Rotating-frame relaxation studies of slow motions in fluorinated phospholipid model membranes

Peng, Zhengyu; Simplăceanu, Virgil; Lowe, I. J.; Ho, Chien

doi:10.1016/s0006-3495(88)82933-3

Cited by 28 publications

(17 citation statements)

References 33 publications

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“…Aside from those studies emphasizing lateral diffusion (9, 19), most existing models of the dynamics of phospholipids belong to one of two classes: (i) one or more noncollective anisotropic rotations of a lipid molecule (or a segment of the molecule) with well-defined correlation times (6-8, 10, 11, 16-18, 22); or (ii) collective bilayer disturbances with small angular modulations and a broad distribution of correlation times (13)(14)(15)20). Multiple motions coexist in a bilayer, even though different motions may have quite different geometries and time scales (20,21).Since most biochemical and biophysical processes occur on a microsecond or slower time scale, we believe that the slow motions of phospholipids (i.e., correlation time, r 2 10-6 sec) are more relevant to the function of biological membranes than their fast motions. Several studies have suggested that slow motions play an important role in lipidprotein interactions or lipid-mediated protein-protein interactions (4, 7, 14, 23).…”

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“…A number of nuclear magnetic resonance (NMR) investigations have focused on the molecular motions of phospholipids in a pure lipid bilayer, and various theoretical models have been proposed (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). Aside from those studies emphasizing lateral diffusion (9,19), most existing models of the dynamics of phospholipids belong to one of two classes: (i) one or more noncollective anisotropic rotations of a lipid molecule (or a segment of the molecule) with well-defined correlation times (6-8, 10, 11, 16-18, 22); or (ii) collective bilayer disturbances with small angular modulations and a broad distribution of correlation times (13)(14)(15)20).…”

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confidence: 99%

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“…Using macroscopically oriented bilayers prepared from a phospholipid with perdeuterated acyl chains in which a single CF2 group occurs at the 7 position of the sn-2 acyl chain, 1-(myristoyl-d27)-2-(7,7-difluoromyristoyl-d25)-sn-glycero-3-phosphocholine (2-[7,7-19F2]DMPC-d52), we have investigated both slow and fast motions by measuring 19F Tjp and 771 as a function of the bilayer orientation, the locking field, and the temperature. The advantages of using a '9F label include the following: the NMR sensitivity is high and there is no natural background (37); the relaxation of '9F is dominated by intramolecular interactions (21); and the crosspolarization between '9F and 2H is negligible in the range of locking fields employed in this study. We have found that adding cholesterol to bilayers of the perdeuterated fluorolipid can dramatically alter the orientation dependence of Tj7l, indicating that, besides increasing the intensity of the slow motions, a large perturbation of the geometry of these motions is induced compared to the pure phospholipid bilayers.…”

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Effects of cholesterol or gramicidin on slow and fast motions of phospholipids in oriented bilayers.

Peng

Simplăceanu²,

Dowd³

et al. 1989

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

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Nuclear spin-lattice relaxation both in the rotating frame and in the laboratory frame is used to investigate the slow and fast molecular motions of phospholipids in oriented bilayers in the liquid crystalline phase. The bilayers are prepared from a perdeuterated phospholipid labeled with a pair of 'IF atoms at the 7 position of the 2-sn acyl chain.Phospholipid-cholesterol or phospholipid-gramicidin interactions are characterized by measuring the relaxation rates as a function of the bilayer orientation, the locking field, and the temperature. Our studies show that cholesterol or gramicidin can specifically enhance the relaxation due to slow motions in phospholipid bilayers with correlation times Ts longer than 10-8 sec. The perturbations of the geometry of the slow motions induced by cholesterol are qualitatively different from those induced by gramicidin. In contrast, the presence of cholesterol or gramicidin slightly suppresses the fast motions with correlation times if = 10-9 to 10-10 sec without significantly affecting their geometry. Weak locking-field and temperature dependences are observed for both pure lipid bilayers and bilayers containing either cholesterol or gramicidin, suggesting that the motions of phospholipid acyl chains may have dispersed correlation times.To establish a relationship among the structure, dynamics, and function of biological membranes requires knowledge of (i) the packing and motion of phospholipid molecules in a membrane and (ii) the mechanisms for lipid-sterol and lipidprotein interactions. During the last three decades, considerable efforts have been devoted to the biophysical studies of phospholipid bilayers, which are often viewed as a simplified model of natural membranes (1). Although the static properties of a lipid bilayer, such as the conformation and order ofphospholipids, have been carefully characterized (2, 3), the dynamic behavior of phospholipids in a bilayer environment is less well understood (4).The physical state of a phospholipid bilayer under physiological conditions is that of a lyotropic liquid crystal surrounded by water molecules. Due to the amorphous packing and prevalence of molecular motions, high-resolution x-ray diffraction cannot be applied to lipid bilayers in a liquid crystalline phase. Hence, magnetic resonance, which can give both static and dynamic information, is of vital importance in the field of membrane biophysics. In particular, when combined with isotopic labeling, nuclear relaxation becomes a unique technique which can monitor the microscopic dynamics of a specific site within a macromolecule or a supermolecular assembly. Normally, the spin-lattice relaxation in the laboratory frame (T1) is sensitive to molecular motions on the time scale of 10-1o to 10-1 sec, while the spin-lattice relaxation in the rotating frame (T1p) is sensitive to motions on the time scale of 10-6 to 10-4 sec (5).A number of nuclear magnetic resonance (NMR) investigations have focused on the molecular motions of phospholipids in a pure lipid bilayer, an...

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confidence: 99%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Effects of cholesterol or gramicidin on slow and fast motions of phospholipids in oriented bilayers.

Peng

Simplăceanu²,

Dowd³

et al. 1989

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

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“…4 show the prediction for the case of a fixed headgroup tilt over the sample for two positions of the rotation axis. It is expected that in addition to the fast axially symmetric rotation there exist a rich array of slow motions of the lipid molecule as a whole and of various segments of the lipid macromolecule (17,(21)(22)(23). The effects of slower motions are included in this model by allowing the values of a and (# to vary over a specified range with equal weighting for simplicity.…”

Section: Modeling the Relaxationmentioning

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Dynamics of the phosphate group in phospholipid bilayers. A 31P angular dependent nuclear spin relaxation time study

Milburn

Jeffrey

1989

Biophysical Journal

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To understand 31P relaxation processes and hence molecular dynamics in the phospholipid multilayer it is important to measure the dependence of the 31P spin-lattice relaxation time on as many variables as the physical system allows. Such measurements of the 31P spin-lattice relaxation rate have been reported both as a function of Larmor frequency and temperature for egg phosphatidylcholine liposomes (Milburn, M.P., and K.R. Jeffrey. 1987. Biophys. J. 52:791-799). In principle, the spin-lattice relaxation rate in an anisotropic environment such as a bilayer will be a function of the angle between the bilayer normal and the magnetic field. However, the measurement of this angular dependence has not been possible because the rapid (on the time-scale of the spin-lattice relaxation rate) diffusion of the lipid molecules over the curved surface of the liposome average this dependence (Milburn, M.P., and K.R. Jeffrey. 1987. Biophys. J. 52:791-799; Brown, M.F., and J.H. Davis. 1981. Chem. Phys. Lett. 79:431-435). This paper reports the results of the measurement of the 31P spin-lattice relaxation rate as a function of this angle, beta', (the angle between the bilayer normal and the external magnetic field) using samples oriented between glass plates. These measurements were made at high field (145.7 MHz) where the spin-lattice relaxation processes are dominated by the chemical shielding interaction (Milburn, M.P., and K.R. Jeffrey. 1987. Biophys. J. 52:791-799). A model of molecular motion that includes a fast axially symmetric rotation of the phosphate group (tau i approximately 10(-9) s) and a wobble of the head group tilt with respect to this rotation axis has been used to describe both the angular dependence of the spin-lattice relaxation and the spectral anisotropy. Cholesterol is seen to have a negligible effect on the motional properties of the phospholipid phosphate segment as measured by the orientation dependence of the spin-lattice relaxation.

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Bilayer Membranes: Proton and Fluorine-19 NMR

Pace

2007

Encyclopedia of Magnetic Resonance

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Rotating-frame relaxation studies of slow motions in fluorinated phospholipid model membranes

Cited by 28 publications

References 33 publications

Effects of cholesterol or gramicidin on slow and fast motions of phospholipids in oriented bilayers.

Effects of cholesterol or gramicidin on slow and fast motions of phospholipids in oriented bilayers.

Dynamics of the phosphate group in phospholipid bilayers. A 31P angular dependent nuclear spin relaxation time study

Bilayer Membranes: Proton and Fluorine-19 NMR

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