Analysis of Simulated NMR Order Parameters for Lipid Bilayer Structure Determination

Petrache, Horia I.; Tu, Kechuan; Nagle, John F.

doi:10.1016/s0006-3495(99)77403-5

Cited by 103 publications

(145 citation statements)

References 19 publications

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“…The new method gives nearly identical numerical results as the method employed earlier for DPPC by Brown's group [8] that gave A = 71.7Å 2 . When applied to DMPC data [18], it gives A = 65.4Å 2 [27]. Both these values are considerably higher than the values given by the EDP method and even higher than the GXC values, which should provide an upper bound.…”

Section: Comparison With Some Other Resultsmentioning

confidence: 99%

“…This range is due, not to different primary data for the S CD order parameters, but from different methods of interpretating those data to give A. A recent attempt to improve the interpretation employed simulations and a method emerged that fit the simulations very well [27]. The new method gives nearly identical numerical results as the method employed earlier for DPPC by Brown's group [8] that gave A = 71.7Å 2 .…”

Section: Comparison With Some Other Resultsmentioning

confidence: 99%

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Lipid bilayer structure

Nagle

Tristram-Nagle

2000

Current Opinion in Structural Biology

186

200

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Section: Comparison With Some Other Resultsmentioning

confidence: 99%

Section: Comparison With Some Other Resultsmentioning

confidence: 99%

Lipid bilayer structure

Nagle

Tristram-Nagle

2000

Current Opinion in Structural Biology

186

200

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“…Namely, higher ordering of the lipid tails has been shown to lead to a smaller area per lipid. 14,70 Hence, the cholesterol-rich areas should also have a smaller area per lipid in atomistic simulations, if we could observe them.…”

Section: B Organization Of Cholesterolmentioning

confidence: 98%

Coarse-grained model for phospholipid/cholesterol bilayer employing inverse Monte Carlo with thermodynamic constraints

Murtola¹,

Falck²,

Karttunen³

et al. 2007

The Journal of Chemical Physics

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The authors introduce a coarse-grained (CG) model for a lipid membrane comprised of phospholipids and cholesterol at different molar concentrations, which allows them to study systems that are approximately 100nm in linear size. The systems are studied in the fluid phase above the main transition temperature. The effective interactions for the CG model are extracted from atomic-scale molecular dynamics simulations using the inverse Monte Carlo (IMC) technique, an approach similar to the one the authors used earlier to construct another CG bilayer model [T. Murtola et al., J. Chem. Phys. 121, 9156 (2004)]. Here, the authors improve their original CG model by employing a more accurate description of the molecular structure for the phospholipid molecules. Further, they include a thermodynamic constraint in the IMC procedure to yield area compressibilities in line with experimental data. The more realistic description of the molecular structure of phospholipids and a more accurate representation of the interaction between cholesterols and phospholipid tails are shown to improve the behavior of the model significantly. In particular, the new model predicts the formation of denser transient regions in a pure phospholipid system, a finding that the authors have verified through large scale atomistic simulations. They also find that the model predicts the formation of cholesterol-rich and cholesterol-poor domains at intermediate cholesterol concentrations, in agreement with the original model and the experimental phase diagram. However, the domains observed here are much more distinct compared to the previous model. Finally, the authors also explore the limitations of the model, discussing its advantages and disadvantages.

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“…That model assumes discrete orientations of acyl chain segments as the most probable conformations. Although initially it appeared to be in reasonably good agreement with scattering experiments, discrepancies between the area calculations from more accurate 2 H NMR and x-ray scattering measurements became evident (73,74). The mean-torque model was proposed as an alternative (35), as it assumes a continuum distribution for the orientations of acyl chain segments.…”

Section: Theoretical Framework Of Mean-torque Modelmentioning

confidence: 99%

Area per Lipid and Cholesterol Interactions in Membranes from Separated Local-Field 13 C NMR Spectroscopy

Leftin

Molugu

Job

et al. 2014

Biophysical Journal

111

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Investigations of lipid membranes using NMR spectroscopy generally require isotopic labeling, often precluding structural studies of complex lipid systems. Solid-state (13)C magic-angle spinning NMR spectroscopy at natural isotopic abundance gives site-specific structural information that can aid in the characterization of complex biomembranes. Using the separated local-field experiment DROSS, we resolved (13)C-(1)H residual dipolar couplings that were interpreted with a statistical mean-torque model. Liquid-disordered and liquid-ordered phases were characterized according to membrane thickness and average cross-sectional area per lipid. Knowledge of such structural parameters is vital for molecular dynamics simulations, and provides information about the balance of forces in membrane lipid bilayers. Experiments were conducted with both phosphatidylcholine (dimyristoylphosphatidylcholine (DMPC) and palmitoyloleoylphosphatidylcholine (POPC)) and egg-yolk sphingomyelin (EYSM) lipids, and allowed us to extract segmental order parameters from the (13)C-(1)H residual dipolar couplings. Order parameters were used to calculate membrane structural quantities, including the area per lipid and bilayer thickness. Relative to POPC, EYSM is more ordered in the ld phase and experiences less structural perturbation upon adding 50% cholesterol to form the lo phase. The loss of configurational entropy is smaller for EYSM than for POPC, thus favoring its interaction with cholesterol in raftlike lipid systems. Our studies show that solid-state (13)C NMR spectroscopy is applicable to investigations of complex lipids and makes it possible to obtain structural parameters for biomembrane systems where isotope labeling may be prohibitive.

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Analysis of Simulated NMR Order Parameters for Lipid Bilayer Structure Determination

Cited by 103 publications

References 19 publications

Lipid bilayer structure

Lipid bilayer structure

Coarse-grained model for phospholipid/cholesterol bilayer employing inverse Monte Carlo with thermodynamic constraints

Area per Lipid and Cholesterol Interactions in Membranes from Separated Local-Field 13 C NMR Spectroscopy

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