPE, l,2-dipalmitoyl-sn-glycero-3-phos-phoethanolamine DPPE-AcBr, bromoacetyl dipalmitoyl phosphatidylethanolamine.

Brennan et al. used a method to detect the reaction of acetylcholineesterase with acetylcholine [46]. The method was based on the use of a monolayer, consisting of fatty acids having Ci6 chain lengths, which were covalently attached to quartz wafers and which contained a small amount of nitrobenzoxadiazole dipalmitoyl phosphatidylethanolamine (NBD-PE) (partitioned from water into the membrane). The enzyme substrate reaction produced a decrease in fluorescence intensity from the monolayer, and the detection system was sensitive to the changes in bulk concentration of as small as 0.1 pM, with a limit of detection of 2 pM of acetylcholine. The mechanism of transduction of the enzymatic reaction was investigated using spectrofluorimetric methods and fluorescence microscopy. 

Lecithins as antioxidants. The literature is replete with references to the antioxidant properties of lecithins. For example, Pokomy (102) claimed that the addition of soybean phospholipids reduced the rate of autoxidation of sunflower oil and prolonged the induction period. Hudson and Ghavani (103) published data showing that the addition of 0.3% dipalmitoyl phosphatidylethanolamine (DPE) to refined soybean oil increased the induction time during Rancimat analysis from 8.8 hours to 19.3 hours. Hildebrand et al. (104), and Jung et al. (105), also published data demonstrating the antioxidant properties of various phospholipids and commercial lecithins. 

Fig. 9. Temperature-composition isobaric phase diagram for the fully hydrated dipal-mitoylphosphatidylcholine/dipalmitoyl-phosphatidylethanolamine system constructed using the temperature gradient method. The notation used is that of Luzzati [8] and is as follows Lc, lamellar crystalline (also referred to as the subgel phase) L f, lamellar gel phase with hydrocarbon chains tilted with respect to the bilayer normal P)el, ripple phase L. lamellar liquid crystal phase. Insert bold line in graph as indicated...

Figure Bl.20.11. Force curves of DMPC/DPPE (dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylethanolamine) bilayers across a solution of PEG at different concentrations. Clearly visible is a concentration-dependent depletion attraction, with permission from [17]. 

Water-soluble fusogens. Large decreases of the surface potential were observed when dipalmitoylphosphatidylcholine (dpPC) was spread on subphases containing glycerol, dimethyl sulphoxide, sucrose, sorbitol or poly(ethyleneglycol) of M.W. 1500 6000 3 x 10 or 5 X 10 (Fig, 1). Similar results were obtained for dipalmitoyl-phosphatidylethanolamine (dpPE). 

Caccialanza, G., C. Gandini, M. Kitsos, G. Massolini, LC analysis of phospholipids in washings from rabbit eustachian tube dipalmitoyl phosphatidylethanolamine content, J. Pharm. Biomed. Anal., 1989, 7, 1931—1935. 

Materials. Egg phosphatidylcholine (PC), bovine brain phosphatidylserine (PS) were obtained from Avanti Polar Lipids Inc. (Birmingham, AL) and cholesterol was from Sigma (St. Louis, MO). Ganglioside GMj, bovine, was obtained from Calbiochem (San Diego, CA). Diethylenetriamine pentaacetic acid distearylamide complex (DPTA-SA) was synthesized according to ref. 17 and nlIn-DTPA-SA was prepared as described (7). This lipophilic radiolabel is not transferred to the serum components from liposomes (unpublished data), nor is it rapidly metabolized in vivo (7). The synthesis of N-(glutaryl)phosphatidylethanolamine(NGPE) has been described (18). Dipalmitoyl deoxyfluorouridine(dpFUdR) was synthesized as described (24). 

In the above subsection it was demonstrated that the inclusion of electrostatic interactions into the pressure-area-temperature equation of state provides a better fit to the observed equilibrium behavior than the model with two-dimensional neutral gas. Considering this fact, we would like to devote our attention now to the character of the lipid film under the dynamical, nonequilibrium conditions. In the following we shall describe the dynamical behavior of the phospholipid(l,2-dipalmitoyl-3-sn-phosphatidylethanolamines DPPE) thin films in the course of the compression and expansion cycles at air/water interface. 

Figure 3 Design of a diepitope liposomal construct. Small unilamellar liposomes (PC/PG/Chol 55/25/50 molar ratio diameter 100nm) containing 10mol% of bromo-acetyl l,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine and 10mol% of the thiol-reactive lipopeptide adjuvant anchor Pam3CysAlaGly-Mal were reacted, at 25°C successively at pH 6.5, with the T-helper epitope QYI, derivatized with a C-linker at its N-terminus, followed at pH 9.0 by the B-epitope TPE derivatized with a CG linker at its N-terminus. Abbreviations PC, phosphatidylcholine PE, phosphatidylethanolamine SUV, small unilamellar vesicles. Source From Refs. 11, 20, 21.

The major (salvage) pathways for the formation of phosphatidylcholine and ethanolamine are illustrated in Figure 19.16. Free (dietary) choline and etha-nolamine are converted to their CDP derivatives, which then react with diacyl-glycerol to form phosphatidylcholine and ethanolamine. In the lungs, another pathway forms dipalmitoyl phosphatidylcholine, a powerful surfactant. Phos-phatidylethanolamine may be methylated by S-adenosylmethionine (SAM see Chapter 20) to yield phosphatidylcholine. The reaction is catalyzed by two enzymes the first methyl group is transferred via phosphatidylethanolamine N-methyltransferase I. The other two methyl groups are transferred by phosphatidylethanolamine N-methyltransferase II. Some authorities believe that the two enzymes are identical. It has also been proposed that methylation of phospha-... 

The construction of biomembrane systems from polymers containing phosphatidylethanolamine and -choline analogues in the side chains by spreading at the air/water interface and by the Langmuir-Blodgett technique is of great interest [5,101,249,250]. Eor instance, multilayers of dipalmitoyl-DL-a-phosphatidylethanol methacrylamide polymerized imder y radiation resemble a natural phosphoHpid structure and show a fine lamellar structure with a periodicity the average monolayer was estimated to be 32 A thick [251]. 

L-a-Dioleoyl Phosphatidylethanolamine (DOPE), and 1,2-Dipalmitoyl-OT-Glycero-3-Phosphocholine (DPPC) were purchased from Avanti Polar Lipids. The chol-PEGjj was obtained in one step from the reaction of cholesteryl chloroformate and a-amino-co-methoxy-PEG. The luciferase encoding gene was obtained as reported (22). Picogreen was purchased from Molecular Probes, USA, Baftlomycin from Sigma, France, the BCA kit from Pierce and the luciferase kit from Promega. 

Lipids with L-a-phosphatidylethanolamine derivatives with spermidines 1,2-dipalmitoyl-pho sphatidy lethanolamido spermine(DPPES) (116) or L-a-phosphatidylcholine with phos-phonate diester (127,128). 

Abbreviations DMPC, DPPC, DSPC, dimyristoyl-, dipalmitoyl-,distearoyl-phosphatidylcholine DPPA, dipalmitoylphosphatidic acid PE, phosphatidylethanolamine PS, phosphatidylserine (U) and (M), unilamellar and multilamellar liposomes temperature of crystal liquid-crystal transition Diff. spectr., difference spectroscopy. 

Fig. 5. Synthesis of the diastereomers of dipalmitoyl [>K),i>0]phosphatidylethanolamine reported by Bruzik and Tsai (1982).

---