A statistical mechanical treatment of fatty acyl chain order in phospholipid bilayers and correlation with experimental data. B. Dipalmitoyl-3-sn-phosphatidylcholine

Meraldi, Jean‐Paul; Schlitter, Jürgen

doi:10.1016/0005-2736(81)90190-5

Cited by 47 publications

(21 citation statements)

References 43 publications

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“…For the Lp phase ng--1.2 has been derived (Pink et al 1980). Theoretical predictions for n o in the L~ phase are: 4.0 (Meraldi and Schlitter 1981), 3.9 (Gruen 1981), and 3.1 (Marsh 1974). The L~ simulation compares well with theoretical predictions, but experimental values are somewhat higher.…”

Section: Hydrocarbon Chain Conformations and Flexibilitymentioning

confidence: 68%

“…The deviation in the C15 positions is substantial, but the experimental data for this position are not realistic as C14 and C15 positions differ by more than a bond length. In the theoretical model of Meraldi and Schlitter (1981), neutron diffraction data can be reproduced except for the Cls position, just as in our simulations. The agreement with Wiener and White (1992 a) is much better: these authors find a width of 0.5 nm for the terminal methyl.…”

Section: Charge Dandtributionsmentioning

confidence: 85%

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Molecular dynamics simulation of a phospholipid membrane

1994

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We present the results of molecular dynamics (MD) simulations of a phospholipid membrane in water, including full atomic detail. The goal of the simulations was twofold: first we wanted to set up a simulation system which is able to reproduce experimental results and can serve as a model membrane in future simulations. This goal being reached it is then further possible to gain insight in to those properties that are experimentally more difficult to access. The system studied is dipalmitoylphosphatidylcholine/water, consisting of 5408 atoms. Using original force field parameters the membrane turned out to approach a gel-like state. With slight changes of the parameters, the system adopted a liquid-crystalline state. Separate 80 ps runs were performed on both the gel and liquid-crystalline systems. Comparison of MD results with reliable experimental data (bilayer repeat distance, surface area per lipid, tail order parameters, atom distributions) showed that our simulations, especially the one in the liquid-crystalline phase, can serve as a realistic model for a phospholipid membrane. Further analysis of the trajectories revealed valuable information on various properties. In the liquid-crystalline phase, the interface turns out to be quite diffuse, with water molecules penetrating into the bilayer to the position of the carbonyl groups. The 10-90% width of the interface turns out to be 1.3 nm and the width of the hydrocarbon interior 3.0 nm. The headgroup dipoles are oriented at a small angle with respect to the bilayer plane. The resulting charge distribution is almost completely cancelled by the water molecules. The electron density distribution shows a large dip in the middle of the membrane. In this part the tails are more flexible. The mean life time between dihedral transitions is 20 ps. The average number of gauche angles per tail is 3.5. The occurrence of kinks is not a significant feature.

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Section: Hydrocarbon Chain Conformations and Flexibilitymentioning

confidence: 68%

Section: Charge Dandtributionsmentioning

confidence: 85%

Molecular dynamics simulation of a phospholipid membrane

1994

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“…FT-IR spectroscopy of specifically labeled DPPC yields a value of only 0.21 (Mendelsohn et al 1989). It should be noted, however, that the relative probabilities of the different conformers deduced from hard core repulsion theory by Meraldi and Schlitter (1981) depend on the conformation of the first segment of the acyl chains, on the chosen lateral pressure, and on the assumption that wobbling motions are absent, i.e. Sa= 1.…”

Section: (Ezqq') S Avq±i =-~[~)mentioning

confidence: 97%

Acyl chain conformational ordering in liquid-crystalline bilayers: comparative FT-IR and 2H-NMR studies of phospholipids differing in headgroup structure and chain length

1994

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FT-IR spectroscopy has been used to evaluate the acyl chain conformational ordering of DMPC, DMPE, DMPA (pH 6 and 12), DMPG (pH 1 and 7), and DPPC, DPPE, DPPA (pH 6). The frequencies of the symmetric and antisymmetric methylene stretching vibrations were determined as a function of temperature. In the liquid-crystalline phase the frequencies show a qualitative dependence on the amount of chain disorder. Quantitative data for trans-gauche isomerization were obtained from the integral intensities of the conformation sensitive methylene wagging absorptions at ca. 1368 cm -j (gtg' and gtg sequences), 1356 cm 1 (double gauche) and 1342 cm -1 (end gauche). The integral band intensities were converted to the number of gauche conformers per acyl chain using the calibration factors published by Senak et al. (1991). At 69 °C the highest number of gauche conformers excluding contributions from single gauche conformers and jogs (g'tttg) are found for PCs (DMPC: 2.6; DPPC: 2.4), followed by DMPG-(2.0), phosphatidylethanolamines (DMPE: 1.4; DPPE: 2.0), protonated DMPG (1.5), and phosphatidic acids (DPPA-: 1.7; DMPA-: 1.4, DMPA2-: 1.7). From 2H-NMR measurements of perdeuterated samples of DMPC, DMPA, DPPC, and DPPA the quadrupolar splittings AVQ± i and the order parameter ScD i of the CDz-segments close to the chain ends could be determined whereas splittings in the plateau region of the chains could not be resolved. The quadrupolar splittings are affected by trans-gauche isomerization, long axis rotation, and reAbbreviations: FT-IR, Fourier transform infrared, 2H-NMR, deuterium nuclear magnetic resonance; DMPC(-d54), (perdeuterated) dimyristoyl-phosphatidylcholine; DMPE(-d54 ), (perdeuterated) dimyristoyl-phosphatidylethanolamine; DMPA (-d54), (perdeuterated) dimyristoyl-phosphatidie acid; DMPG, dimyristoyl-phosphatidylglycerol; DPPC(-d62),, (perdeuterated) dipalmitoyl-phosphatidylcholine; DPPE(-d62), (perdeuterated) dipalmitoyl-pbosphatidylethanolamine; DPPA(-d62), (perdeuterated) dipalmitoyl-phosphatidic acid; gtg, gauche-+-trans-gauche*; gtg', gauche-+-trans-gauche*; dg, double gauche; eg, end gauche Correspondence to: A. Blume stricted wobbling motions of the acyl chains. In the simplest assumption, the order parameter ScD can be expressed as a product of a segmental order parameter S 7 and a chain order parameter S a. For comparison of the different lipids we used average order parameters ScD, obtained by averaging over all ScDi-values, and $7 determined from the total number of gauche conformers per chain by FT-IR-spectroscopy, to calculate an empirical average chain order parameter Sc~-. The combination of 2H-NMR and FT-IR results allows the estimation of the relative extent of chain wobbling for the different lipid molecules. Sa is lowest for PCs (Sa =0.475) while PEs (Sa =0.51) and PAs (Sa =0.52) show less chain wobbling.

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“…The first class contains all the microscopic models which are differentiated by the extent to which the various lipid hydrocarbon chain states are taken into account. These are (i) those that include all conformational states (29)(30)(31)(32)(33)(34)(35)(36), (ii) those that include the "important" conformational states (37,38), (iii) those that consider two conformational states (39)(40)(41), and (iv) others (42)(43)(44)(45)(46). The second class consists of phenomenological models such as those which make use of Landau-Ginzburg theory (47)(48)(49)(50) and have been discussed elsewhere (12).…”

Section: Models Of the Statics And Dynamics Of Lipid Hydrocarbon Chaimentioning

confidence: 99%

Theoretical studies of phospholipid bilayers and monolayers. Perturbing probes, monolayer phase transitions, and computer simulations of lipid–protein bilayers

Pink¹

1984

Can. J. Biochem. Cell Biol.

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This paper describes some mathematical models for studying properties of lipid bilayer membranes. It is shown that there is evidence from fluorescent probe and electron spin resonance studies that some integral proteins are "randomly" distributed in the plane of a lipid bilayer for T greater than Tc, so that protein-protein "contacts" can occur. This implies that there is no permanent annulus of lipids around these proteins, so that there is no unique stoichiometric ratio of "boundary lipids" to protein. Computer simulation techniques are reviewed and comments are made about some recently introduced methods. Dynamical models of lipid--integral protein bilayers are outlined and it is shown that much differential scanning calorimetry, freeze-fracture, X-ray, and 2H nuclear magnetic resonance data can be understood. It is predicted that specific heat curves should show a rise at a temperature, TK less than Tc, at which a protein-rich phase starts to "melt"; that dipalmitoyl phosphatidylcholine (DPPC) hydrocarbon chains in such a protein-rich phase should exhibit some static disorder down to approximately -10 degrees C, around which they should freeze noncooperatively; and that the crossing of phase boundaries, as protein concentration expressed as mole fraction X changes just below Tc, should be reflected in a complicated dependence of protein lateral motion upon X. Models to study the liquid condensed-liquid expanded (LC-LE) transition of phosphatidylcholine (PC) monolayers at the air-water interface are described. The rounding in the LC phase of pressure-area isotherms are understood as the melting of microscopic gel-phase "domains" into macroscopic regions of fluid-phase lipids. There is some experimental support for this. Finally, to model the difference between a monolayer and the corresponding bilayer, an interaction is introduced between the two halves of a bilayer. It is shown to be very weak in the case of PC bilayers and it is outlined in the paper how monolayer and bilayer thermodynamics can be related. It was found that the internal lateral pressure of a DPPC bilayer is approximately 30 dyn/cm (1 dyn = 10 microN).

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A statistical mechanical treatment of fatty acyl chain order in phospholipid bilayers and correlation with experimental data. B. Dipalmitoyl-3-sn-phosphatidylcholine

Cited by 47 publications

References 43 publications

Molecular dynamics simulation of a phospholipid membrane

Molecular dynamics simulation of a phospholipid membrane

Acyl chain conformational ordering in liquid-crystalline bilayers: comparative FT-IR and 2H-NMR studies of phospholipids differing in headgroup structure and chain length

Theoretical studies of phospholipid bilayers and monolayers. Perturbing probes, monolayer phase transitions, and computer simulations of lipid–protein bilayers

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