Deuteron N.M.R. relaxation studies of phospholipid membranes

A unique model membrane system composed of a synthetic amphiphilic peptide (Lys2-Gly-Leu16-Lys2-Ala-amide) and a specifically labeled phospholipid (1,2-[7,7-2H2]dipalmitoyl-sn-glycero-3-phosphocholine) has been studied by 2H NMR, using inversion recovery, quadrupolar echo, and modified Jeener-Broekaert sequences, from 213 to 333 K, at molar peptide concentrations of 0, 2, 4, and 6%. Analysis of the experiments, employing a density matrix treatment based on the stochastic Liouville equation, revealed information about the dynamic organization of the lipid in the model membrane system, whose phase behavior has been determined previously [Huschilt et al. (1985) Biochemistry 24, 1377-1386]. The dynamic organization is described in terms of segmental and molecular order parameters and in terms of correlation times corresponding to both internal and overall lipid motions. In the liquid crystalline phase, the molecular order parameter, SZZ, was observed to decrease slightly upon addition of peptide while the conformational order parameter corresponding to the seventh segment, SZ'Z', did not change for any concentration of peptide. In general, the gauche-trans isomerization rate in the middle of the chain was not observed to change upon peptide addition, whereas the whole body reorientational correlation times (tau R parallel and tau R perpendicular) increased by nearly an order of magnitude. The anisotropy ratio (tau R perpendicular/tau R parallel) decreased with peptide added. An additional motion which involves a jump about the axis of the sn-2 chain is also observed to be slowed down significantly in the presence of peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

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“…Generally, the results for DPPC were found to be remarkably similar to those reported by Mayer et al (1988) for DMPC.…”

supporting

confidence: 87%

Deuterium NMR relaxation studies of peptide-lipid interactions

Prosser¹,

Davis²,

Mayer³

et al. 1992

Biochemistry

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“…EPR spectra are sensitive to motions with correlation times between 10 À10 and 10 À8 s [55], whereas 2 H NMR spectra are particularly sensitive to motions with correlation times between 10 À3 and 10 À9 s [56]. The orientational ordering that characterizes the rotation and wobbling motions of the stearic acid molecule will be in the fast-motion regime on the NMR time scale [29,57]. In addition, the deuterium-labels reveal the structure of the unperturbed bilayer, while the spinlabels detect the response of that segment of the bilayer attached to the doxyl group under a small physical stress due to the presence of the nitroxide moiety.…”

Section: Discussionmentioning

confidence: 99%

Investigating fatty acids inserted into magnetically aligned phospholipid bilayers using EPR and solid-state NMR spectroscopy

Nusair

Tiburu

Dave

et al. 2004

Journal of Magnetic Resonance

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“…The temperature dependence of these NMR experiments is an important parameter, because both the Boltzmann distribution of order parameters and the Arrhenius dependence of the relaxation rates may be revealed by the trends in relaxation times in these regimes [8]. A comprehensive set of temperature-dependent T 1 Z values has been reported for DMPC specifically deuterated at the C2, C6, C13, and C14 positions of the acyl chain [38]. Both inter-molecular segmental isomerization and the intra-molecular anisotropic mean-field ordering potential have been considered through fitting to multiple reorientational correlation times.…”

Section: Nmr Relaxation Gives Dynamical Parameters That Characterimentioning

confidence: 99%

An NMR database for simulations of membrane dynamics

Leftin

Brown

2011

Biochimica et Biophysica Acta (BBA) - Biomembranes

102

119

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Computational methods are powerful in capturing the results of experimental studies in terms of force fields that both explain and predict biological structures. Validation of molecular simulations requires comparison with experimental data to test and confirm computational predictions. Here we report a comprehensive database of NMR results for membrane phospholipids with interpretations intended to be accessible by non-NMR specialists. Experimental 13C–1H and 2H NMR segmental order parameters (SCH or SCD) and spin-lattice (Zeeman) relaxation times (T1Z) are summarized in convenient tabular form for various saturated, unsaturated, and biological membrane phospholipids. Segmental order parameters give direct information about bilayer structural properties, including the area per lipid and volumetric hydrocarbon thickness. In addition, relaxation rates provide complementary information about molecular dynamics. Particular attention is paid to the magnetic field dependence (frequency dispersion) of the NMR relaxation rates in terms of various simplified power laws. Model-free reduction of the T1Z studies in terms of a power-law formalism shows that the relaxation rates for saturated phosphatidylcholines follow a single frequency-dispersive trend within the MHz regime. We show how analytical models can guide the continued development of atomistic and coarse-grained force fields. Our interpretation suggests that lipid diffusion and collective order fluctuations are implicitly governed by the viscoelastic nature of the liquid-crystalline ensemble. Collective bilayer excitations are emergent over mesoscopic length scales that fall between the molecular and bilayer dimensions, and are important for lipid organization and lipid-protein interactions. Future conceptual advances and theoretical reductions will foster understanding of biomembrane structural dynamics through a synergy of NMR measurements and molecular simulations.

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Deuteron N.M.R. relaxation studies of phospholipid membranes

Cited by 63 publications

References 32 publications

Deuterium NMR relaxation studies of peptide-lipid interactions

Deuterium NMR relaxation studies of peptide-lipid interactions

Investigating fatty acids inserted into magnetically aligned phospholipid bilayers using EPR and solid-state NMR spectroscopy

An NMR database for simulations of membrane dynamics

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