Generalized Model-Free Analysis of Nuclear Spin Relaxation Experiments

Xu, Xiaolin; Struts, Andrey V.; Brown, Michael F.

doi:10.1002/9780470034590.emrstm1367

Cited by 15 publications

(26 citation statements)

References 20 publications

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“…The various motions are described by their mean-squared amplitudes and (reduced) spectral densities, and they may include cross correlations due to their statistical (in) dependence (66)(67)(68). The segmental order parameters (S CH or S CD ) describe the composite motion in terms of the residual couplings (dipolar or quadrupolar) as compared to the static values (43).…”

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

108

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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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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

108

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“…2 presents examples of solid-state 2 H NMR spectra obtained for randomly oriented samples of rhodopsin with specifically 2 H-labeled methyl groups of retinal at the C5, C9, or C13 carbon positions. An important aspect is that experimental information about the molecular dynamics is uniquely available from such solid-state 2 H NMR studies (11). Moreover, certain information on the orientational distribution of the labeled molecular groups (distribution versus the average orientation) can be derived from the spectral line shape, as described below.…”

Section: Methodsmentioning

confidence: 99%

“…The spectral densities depend on the orientation of the methyl group in the sample with respect to the magnetic field, together with the mean-square amplitudes and rates of the motions. Analysis of the NMR relaxation times in terms of molecular motions can be performed using our generalized model-free approach (11), which provides the spectral densities J m (ω) for time-dependent rotational transformations connecting components of quadrupolar tensor in the molecular and laboratory frames. As an alternative, specific motional models can be introduced (10).…”

Section: Methodsmentioning

confidence: 99%

“…Site-directed 2 H NMR spectroscopy provides orientational constraints for functional molecular groups, and relaxation times characterize their thermal fluctuations. The results can be further analyzed using a generalized model-free approach (9–11) to obtain novel information about the molecular dynamics (see below). Structural and dynamical modeling allows one to determine both the local conformation and correlation times of the molecular motions at an atomistically resolved level (9–11).…”

Section: Introductionmentioning

confidence: 99%

“…The results can be further analyzed using a generalized model-free approach (9–11) to obtain novel information about the molecular dynamics (see below). Structural and dynamical modeling allows one to determine both the local conformation and correlation times of the molecular motions at an atomistically resolved level (9–11). In this article we outline the methodology for solid-state 2 H NMR studies of the retinal cofactor bound to rhodopsin, including trapping of rhodopsin photointermediates in aligned membrane films.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Investigation of Rhodopsin Dynamics in Its Signaling State by Solid-State Deuterium NMR Spectroscopy

Struts

Chawla

Perera

et al. 2015

Methods in Molecular Biology

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Site-directed deuterium NMR spectroscopy is a valuable tool to study the structural dynamics of biomolecules in cases where solution NMR is inapplicable. Solid-state 2H NMR spectral studies of aligned membrane samples of rhodopsin with selectively labeled retinal provide information on structural changes of the chromophore in different protein states. In addition, solid-state 2H NMR relaxation time measurements allow one to study the dynamics of the ligand during the transition from the inactive to the active state. Here we describe the methodological aspects of solid-state 2H NMR spectroscopy for functional studies of rhodopsin, with an emphasis on the dynamics of the retinal cofactor. We provide complete protocols for the preparation of NMR samples of rhodopsin with 11-cis-retinal selectively deuterated at the methyl groups in aligned membranes. In addition, we review optimized conditions for trapping the rhodopsin photointermediates; and lastly we address the challenging problem of trapping the signaling state of rhodopsin in aligned membrane films.

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Cholesterol Effects on the Physical Properties of Lipid Membranes Viewed by Solid-state NMR Spectroscopy

Molugu

Brown

2019

Advances in Experimental Medicine and Biology

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Generalized Model-Free Analysis of Nuclear Spin Relaxation Experiments

Cited by 15 publications

References 20 publications

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

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

Investigation of Rhodopsin Dynamics in Its Signaling State by Solid-State Deuterium NMR Spectroscopy

Cholesterol Effects on the Physical Properties of Lipid Membranes Viewed by Solid-state NMR Spectroscopy

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