Dimyristoylphosphatidylcholine bilayer

Widomska, J. and W.K. Subczynski. 2008. Transmembrane localization of cis-isomers of zeaxanthin in the host dimyristoylphosphatidylcholine bilayer membrane. Biochim. Biophys. Acta 1778 10-19. 

Figure 5. (a) Profile of the hydrophobic barrier in a phosphatidylcholine liposome. The circles are measured points based upon the polarity index [54] the solid line is the dielectric constant as determined with fluorescent probes [55]. (b) Calculated relative free energy for diffusion of CH across a dimyristoylphosphatidylcholine bilayer (adapted from [57h]). In both diagrams, distances are measured from the center of the bilayer. 

Hogberg CJ, Lyubartsev AP (2006) A molecular dynamics investigation of the influence of hydration and temperature on structural and dynamical properties of a dimyristoylphosphatidylcholine bilayer. J Phys Chem B 110 14326... 

Fig. 1 Potential of mean force (relative free energy) for methane across a lipid (dimyristoylphosphatidylcholine) bilayer.The areas corresponding to the regions of the hilayer are labeled.The lower curve shows the probabiUty distribution of the atoms in the PC headgroups...

Some fairly typical results, obtained by LaMer and co-workers [275] are shown in Fig. IV-24. At the higher film pressures, the reduction in evaporation rate may be 60-90%—a very substantial effect. Similar results have been reported for the various fatty acids and their esters [276,277]. Films of biological materials may offer little resistance, as is the case for cholesterol [278] and dimyristoylphosphatidylcholine (except if present as a bilayer) [279]. 

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. 

In contrast to (VIII), biradical (VII) shows a strong concentration, cholesterol- and temperature-dependent spin-spin interaction. Rey and McConnell41 have analyzed these spectra quantitatively when the concentration of (VII) is varied between 0.025 mole % and 2 mole % in bilayer membranes (70 mole % dimyristoylphosphatidylcholine and 30 mole % cholesterol) at 30°C. The surprising result was obtained that all the spectra can be accounted for quantitatively as the superposition of two spectra, a monomer spectrum [one molecule of (VII)] and a hexamer spectrum [a cluster containing six molecules of (VII)]. Representative data are given in Figs. 8 and 9. 

Fig. 36. Electron micrograph of ripple structure and patch formation in 1 1 mixed bilayers of (18, n = 12) and dimyristoylphosphatidylcholine. Bar represents 250 nm...

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... 

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... 

Sanders CR, Schwonek JP (1992) Characterization of magnetically orientable bilayers in miKtures of dihexanoylphosphatidylcholine and dimyristoylphosphatidylcholine by solid-state NMR. Biochemistry 31 8898-8905... 

It is anticipated that oligomerization as well as lattice formation is not always straightforward for a number of membrane proteins overexpressed in a host cell like E. coli, unless identiflcation and incorporation of such specific endogenous lipids to promote the formation of a 2D lattice are seriously taken into account. As a reference system to examine the NMR spectra of such proteins by site-directed NMR approach, it seems to be very important to gain an insight into how the NMR spectra of [3- C]Ala- or [l- C]Val-labeled bR incorporated into neutral lipid bilayers such as egg phosphatidylcholine (PQ, dimyristoylphosphatidylcholine (DMPC) or dipalmytoylphosphatidylcholine (DPPC) are modified by the presence or absence of a 2D crystalline lattice. 

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. 

This method was initially tested with water simulations where FM was done with reference force from ab-initio CP-MD calculations. Further this method was applied to liquid state systems by matching the force from classical all atomistic MD to CG MD. The same method was also tested for biomolecules such as dimyristoylphosphatidylcholine (DMPC) lipid bilayer and ionic liquids. 

---