Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: CAS:18194-24-6 (DMPC)
 1,152 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Spin-label electron spin resonance (ESR) spectroscopy and spectrophotometry at fixed wavelength are used to study fully hydrated aqueous dispersions of phosphatidylcholines (PCs) with poly(ethylene glycol:2000)-phosphatidylethanolamines (PEG:2000-PEs). PEG:2000-PE is a micelle-forming polymer-lipid that is extensively used for increasing the lifetime of PC liposomes in the blood circulation through a steric stabilisation effect. The PC lipids and the PEG:2000-PE polymer-lipids have the same acyl chain length of either dimiristoyl (DM) or distearoyl (DS) chains. DMPC/PEG:2000-DMPE and DSPC/PEG:2000-DSPE mixtures were investigated over the entire range of relative compositions (0-100 mol%). In both dispersions, the low-temperature conventional spin label ESR spectra and the temperature dependence of the absorbance at 400 nm give an indication of the conversion from lamellae to micelles with increasing PEG:2000-PEs content. The physical state of the lipid assemblies, lamellar or micellar, is dependent not only on PEG:2000-PEs content, but also on the length of hydrocarbon chain of the lipid matrix. Micellisation is attained more readily in dispersions with longer hydrocarbon chains (i.e. in DSPC/PEG:2000-DSPE mixtures) than in those with shorter acyl chains (i.e. in DMPC/PEG:2000-DMPE mixtures). Saturation transfer ESR (ST-ESR) and absorbance measurements reflect the disaggregation of the bilayers and a reduction in the size of the lipid aggregates by PEG:2000-PEs at low content.
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PMID:Lipid chain length effect on the phase behaviour of PCs/PEG:2000-PEs mixtures. A spin label electron spin resonance and spectrophotometric study. 1160 13

The antitumor platinum(II) compound, [Pt(dach)(Glu)] (dach=trans(+/-)-1,2-diaminocyclohexane, Glu=glutamate) was formulated with a stealth liposome to improve its biological activity. Liposomes were composed of PC/PEG2000-PE/CH (PC=1,2-diacyl-glycero-3-phosphocholine; PEG2000-PE=poly(ethylene glycol)2000-1,2-diacyl-glycero-3-phosphoethanolamine; CH=cholesterol) involving different acyl moieties of phospholipids such as DO (dioleoyl), DM (dimyristoyl) or DS (distearoyl) group. Among the different acyl groups in the stealth liposomes, the DM formulation was optimal for the preparation of the liposomal [Pt(dach)(Glu)] at the mole ratio of DMPC/PEG2000-DMPE/CH=50/5/45 and at the weight ratio of drug/lipid=1/20, which is represented as L-[Pt(dach)(Glu)]. In vitro cytotoxicity was examined in sensitive A2780 and ME180 and their cisplatin-resistant A2780/PDD and ME180/PDD cancer cells. L-[Pt(dach)(Glu)] was 2 approximately 3 times more cytotoxic than the free complex [Pt(dach)(Glu)] and cisplatin in sensitive cells, and 4 approximately 8 times more cytotoxic in resistant cells. Thus, the resistance index of L-[Pt(dach)(Glu)] was 1.3 approximately 2 while those of the free complex and cisplatin were 5 approximately 6, which indicates that L-[Pt(dach)(Glu)] overcome the cisplatin resistance in both resistant cells. In vivo antitumor activity was assayed against the L1210/S leukemia. The optimal activities (% T/C) of the free complex and L-[Pt(dach)(Glu)] were >459/20 and >442/200 mg/kg, respectively. Considering the amount of the platinum complex in L-[Pt(dach)(Glu)], the liposomal [Pt(dach)(Glu)] displayed 2-fold higher drug potency than the free complex. The biodistribution experiment using LE52 tumor-bearing mouse showed excellent lung targeting property of L-[Pt(dach)(Glu)].
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PMID:Enhanced antitumor activity [correction for activitiy] of trans(+/-)-1,2-diaminocyclo- hexaneglutamatoplatinum(II) formulated with stealth liposome. 1464 89

The biggest challenge to improve extracorporeal circulation (ECC) circuits lays on avoiding platelet adhesion to their surfaces, because this contributes to thrombus formation, resulting in the activation of blood coagulation. One approach to minimize this effect is to improve the biocompatibility of ECC circuits by modifying their surfaces. This can be achieved by coating them with heparin or phospholipids. The present study investigated the adhesion and morphology characteristics of fibroblastic and blood cells cultured on uncoated poly (vinyl) chloride PVC tubes as well as on heparin, phosphatidylcholine (DMPC), and phosphatidylethanolamine (DMPE) -coated tubing. The results showed the importance of uniform coating regardless of the substance used, because the coatings cover the grooves on PVC surfaces, which favor cell adhesion. The comparison among the three different coatings showed the best biocompatibility results for the PVC tubes coated with heparin, followed by the coating with DMPE and with DMPC. For all coated tubes, cells did not spread on the PVC surfaces and, consequently, did not adhere to their surfaces, increasing the overall biocompatibility of PVC tubes. However, possible DMPE's alkylation, caused by sterilization, resulted in increased material hydrophobicity, which explains the decrease in fibroblastic adhesion. Furthermore, sterilization of DMPC-PVC improves its hydrophilic character, also decreasing adhesion. Based on these results, coating PVC with the phospholipids DMPC and DMPE seems to be a promising technique to improve the biocompatibility of PVC tubes, and is worthy of further investigation.
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PMID:Analysis of cellular morphology, adhesion, and proliferation on uncoated and differently coated PVC tubes used in extracorporeal circulation (ECC). 1501 8

Density-dependent spectrin binding to dimyristoylphosphatidylcholine/dimyristoylphosphatidylethanolamine (DMPC/DMPE) small uni-lamellar vesicles (SUVs) has been directly evaluated in this work from the increase in the extent of quenching of the tryptophan fluorescence of spectrin at two different temperatures, above and below the main phase transition temperatures (Tm). Results from the binding studies of spectrin to phospholipid SUVs indicated that the binding dissociation constant Kd, increased from 45 +/- 7 nM in pure DMPC SUVs to 219 +/- 20 nM in DMPC/DMPE (50:50) SUVs, both in the gel and liquid crystalline phase. However, in pure DMPE SUVs the Kd decreased drastically to 0.7 +/- 0.2 nM in the gel phase at 18 degrees C and to 2.6 +/- 0.7 nM in the fluid phase at 55 degrees C indicating a high affinity binding of spectrin for the bilayer-forming DMPE. The maximum extent of phospholipid-induced quenching and the number of spectrin molecules associated with one SUV particle, evaluated in the present work, led to a model in DMPC/DMPE bilayer membranes indicating the PE-binding site of spectrin to localize at one of the terminal domains of the dimeric spectrin. A direct evidence of the localization of the PE-binding site at one of the terminal ends of the spectrin dimer also came from electron microscopic observation in fluid membranes made of bovine brain PE.
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PMID:Membrane interaction of erythroid spectrin: surface-density-dependent high-affinity binding to phosphatidylethanolamine. 1520 38

Using small-angle neutron scattering (SANS) and cyclic voltammetry (CV), we show that model biological membranes can be deposited on a polymer cushion confined in highly regular porous alumina. The thicknesses of the dilute polymer cushion chemically bound to the alumina and of the supported bilayer are obtained for two polyethylene glycol cushions (PEG(5000) and PEG(20000)) and for a cushion made of chains bearing a lipid anchor at their free end (DSPE-PEG(3400)). The bilayers are studied well below and well above the chain melting temperature of the lipid mixture (DMPC/DMPE: 80/20), using a coenzyme (Ubiquinone, UQ(10)) as a redox probe for the voltammetry experiments. Analysis of the SANS form factor of the bilayers shows that the bilayer thickness can be extracted in this particular geometry. Using PEG chains grafted at a low surface density (D < 2R(g)), the thickness of the complete molecular construction is obtained by CV, which shows (after subtracting the bilayer thickness) that the polymer cushion thickness can be varied from 50 to 150 Angstroms. The values obtained with three different chain lengths, are in perfect agreement with the radius derived from the Flory theory.
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PMID:Polymer-cushioned lipid bilayers in porous alumina. 1553 66

A microscopic study has allowed the analysis of modifications of various shapes acquired by phospholipid vesicles during a hydrostatic pressure treatment of up to 300 MPa. Giant vesicles of dimyristoylphosphatidylcholine / phosphatidylserine (DMPC/PS) prepared at 40 degrees C mainly presented a shape change resembling budding during pressure release. This comportment was reinforced by the incorporation of 1,2-dioleyl-sn-glycero-3-phosphatidylethanolamine (DOPE) or by higher temperature (60 degrees C) processing. The thermotropic main phase transition (L alpha to P beta') of the different vesicles prepared was determined under pressure through a spectrofluorimetric study of 6-dodecanoyl-2-dimethylamino-naphtalene (Laurdan) incorporated into the vesicles' bilayer. This analysis was performed by microfluorescence observation of single vesicles. The phase transition was found to begin at about 80 MPa and 120 MPa for DMPC/PS vesicles at, respectively, 40 degrees C and 60 degrees C. At 60 degrees C the liquid-to-gel transition phase was not complete within 250 MPa. Addition of DMPE at 40 degrees C does not significantly shift the onset boundary of the phase transition but extends the transition region. At 40 degrees C, the gel phase was obtained at, respectively, 110 MPa and 160 MPa for DMPC/PS and DMPC/PS/DOPE vesicles. In comparing volume data obtained from image analysis and Laurdan signal, we assume the shape change is a consequence of the difference between lateral compressibility of the membrane and bulk water. The phase transition contributes to the membrane compression but seems not necessary to induce shape change of vesicles. The high compressibility of the L alpha phase at 60 degrees C allows induction on DMPC/PS vesicles of a morphological transition without phase change.
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PMID:Pressure-induced shape change of phospholipid vesicles: implication of compression and phase transition. 1624 32

Monolayers spread on Hg drops are shown as a suitable experimental set up to study the influence of external electric fields on the structure of lipid membranes. The electrical response exhibits a sharp transition at 24 degrees C, the transition temperature of DMPC. In addition, voltammetric response of monolayers of mixtures of DMPC/DMPE adsorbed on mercury, shows a similar trend to that found for dipole potential of monolayers of the same composition spread on an air-solution interface. It is concluded that a lipid monolayer adsorbed in a mercury-solution interface, has comparable properties as those found in other experimental models of lipid membranes in similar conditions. In addition, they constitute an ideal set up to study the effect of electrical fields on the dynamic conformation of lipids as a function of packing change produced by the condensation in the gel state or by the interaction of polar head groups.
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PMID:Lipid monolayers on Hg as a valid experimental model for lipid membranes under electrical fields. 1641 3

Changes in the thermal behavior of DMPC (dimyristoyl-r-phosphatidylcholine) and an equimolar mixture of DMPC and DMPE (dimyristoyl-L-phosphatidylethanolamine) induced by the plant hormone abscisic acid (ABA) have been investigated using fluorescent probes. The fluorescence decay of the hydrophobic probe 1,6-diphenyl-1,3,5-hexatriene (DPH) in these vesicles has been measured using frequency-domain fluorometry, and has been analyzed using both models of discrete exponential components and continuous lifetime distributions. In the DMPC vesicles, using the distributional approach, higher center and width values were observed in the presence of abscisic acid (ABA), indicating a decrease in the dielectric constant of the lipid phase that we attribute to a decrease in the water concentration within the bilayer. Moreover, the presence of ABA in the liposomes increased the phospholipid phase transition temperature. The addition of ABA to the DMPC/DMPE mixture strongly increased the microheterogeneity of the system as reported by the FWHM (full-width at half-maximum) of the distributional approach.
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PMID:Abscisic acid-induced microheterogeneity in phospholipid vesicle: a fluorescence study. 1705 22

Polyethylene glycol (PEG)-conjugated lipids are commonly employed for steric stabilization of liposomes. When added in high concentrations PEG-lipids induce formation of mixed micelles, and depending on the lipid composition of the sample, these may adapt either a discoidal or a long threadlike shape. The factors governing the type of micellar aggregate formed have so far not been investigated in detail. In this study we have systematically varied the lipid composition in lipid/PEG-lipid mixtures and characterized the aggregate structure by means of cryo-transmission electron microscopy (cryo-TEM). The effects caused by adding sterols, phosphatidylethanolamines, and phospholipids with saturated acyl chains to egg phosphatidylcholine/1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine-N-[methoxy(polyethylene glycol)-2000 (EPC/DSPE-PEG2000) mixtures with a fixed amount (25 mol %) of DSPE-PEG2000 was studied. Further, the aggregate structure in 1,2-dimyristoyl-sn-glycero-3-phosphatidylcholine/1,2-dimyristoyl-sn-glycero-3-phosphatidylethanolamine-N-[methoxy(polyethylene glycol)-2000] (DMPC/DMPE-PEG2000) samples above and below the gel to liquid crystalline phase transition temperature (TC) was investigated. Our results revealed that lipid components, as well as environmental conditions, that reduce the lipid spontaneous curvature and increase the monolayer bending modulus tend to promote formation of discoidal micelles. At temperatures below the gel-to-liquid crystalline phase transition temperature reduced lipid/PEG-lipid miscibility, furthermore, likely contribute to the observed formation of discoidal rather than threadlike micelles.
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PMID:Structure of mixed micelles formed in PEG-lipid/lipid dispersions. 1734 1

Foam thin liquid films (TLF) and monolayers at the air-water interface formed by DMPC mixed with DMPE-bonded poly (ethylene glycol)s (DMPE-PEG(550), DMPE-PEG(2000) and DMPE-PEG(5000)) were obtained. The influence of both (i) PEG chain size (evaluated in terms of Mw) and mushroom-to-brush conformational transition and (ii) of the liposome/micelle ratio in the film-forming dispersions, on the interfacial properties of mixed DMPC/DMPE-PEG films was compared. Foam film studies demonstrated that DMPE-PEG addition to foam TLFs caused (i) delayed kinetics of film thinning and black spot expansion and (ii) film stabilization. At the mushroom-to-brush transition, due to steric repulsion increased DMPE-PEG films thickness reached 25 nm while pure DMPC films were only 8 nm thick Newton black films. It was possible to differentiate DMPE-PEG(2000/5000) from DMPE-PEG(550) by the ability to change foam TLF formation mechanism, which could be of great importance for "stealth" liposome design. Monolayer studies showed improved formation kinetics and equilibrium surface tension decrease for DMPE-PEG monolayers compared with DMPC pure films. SEM observations revealed "smoothing" and "sealing" of the defects in the solid-supported layer surface by DMPE-PEGs adsorption, which could explain DMPE-PEGs ability to stabilize TLFs and to decrease monolayer surface tension. All effects in monolayers, foam TLFs and solid-supported layers increased with the increase of PEG Mw and DMPE-PEG concentration. However, at the critical DMPE-PEG concentration (where mushroom-to-brush conformational transition occurred) maximal magnitude of the effects was reached, which only slightly changed at further DMPE-PEG content and micelle/liposome ratio increase.
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PMID:Effects of poly (ethylene glycol) chains conformational transition on the properties of mixed DMPC/DMPE-PEG thin liquid films and monolayers. 1758 56


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