Mechanism of 1 H– 14 N cross-relaxation in immobilized proteins

Sunde, Erik Persson; Halle, Bertil

doi:10.1016/j.jmr.2010.01.008

Cited by 55 publications

(73 citation statements)

References 71 publications

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“…Although the exact origin of the quadrupolar peaks is not certain, physical considerations suggest that it originates from amide groups (22). Even though most proteins contain amide groups, not all of them show quadrupolar peaks.…”

Section: Theorymentioning

confidence: 99%

“…Even though most proteins contain amide groups, not all of them show quadrupolar peaks. Several conditions are necessary for the transfer of magnetization from a dipole to a quadrupole: the protein motion must be restricted (gel or solid phase) and the amide group should attract water molecules with a residence time long enough to allow magnetization transfer but also short enough to relax a large number of water protons (typically about 1 μs; Ref 22…”

Section: Theorymentioning

confidence: 99%

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Detection of osteoarthritis in knee and hip joints by fast field‐cycling NMR

Broche

Ashcroft

Lurie

2011

Magnetic Resonance in Med

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It is known that in the early stages of osteoarthritis, the concentration of glycan proteins decreases in articular cartilage. This phenomenon is under active research to develop a means to characterize osteoarthritis accurately in the early stages of the disease, when still reversible. However, no method of quantification has yet shown clear success in this area. In this article, we propose a novel approach to detect glycan depletion using fast field-cycling NMR. This technique was previously reported to allow noninvasive measurement of protein concentration via the 14 N quadrupolar relaxation in certain amide groups. We have demonstrated that the articular cartilage exhibits clear quadrupolar peaks that can be measured by a benchtop fast field-cycling NMR device and which changes significantly between normal and diseased tissues (P < 0.01). This signal is probably glycan specific. The method may have potential for early evaluation of osteoarthritis in patients on fast field-cycling-MRI scanners currently under evaluation in the authors' laboratory. Magn Reson Med 68:358-362,

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Section: Theorymentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

Detection of osteoarthritis in knee and hip joints by fast field‐cycling NMR

Broche

Ashcroft

Lurie

2011

Magnetic Resonance in Med

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“…In the latter case, the dipole coupling is expected to be averaged out by fast (microsecond) quadrupolar 14 N relaxation rather than by proton exchange, which typically is much slower. 29 Because the I spin then undergoes "dipolar relaxation of the second kind," the mean survival time τ A does not play the role of correlation time, as it does in the EMOR mechanism. For amide protons, τ A is too long for this process to contribute significantly to I-spin relaxation.…”

Section: Exchange Scenariosmentioning

confidence: 99%

“…On the other hand, a more rapidly exchanging nearby proton, dipole-coupled to the amide proton, might mediate resonant cross-relaxation at the discrete MHz frequencies that correspond to transitions between the three nondegenerate eigenstates of the static 14 N spin Hamiltonian. 29 Finally, I/S exchange refers to the case where both spins exchange independently, as when both I and S are labile protons. The dipole coupling is then averaged to zero by exchange of either spin.…”

Section: Exchange Scenariosmentioning

confidence: 99%

Nuclear magnetic relaxation induced by exchange-mediated orientational randomization: Longitudinal relaxation dispersion for a dipole-coupled spin-1/2 pair

Chang

Halle

2013

The Journal of Chemical Physics

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In complex biological or colloidal samples, magnetic relaxation dispersion (MRD) experiments using the field-cycling technique can characterize molecular motions on time scales ranging from nanoseconds to microseconds, provided that a rigorous theory of nuclear spin relaxation is available. In gels, cross-linked proteins, and biological tissues, where an immobilized macromolecular component coexists with a mobile solvent phase, nuclear spins residing in solvent (or cosolvent) species relax predominantly via exchange-mediated orientational randomization (EMOR) of anisotropic nuclear (electric quadrupole or magnetic dipole) couplings. The physical or chemical exchange processes that dominate the MRD typically occur on a time scale of microseconds or longer, where the conventional perturbation theory of spin relaxation breaks down. There is thus a need for a more general relaxation theory. Such a theory, based on the stochastic Liouville equation (SLE) for the EMOR mechanism, is available for a single quadrupolar spin I = 1. Here, we present the corresponding theory for a dipole-coupled spin-1/2 pair. To our knowledge, this is the first treatment of dipolar MRD outside the motional-narrowing regime. Based on an analytical solution of the spatial part of the SLE, we show how the integral longitudinal relaxation rate can be computed efficiently. Both like and unlike spins, with selective or non-selective excitation, are treated. For the experimentally important dilute regime, where only a small fraction of the spin pairs are immobilized, we obtain simple analytical expressions for the auto-relaxation and cross-relaxation rates which generalize the well-known Solomon equations. These generalized results will be useful in biophysical studies, e.g

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“…24 and 25 to an arbitrary spin quantum number. QRE effects are reported in the literature, [26][27][28] for instance, for proteins 14,29,30 (recently, also in the context of medical applications 28 ligands and three structurally non-equivalent imidazolium cations showing orientational disorder. The structural properties suggest a complex and interesting dynamics of the compound, which we intend to reveal profiting from the potential of 1 H NMR relaxometry.…”

Section: Introductionmentioning

confidence: 97%

Dynamics of [C3H5N2]6[Bi4Br18] by means of 1H NMR relaxometry and quadrupole relaxation enhancement

Masierak

Florek–Wojciechowska

Oglodek

et al. 2015

The Journal of Chemical Physics

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(1)H spin-lattice field cycling relaxation dispersion experiments in the intermediate phase II of the solid [C3H5N2]6[Bi4Br18] are presented. Two motional processes have been identified from the (1)H spin-lattice relaxation dispersion profiles and quantitatively described. It has been concluded that these processes are associated with anisotropic reorientations of the imidazolium ring, characterized by correlation times of the order of 10(-8) s-10(-9) s and of about 10(-5) s. Moreover, quadrupole relaxation enhancement (QRE) effects originating from slowly fluctuating (1)H-(14)N dipolar interactions have been observed. From the positions of the relaxation maxima, the quadrupole coupling parameters for the (14)N nuclei in [C3H5N2]6[Bi4Br18] have been determined. The (1)H-(14)N relaxation contribution associated with the slow dynamics has been described in terms of a theory of QRE [Kruk et al., Solid State Nucl. Magn. Reson. 40, 114 (2011)] based on the stochastic Liouville equation. The shape of the QRE maxima (often referred to as "quadrupole peaks") has been consistently reproduced for the correlation time describing the slow dynamics and the determined quadrupole coupling parameters.

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Mechanism of 1 H– 14 N cross-relaxation in immobilized proteins

Cited by 55 publications

References 71 publications

Detection of osteoarthritis in knee and hip joints by fast field‐cycling NMR

Detection of osteoarthritis in knee and hip joints by fast field‐cycling NMR

Nuclear magnetic relaxation induced by exchange-mediated orientational randomization: Longitudinal relaxation dispersion for a dipole-coupled spin-1/2 pair

Dynamics of [C3H5N2]6[Bi4Br18] by means of 1H NMR relaxometry and quadrupole relaxation enhancement

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