Vesicles dimyristoylphosphatidylcholine

Conformational changes in BmorPBP were also studied in the presence of model membranes using CD spectroscopy. Conformational changes more pronounced than those observed at low pH were detected in the presence of anionic vesicles of dimyristoylphosphatidylglycerol (DMPG), whereas the effect of neutral phospholipids vesicles, dimyristoylphosphatidylcholine (DMPC) was... 

Eftink, M. R., Puri, R. K. and Ghahramani, M. D. (1985). Local anesthetic-phospholipid interactions. The pH-dependence of the binding of dibucaine to dimyristoylphosphatidylcholine vesicles, Biochim. Biophys. Acta, 813, 137-140. 

Chronocoulometry and photon polarization modulation infrared reflec-tion/absorption spectroscopy have been employed [311] to study the fusion of dimyristoylphosphatidylcholine vesicles onto an Au(lll) electrode. The fusion was controlled either by the electrode potential, or charge. Film characteristics was also potential dependent. After removing the film from the electrode surface (negative potential), phospholipid molecules remained in its close proximity, in the ad-vesicle state. Several electrochemical and nonelec-trochemical methods have been applied [312, 313] to investigate the spreading of small unilamellar vesicles onto Au(lll) electrode. Vesicles fused onto the surface at > —0.5 V (versus SSCE), to form defected bilayers in contact with the metal surface. At more negative potentials, the film was removed from the electrode surface, but it still remained in its close proximity. 

Experimental demonstration that the enzyme inside dimyristoylphosphatidylcholine (DMPC) vesicles was active against externally added ADP, yielding lipid vesicle trapped poly (A). 

Organic-soluble lanthanide chelates have been used to probe lipophillic systems. The compound 4-(4-dipentylamino-( )- S-styryl)-l-(2,2,2-trifluoroethyl)pyridinium perchlorate (22) was employed as a probe in dimyristoylphosphatidylcholine vesicles. Probe molecules assembled in the inner and outer shells of the vesicle as evidenced by the presence of two signals in the NMR spectrum (376 MHz). Even though addition of Eu(fod)3 promoted vesicle fusion, only one of the signals shifted. The shifted signal was likely from the probe molecule on the outer shell, as the internal P signal of the phospholipid did not shift in the presence of Eu(fod)3 ". 

In 1991, Johnson et al. reported one of the first NR studies of phospholipid bilayers at the solid-solution interface [46]. Although these measurements were not the first to employ NR to study molecules adsorbed at the solid-hquid interface, they did constitute the first measurements of a supported bilayer using NR. A bilayer of dimyristoylphosphatidylcholine (DMPC) was spread on a quartz surface by the fusion and rupturing of smaU unilamellar vesicles. The very smooth, singlecomponent substrate aUowed a complex model of the interface to be constructed from layers corresponding to (i) the quartz, (ii) a thin film of water on the quartz... 

Dimova, R., Pouligny, B., and Dietrich, C. (2000) Pretransitional effects in dimyristoylphosphatidylcholine vesicle membranes optical dynamometry study. Biophysical Journal, 79 (1), 340-355. 

In a vesicle an aqueous volume (water pool) is entirely enclosed by a membrane that is basically a bilayer of lipid molecules [127-137]. In the case of the unilamellar dimyristoylphosphatidylcholine (DMPC) vesicles (radius = 250 nm) there is only one such bilayer, whereas a multilamellar vesicle (radius 1000 nm) consists of several concentric bilayers. Unilamellar vesicles can be produced from multilamellar vesicles by sonication. In such a system there are two kinds of... 

Incorporation of zeaxanthin, astaxanthin, and their C50 homologues into dimyristoylphosphatidylcholine vesicles. Helv ChimActa69 12-24... 

Amphotericin B is complexed with deoxycholate (C-AMB) and marketed as a lyophilized powder (fungizone) containing 50 mg of amphotericin B that forms a colloid in water. Three lipid formulations of amphotericin B are marketed in the U.S. Amphotericin B colloidal dispersion (ABCD, AMPHOTEC, amphocil) contains equimolar amounts of amphotericin B and cholesteryl sulfate. AMBISOME is a small, unilamellar vesicle formulation that combines amphotericin B (50 mg) with 350 mg of lipid (phosphatidylcholine, cholesterol, and distearoylphosphatidylglycerol, in molar ratio of 10 5 4) in an -10% molar ratio. Amphotericin B lipid complex (ABLC, abelcet) contains dimyristoylphosphatidylcholine and dimyristoylphosphatidylglycerol in a 7 3 mixture with -35 mol% of amphotericin B. 

Intrinsic proteins can also modify the order of phospholipid hydrocarbon chains. When cytochrome oxidase is reconstituted into vesicles of dimyristoylphosphatidylcholine, deuterated at the fatty acid methyl end, it is seen that Avq varies with the protein/ lipid ratios. Experiments performed with the lipid in the liquid-crystalline (fluid) state show (Fig. 9.24) that lipid order decreases as the protein concentration in the bilayer increases (Kang etal., 1979). This is attributed to the rough irregular protein surface in contact with the acyl chains. 

ATP inhibit nonspecific nucleotidases. Another way to prepare [a P] GTP Arfl for the GAP assay is to incubate Arfl with 25 ruM HEPES, pH 7.4, 100 mM NaCl, 3.5 mM MgCl2, 1 mM EDTA, 1 mM ATP, 1 fjM [a PJGTP (specific activity = 50,000-250,000 cpm/pmol), 25 ruM KCl, 1.25 U/ml pyruvate kinase, and 3 mM phosphoenolpyruvate. This buffer contains a GTP regenerating system. If using Arfl that has not been myristoy-lated, include 0.1% (w/v) Triton X-100. For myristoylated Arfl, use either micelles of 3 mM dimyristoylphosphatidylcholine and 0.1% cholate, pH 7.4 or use vesicles prepared by extrusion or sonication (see Chapter 15 of this volume. Assay and Properties of the Arf GAPs AGAPl, ASAPl, and ArfGAPl). 

Table 1 Rate constants for exit, k, and entrance, and exit rate constants for the surfactant monomer from SDS micelles, dimyristoylphosphatidylcholine (DMPC), and pyrene from DMPC vesicles.

In general, vesicles exhibit a phase transition behavior that is very different from that observed with multilamellar (liposomes or lamellar mesophase) preparations [90-93]. Suurkuusk et al. [92] found that unsonicated (multilamellar liposome) and sonicated (vesicle) samples of dimyristoylphosphatidylcholine exhibit different heat capacity maxima (Fig. 9) [94]. This difference implies a change in the organization of the phospholipids upon sonication. ESR and NMR spectroscopy showed that the small radius of curvature of the vesicles leads to less efficient packing and to greater freedom of motion of the hydrocarbon chains. The phase diagram of reversed vesicles was studied by DSC by Kunieda et al. [95],... 

FIG. 9 DSC thermograms of unsonicated multilamellar and sonicated vesicle suspensions prepared from dimyristoylphosphatidylcholine 0.1% w/v. (From Ref. 94.)... 

Laggner, P., Gotto, A.M., and Morisett, J.D., 1979, Structure of the dimyristoylphosphatidylcholine vesicle and the complex formed by its interaction with apolipoprotein C-III. X-ray small-angle scattering studies. Biochemistry, 18 164. 

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