Protein Reorientation and Bound Water Molecules Measured by 1H Magnetic Spin-Lattice Relaxation

Van-Quynh, A.; Willson, Steven; Bryant, Robert G.

doi:10.1016/s0006-3495(03)74875-9

Cited by 49 publications

(52 citation statements)

References 21 publications

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“…1), simply by performing nuclear magnetic spin-lattice relaxation measurements over a wide-field range, based on the technique of high-resolution field cycling described elsewhere (10,11). Orientation information obtained from relaxation measurements has been a persistent theme in NMR over the years (12), but our approach is based on the symmetry inherent in the accepted model of many phospholipid membranes: (i) the membrane has a well defined time-average surface; (ii) individual phospholipid molecules, on average, are oriented perpendicular to this surface; (iii) each has internal motions occurring with a short timescale, as well as slower motions; and (iv) among the latter, the slowest are likely to include rotational diffusion of the entire molecule about an axis perpendicular to the membrane surface (this axis is known as the ''membrane director'' or below as the ''director''), as well as much slower lateral diffusion about the surface and viscous overall rotation of the vesicle (13).…”

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confidence: 99%

Phospholipid bilayer surface configuration probed quantitatively by ³¹ P field-cycling NMR

Roberts

Redfield

2004

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

175

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31 P relaxation of the diester phosphate of phospholipids in unilamellar vesicles has been studied from 0.004 to 11.7 T. Relaxation at very low fields, below 0.1 T, shows a rate increase that reflects a residual dipolar interaction with neighboring protons, probably dominated by the glycerol C3 protons. This interaction is not fully averaged by faster motion such as rotational diffusion perpendicular to the membrane surface. The remaining dipolar interaction, modulated by overall rotational diffusion of the vesicle and lateral diffusion of the lipid molecules, is responsible for the very low-field relaxation. These measurements yield a good estimate of the time-average angle between the membrane surface and the vector connecting the phosphorus to the glycerol C3 dynamics ͉ membranes ͉ phosphorus M uch remains to be known about the details of the configuration and dynamics of the phosphodiester region of phospholipid bilayer membranes, despite a large body of work (1, 2). Yet such knowledge is likely to be very useful in understanding how proteins and assemblies interact with this interfacial region. For example, there is indirect evidence that the peripheral membrane protein phosphatidylinositol-specific phospholipase inserts a tryptophan residue into a phosphatidylcholine membrane surface, which in turn activates the enzyme toward its substrates, but how this happens in detail is unknown (3, 4).The lack of structural information for phospholipid polar and interfacial moieties results from the difficulty in obtaining crystals and making other ordered structures that are necessary for most structural techniques. Even when available, the resemblance of such ordered structures to membranes functioning in vivo can be questioned. Modern methods of NMR spectroscopy are generally difficult to apply to this problem, mainly because of the slow rate of tumbling of molecules in reasonable analogs of biological membranes such as vesicles. Most NMR studies ( 1 H, 13 C, and 2 H) of membranes have focused on acyl chain dynamics (5-7). Phosphorus-31 NMR, which would appear ideally suited for obtaining information on the phosphodiester linkage conformation and dynamics, has seen limited use, because 31 P resonances in phospholipid aggregates exhibit a large linewidth due to their chemical-shift anisotropy (CSA) [although this property had made this nucleus very useful in characterizing the phase behavior of phospholipid bilayers (5)]. 31 P chemical shifts in phosphodiesters embedded in membranes do reflect orientation of chemical bonds relative to the membrane surface but not in a very usefully specific way. Structures deduced from other NMR data suffer from unknown dynamic averaging effects. Computer simulations show great promise to eventually give completely detailed information (8, 9) but still need to be validated with quantitative experiments.As a contribution to this problem, we have estimated the angle PH between the vector connecting the phosphorus to its nearest protons and the vector perpendicular to the membrane sur...

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confidence: 99%

Phospholipid bilayer surface configuration probed quantitatively by ³¹ P field-cycling NMR

Roberts

Redfield

2004

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

175

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“…[4][5][6] It would be highly desirable to have complementary information directly from the protons of the protein, but this has been impractical so far owing to the low sensitivity of the available instrumentation. Protein 1 H relaxation data have been reported only on protein solutions of concentrations !…”

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confidence: 99%

“…Note that the R 1 values at low field are on the order of 10 2 s À1 , whereas they decrease to essentially zero at high field. Relaxation can be interpreted with an equation of the type [1,6] …”

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confidence: 99%

NMR Spectroscopic Detection of Protein Protons and Longitudinal Relaxation Rates between 0.01 and 50 MHz

et al. 2005

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Nuclear magnetic relaxation data of water nuclei at variable fields provide valuable information on the dynamics of watersolute interactions. [1][2][3] However, information can be collected only within certain field ranges in which the nuclear relaxation rates are field-dependent owing to the dispersion of the spectral density, J(w,t). The dispersion depends on the type of motion and on the observed nucleus. The most informative 1 H NMR spectroscopic frequency range for rotational motions is centered around 10 MHz for small proteins (M W % 10 4 Da) and smaller frequencies for larger proteins and protein aggregates. Of course, resolution is low at these fields and in practice only one signal (or an unresolved signal envelope) can be detected. Furthermore, only the abundant water protons can be conveniently studied under such low sensitivity.Relaxation of the isotopes 17 O and 2 H in enriched water can also be studied; [1] in these cases the centers of the informative field ranges increase by a factor % 7 with respect to 1 H as a result of the magnetogyric ratios of 17 O and 2 H. Because water interacts with proteins, such relaxation studies provide direct information on the nature of water-protein dynamics, but give only indirect information on the protein itself.[4-6] It would be highly desirable to have complementary information directly from the protons of the protein, but this has been impractical so far owing to the low sensitivity of the available instrumentation. Protein 1 H relaxation data have been reported only on protein solutions of concentrations ! 35 % by mass, [7,8] far from physiological conditions. Improvements in field-cycling technology [9][10][11][12] have led to the production of instrumentation [13] with a % 10-fold increase in the signal-to-noise ratio, [14] with which direct protein 1 H detection can be attempted for protein concen- Figure 1. Protein 1 H relaxation dispersions for lysozyme solutions (2.8 mm in D 2 O) at a) pH* 3.5, and b) pH* 9.0 (pH=pH-meter reading in D20 solution). The time decay of the collective protein 1 H magnetization at 0.1 MHz and its single-exponential fit are shown in the inset of part a). Theoretical relaxation rates were obtained through singleexponential fits of time decays of collective protein 1 H magnetization calculated from the known protein structure of lysozyme [17] and a complete relaxation matrix (CORMA) analysis.[18] Only exchangeable NH protons from secondary structure elements ( % 50 % of total) were included, whereas all other exchangeable proton positions were assumed to be deuterated. Inclusion of either all or none of the NH protons affected the calculated rates by AE 2 %. The theoretical lowfield hE 2 i values obtained in this way were used to fit Equation (1) to the data (solid lines). The dotted lines represent data fits with two J-(w,t) terms in Equation (1) ( Table 1). Panel c) shows the protein 1 H relaxation dispersion for a solution of a-synuclein in D 2 O (1.4 mm, pH* 7.1). The solid and dotted lines represent fits with one or two J-(...

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“…With both effects minimized, a number of protein solutions were investigated and shown to yield simple Lorentzian dispersion curves. 25,31 For each protein the MRD results were consistent with a small number of slowly exchanging water molecules associated with the protein molecule. 25,30 The influence of protein aggregation on MRD profiles also has been exploited recently to study self-association of hen-egg-white lysozyme (HEWL) in solution.…”

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confidence: 58%

Cross‐relaxation bottleneck in water–lysozyme proton magnetization exchange

Kakule¹,

Sharp²,

Schreiner³

et al. 2006

Biopolymers

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The proton spin-lattice relaxation parameters in natural and deuterated lysozyme solutions have been measured as a function of temperature (0-50 degrees C). The variation of the apparent magnitudes of the water proton magnetizations in the solutions with temperature indicates that magnetic coupling mixes protein and water proton magnetizations. The results are consistent with an exchange cross-relaxation model (Hills, B. P., Mol Phys 1992, 76, 489-508) in which the cross-relaxation acts between the labile and nonlabile protons, rather than between water and protein protons. Although this cross-relaxation pathway clearly affects the observed magnetization fractions in this protein solution, its influence on the relaxation rates is less apparent.

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Protein Reorientation and Bound Water Molecules Measured by 1H Magnetic Spin-Lattice Relaxation

Cited by 49 publications

References 21 publications

Phospholipid bilayer surface configuration probed quantitatively by ³¹ P field-cycling NMR

Phospholipid bilayer surface configuration probed quantitatively by ³¹ P field-cycling NMR

NMR Spectroscopic Detection of Protein Protons and Longitudinal Relaxation Rates between 0.01 and 50 MHz

Cross‐relaxation bottleneck in water–lysozyme proton magnetization exchange

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Protein Reorientation and Bound Water Molecules Measured by 1H Magnetic Spin-Lattice Relaxation

Cited by 49 publications

References 21 publications

Phospholipid bilayer surface configuration probed quantitatively by 31 P field-cycling NMR

Phospholipid bilayer surface configuration probed quantitatively by 31 P field-cycling NMR

NMR Spectroscopic Detection of Protein Protons and Longitudinal Relaxation Rates between 0.01 and 50 MHz

Cross‐relaxation bottleneck in water–lysozyme proton magnetization exchange

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Phospholipid bilayer surface configuration probed quantitatively by ³¹ P field-cycling NMR

Phospholipid bilayer surface configuration probed quantitatively by ³¹ P field-cycling NMR