Multi‐dimensional pulsed field gradient magic angle spinning NMR experiments on membranes

Gaede, Holly C.; Gawrisch, Klaus

doi:10.1002/mrc.1329

Cited by 48 publications

(33 citation statements)

References 34 publications

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“…The laboratories of Stark and Epand confirmed that crosspeaks between water and lipid headgroups have negative intensity, but the crosspeak to the methylene resonance of hydrocarbon chains was weak and positive (Zhou et al 1999). More recently we confirmed the latter observation in an experiment with coherence selection by pulsed magnetic field gradients (PFG) (Gaede and Gawrisch 2004).…”

Section: Introductionsupporting

confidence: 67%

Hydration of POPC bilayers studied by 1H-PFG-MAS-NOESY and neutron diffraction

et al. 2007

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The stability of lipid bilayers is ultimately linked to the hydrophobic effect and the properties of water of hydration. Magic angle spinning (MAS) nuclear Overhauser enhancement spectroscopy (NOESY) with application of pulsed magnetic field gradients (PFG) was used to study the interaction of water with 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers in the fluid phase. NOESY cross-relaxation between water and polar groups of lipids, but also with methylene resonances of hydrophobic hydrocarbon chains, has been observed previously. This observation led to speculations that substantial amounts of water may reside in the hydrophobic core of bilayers. Here, the results of a quantitative analysis of cross-relaxation in a POPC/water mixture are reported. Coherences were selected via application of pulsed magnetic field gradients. This technique shortens acquisition times of NOESY spectra to 20 minutes and reduces t 1 -spectral noise, enabling detection of weak crosspeaks, like those between water and lipids, with higher precision than with non-gradient NOESY methods. The analysis showed that water molecules interact almost exclusively with sites of the lipid-water interface, including choline-, phosphate-, glycerol-, and carbonyl groups. The lifetime of lipid-water associations is rather short, on the order of 100 ps, at least one order of magnitude shorter than the lifetime of lipid-lipid associations. The distribution of water molecules over the lipid bilayer was measured at identical water content by neutron diffraction. Water molecules penetrate deep into the interfacial region of bilayers but water concentration in the hydrophobic core is below the detection limit of one water molecule per lipid, in excellent agreement with the cross-relaxation data.

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Section: Introductionsupporting

confidence: 67%

Hydration of POPC bilayers studied by 1H-PFG-MAS-NOESY and neutron diffraction

et al. 2007

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“…This quantity is analogous to the attractive component of the Lennard-Jones potential and is related to the rate of magnetization transfer measured in recent NMR experiments (49). All atoms of both molecules were used.…”

Section: Methodsmentioning

confidence: 99%

A role for direct interactions in the modulation of rhodopsin by ω-3 polyunsaturated lipids

Grossfield

Feller

Pitman

2006

Proc. Natl. Acad. Sci. U.S.A.

282

250

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Rhodopsin, the G protein-coupled receptor primarily responsible for sensing light, is found in an environment rich in polyunsaturated lipid chains and cholesterol. Biophysical experiments have shown that lipid unsaturation and cholesterol both have significant effects on rhodopsin's stability and function; -3 polyunsaturated chains, such as docosahexaenoic acid (DHA), destabilize rhodopsin and enhance the kinetics of the photocycle, whereas cholesterol has the opposite effect. Here, we use molecular dynamics simulations to investigate the possibility that polyunsaturated chains modulate rhodopsin stability and kinetics via specific direct interactions. By analyzing the results of 26 independent 100-ns simulations of dark-adapted rhodopsin, we found that DHA routinely forms tight associations with the protein in a small number of specific locations qualitatively different from the nonspecific interactions made by saturated chains and cholesterol. Furthermore, the presence of tightly packed DHA molecules tends to weaken the interhelical packing. These results are consistent with recent NMR work, which proposes that rhodopsin binds DHA, and they suggest a molecular rationale for DHA's effects on rhodopsin stability and kinetics.cholesterol ͉ molecular dynamics ͉ fatty acid ͉ protein-lipid interactions R hodopsin, the primary light receptor in the visual system, is an integral membrane protein belonging to the G proteincoupled receptor (GPCR) superfamily. GPCRs, the largest known protein superfamily, are critically important in a wide variety of biological signaling processes (1). As a result, half of all current drug targets belong to this family (2). Moreover, rhodopsin is the only GPCR whose structure is known to atomic resolution (3-7), making it important both in its own right and as a template for understanding GPCR function in general (1,8).Rhodopsin is found in the rod outer-disk membranes in the photoreceptor cells of vertebrates and invertebrates (9). These membranes are highly enriched in -3 polyunsaturated fatty acids (10, 11); the cholesterol content is very high in newly formed disk membranes and drops as they mature (12). The presence of lipids with polyunsaturated chains destabilizes the native state of rhodopsin and speeds the kinetics of the photocycle (13, 14), whereas cholesterol stabilizes rhodopsin and slows its kinetics (13-15). Although these experiments deepen our understanding, the molecular-level details of how the membrane environment modulates rhodopsin's structure and function are unknown.Molecular dynamics simulations can be a powerful tool to advance our understanding of protein-lipid biophysics. In recent years, a number of groups have published simulations of rhodopsin in monounsaturated (16-19) and polyunsaturated membranes (20, 21). Recent work from our group focused on the interactions between polyunsaturated lipids, cholesterol, and rhodopsin (20). In that work, we observed two docosahexaenoic acid (DHA) chains forming contacts deep in the protein interior, suggesting that DHA's...

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“…[92][93][94] Due to the anisotropic molecular reorientation of these liquid crystalline (LC) systems, significant dipolar coupling remains, leading to broad lines and short relaxation times. However dipolar coupling can be reduced through the use of MAS.…”

Section: Diffusion In Zeolites Nanoparticles and Liquid Crystalsmentioning

confidence: 99%