Phosphatidylcholine bilayers

A selection of the predictions of the equilibrium structure of DPPC bilayers as found by numerical self-consistent-field calculations is given in the following figures. In a series of articles, the SCF predictions for such membranes were published, starting in the late 1980s. As discussed above, we will update these early predictions for the theory outlined above with updated parameter sets. The calculations are very inexpensive with respect to the CPU time, and thus variations of the parameter-set will also provide deeper insight into the various subtle balances that eventually determine the bilayer structure - the mechanical properties as well as the thermodynamic properties. 

The free volume density in water is fixed to the equilibrium value found for the water-vapour coexistence calculations pJ = 0.042575. This value was fixed, which implies, from a lattice-gas perspective, that the pressure was fixed to some reference value, i.e. p = 1. 

Together with the known positions of the chain segments and the order along the chain, we can deduce that the central region in the bilayer is slightly more disordered than the outer part of the core. Such a result is relevant for the mechanism of incorporation of foreign objects in the bilayer. 

The two chains in the lipid bilayer are not identical, because they are positioned asymmetrically with respect to the PC head. It turns out that the tail closest to the head group is buried less deep in the bilayer than the other chain [98]. The difference is not very large it amounts to about half a segment size. From this difference, we can rationalise the disparities in order between the two tails. The chain that is pulled out will be stretched most, and the order tends to be higher than the other chain. Below we will see that the differences in the behaviour of the tails can become larger if there are differences between the tails, e.g. with respect to the degree of unsaturation. 

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We finish this section by comparing our results with NMR and incoherent neutron scattering experiments on water dynamics. Self-diffusion constants on the millisecond time scale have been measured by NMR with the pulsed field gradient spin echo (PFGSE) method. Applying this technique to oriented egg phosphatidylcholine bilayers, Wassail [68] demonstrated that the water motion was highly anisotropic, with diffusion in the plane of the bilayers hundreds of times greater than out of the plane. The anisotropy of... 

Thomas, P. G. Seelig, J., Binding of the calcium antagonist flunarizine to phosphatidylcholine bilayers Charge effects and thermodynamics, Biochem. J. 291, 3974-02 (1993). 

Chaturvedi, V.K. and C.K.R. Kurup. 1986. Interaction of lutein with phosphatidylcholine bilayers. Biochim. Biophys. Acta 860 286-292. 

Jemiola-Rzeminska M, Pasenkiewicz-Gierula M, and Strzatka K. 2005. The behaviour of beta-carotene in the phosphatidylcholine bilayer as revealed by a molecular simulation study. Chemistry and Physics of Lipids 135(1) 27-37. 

Clarke RJ (1997) Effect of lipid structure on the dipole potential of phosphatidylcholine bilayers. Biochim Biophys Acta-Biomembr 1327(2) 269-278... 

Shibata, A., Ikawa, K. and Terada, H. (1995). Site of action of the local anaesthetic tetracaine in a phosphatidylcholine bilayer with incorporated cardiolipin, Biophys. J., 69, 470-477. 

Hresko R. C., Sugar I. P., Barenhoiz Y. and Thompson T. E. (1986) Lateral Diffusion of a Pyrene-Labeled Phosphatidylcholine in Phosphatidylcholine Bilayers/Fluorescence Phase and Modulation Study, Biochemistry 25, 3813-3823. 

V. B. Yashar, M. Menashe, R. L. Biltonen, M. L. Johnson, and Y. Barenholz, Interaction of frans-parinaric acid with phosphatidylcholine bilayers Comparison with the effect of other fluorophores, Biochim. Biophys. Acta 904, 117-124 (1987). 

E. Friere, T. Markello, C. Rigell, and P. W. Holloway, Calorimetric and fluorescence characterization of interactions between cytochrome bs and phosphatidylcholine bilayers, Biochemistry 22, 1675-1680 (1983). 

J. R. Lakowicz, D. Hogen, and G. Omann, Diffusion and partitioning of a pesticide, lindane, into phosphatidylcholine bilayers, Biochim. Biophys. Acta 471, 401—411 (1977). 

It is interesting that modifying solution conditions by adding different concentrations of ethanol can produce a biphasic effect on melting transition temperatures of lipid-like systems (e.g., acyl chains of hydrocarbons). For example, low concentrations of ethanol reduce the Tm of phosphatidylcholine bilayers, whereas higher concentrations increase the Tm of the same system.122 This effect has been shown to depend upon acyl chain length and can be explained by the... 

For pure phosphatidylcholine bilayers, the orientation of the headgroup has been well characterized showing that headgroups are aligned approximately parallel to the bilayer surface. Because only one phosphorus with 100% natural abundance is contained in the phospholipid molecule, NMR has become an important tool to study the phospholipid headgroup structure and dynamics. ... 

Pitman, M.C., Suits, F., Mackerell, A.D. Jr., Feller, S.E. Molecular-level organization of saturated and polyunsaturated fatty acids in a phosphatidylcholine bilayer containing cholesterol. Biochem. 2004, 43, 15318-28. 

AA Omran, K Kitamura, S Takegami, A-AY El-Sayed, M Abdel-Mottaleb. Determination of partition coefficients of diazepam and flurazepam between phosphatidylcholine bilayer vesicles and water by second derivative spectro-photometric method. J Pharm Biomed Anal 25 319-324, 2001. 

Limbacher HP Jr., Blickenstaff GD, Bowen JH, et al. Multiequilibrium binding of a spin-labeled local anesthetic in phosphatidylcholine bilayers. Biochim Biophys Acta 1985 812(l) 268-276. 

Experimental partitioning energies for various solutes between water and phosphatidylcholine bilayer were also well reproduced within the experimental error. 

The conventional model developed to explain cell membrane characteristics influencing drug permeability is routinely referred to as the fluid-mosaic model (Figures 2.1 and 2.2). In this model the main components, for our purposes, are a phospholipid (e.g., sphingomyelin and phosphatidylcholine) bilayer (8 nm), with polar moieties at both the external and internal surfaces, and with proteins periodically traversing the phospholipid plane perpendicularly. 

For measurements between crossed mica cylinders coated with phospholipid bilayers in water, see J. Marra andj. Israelachvili, "Direct measurements of forces between phosphatidylcholine and phosphatidylethanolamine bilayers in aqueous electrolyte solutions," Biochemistry, 24, 4608-18 (1985). Interpretation in terms of expressions for layered structures and the connection to direct measurements between bilayers in water is given in V. A. Parsegian, "Reconciliation of van der Waals force measurements between phosphatidylcholine bilayers in water and between bilayer-coated mica surfaces," Langmuir, 9, 3625-8 (1993). The bilayer-bilayer interactions are reported in E. A. Evans and M. Metcalfe, "Free energy potential for aggregation of giant, neutral lipid bilayer vesicles by van der Waals attraction," Biophys. J., 46, 423-6 (1984). 

V. A. Parsegian, "Reconciliation of van der Waals force measurements between phosphatidylcholine bilayer in water and between bilayer-coated mica surfaces," Langmuir, 9, 3625-8 (1993). 

Affinities of lanthanide ions for phosphatidylcholine bilayer membranes. 

Figure 9 shows force laws for phosphatidylcholine bilayers (Lis et al, 1982), determined by the osmotic stress method. Similar data were obtained for DNA samples (Rau et al., 1984). The characteristic length governing decay of the force is about 3 A for both systems. Interactions of this kind can also be important for protein aggregates. Prouty et al. (1985) used the osmotic stress method to determine the phase diagram of sickle cell hemoglobin (Fig. 10). At a critical osmotic pressure, which is temperature dependent, a solution of deoxyhemoglobin S collapses to a gel, with a large change in volume. One of the strengths of the osmotic stress method is that it provides additional information that can be used for thermodynamic analysis of the system.

Stockton, G. W. and Smith, I. C. P. (1976). A deuterium NMR smdy of the condensing effect of cholesterol on egg phosphatidylcholine bilayer membranes. 1. Per-deuterated fatty acid probes. Chem. Phys. Lipids 77 251. 

Chen SC, Sturtevant JM, Gaffney BJ. Scanning calorimetric evidence of a third phase transition in phosphatidylcholine bilayers. 40. Proc. Natl. Acad. Sci. U.S.A. 1980 77 5060-5064. 

Bultmann T, Vaz WLC, Melo ECC, Sisk RB, Thompson TE. Eluid-phase connectivity and translational diffusion in a eutectic 49. two-component, two-phase phosphatidylcholine bilayer. Biochemistry 1991 30 5573-5579. 

Second-derivative electronic absorption spectrophotometry, which is a method applied without any separation procedure, was used to determine the partition coefficients of three N-monodemethylated phenothiazine drugs, such as CPZ, triflupromazine and promazine, between the phosphatidylcholine bilayers of small unilamellar vesicles (SUVs) and water, in order to evaluate their affinity to biomembranes. The second-derivative spectra exhibited distinct isobestic points, confirming the entire elimination of the residual background signal effects of the SUVs which were observed in the conventional absorption spectra [161]. 

Physical Methods. H.p.l.c. procedures for the separation and assay of ubiquinone and homologues278-280 and of menaquinone cis- and fra/ts-isomers, 2,3-epoxides, and chain-length homologues281 282 have been described. A XH n.m.r. study has been reported283 of the location and motion of ubiquinones in perdeuteriated phosphatidylcholine bilayers. Other aspects of the interaction of ubiquinone with phospholipid monolayers have been studied.284... 

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