Proton Spin Diffusion in Polyethylene as a Function of Magic-Angle Spinning Rate. A Phenomenological Approach

2008 ◽  
Vol 112 (6) ◽  
pp. 1228-1233 ◽  
Author(s):  
Zhenlong Jia ◽  
Lili Zhang ◽  
Qun Chen ◽  
E. W. Hansen
Keyword(s):  
Spin Diffusion ◽  
Phenomenological Approach ◽  
Magic Angle Spinning ◽  
Proton Spin ◽  
Magic Angle ◽  
Angle Spinning

scholarly journals Full-length Vpu and human CD4(372–433) in phospholipid bilayers as seen by magic angle spinning NMR

2013 ◽  
Vol 394 (11) ◽  
pp. 1453-1463 ◽  
Author(s):  
Hoa Q. Do ◽  
Marc Wittlich ◽  
Julian M. Glück ◽  
Luis Möckel ◽  
Dieter Willbold ◽  
...  
Keyword(s):  
Amino Acid ◽  
Lipid Bilayers ◽  
Spin Diffusion ◽  
Magic Angle Spinning ◽  
Proton Spin ◽  
Phospholipid Bilayers ◽  
Amino Acid Type ◽  
Magic Angle ◽  
Amino Acid Residues ◽  
Angle Spinning

Abstract HIV-1 Vpu and CD4(372–433), a peptide comprising the transmembrane and cytoplasmic domain of human CD4, were recombinantly expressed in Escherichia coli, uniformly labeled with 13C and 15N isotopes, and separately reconstituted into phospholipid bilayers. Highly resolved dipolar cross-polarization (CP)-based solid-state NMR spectra of the two transmembrane proteins were recorded under magic angle sample spinning. Partial assignment of 13C resonances was achieved. Site-specific assignments were obtained for 13 amino acid residues of CD4(372–433) and two Vpu residues. Additional amino acid type-specific assignments were achieved for 10 amino acid spin systems for both CD4(372–433) and Vpu. Further, structural flexibility was probed with different dipolar recoupling techniques, and the correct insertion of the transmembrane domains into the lipid bilayers was confirmed by proton spin diffusion experiments.

scholarly journals CP MAS kinetics and impedance spectroscopy studies of local disorder in low-dimensional H-bonded proton-conducting materials

2019 ◽  
Vol 59 (3) ◽  
Author(s):  
Laurynas Dagys ◽  
Sergejus Balčiūnas ◽  
Jûras Banys ◽  
Feliksas Kuliešius ◽  
Vladimir Chizhik ◽  
...  
Keyword(s):  
Impedance Spectroscopy ◽  
Spin Diffusion ◽  
Lattice Relaxation ◽  
Magic Angle Spinning ◽  
Proton Spin ◽  
Spin Lattice Relaxation ◽  
Magic Angle ◽  
Coupling Constant ◽  
Spin Lattice ◽  
Local Disorder

The 1H–13C cross-polarization magic angle spinning (CP MAS) kinetics was studied in poly(vinyl phosphonic acid) (pVPA), i.e. material with high degrees of freedom of proton motion along H-bonded chains. It has been shown that the CP kinetic data for the adjacent 1H–13C spin pairs can be described in the frame of the isotropic spin-diffusion approach. The rates of spin diffusion and spin-lattice relaxation as well as the parameters accounting for spin coupling and the effective size of spin clusters have been determined. The local order parameter S ≈ 0.63±0.02, determined as the ratio of the measured dipolar 1H–13C coupling constant and the calculated static dipolar coupling constant, is significantly lower than the values deduced for related sites in other polymers and in series of amino acids. This means that the local disorder of the C–H bonds in pVPA is between those for rather rigid C–H bond configurations having S = 0.8–1.0 and highly disordered –CH3 groups (S ~ 0.4). This effect can be attributed to the presence of the proton transfer path where proton motion is easy to activate. The activation energy for the proton motion Ea = 59±7 kJ/mol was determined from the impedance spectroscopy data analysing the temperature and frequency dependences of the complex dielectric permittivity of pVPA. The rates of proton spin-lattice relaxation and spin diffusion are of the same order and both run in the time scale of milliseconds.

MIRROR recoupling and its application to spin diffusion under fast magic-angle spinning

2008 ◽  
Vol 460 (1-3) ◽  
pp. 278-283 ◽  
Author(s):  
Ingo Scholz ◽  
Matthias Huber ◽  
Theofanis Manolikas ◽  
Beat H. Meier ◽  
Matthias Ernst
Keyword(s):  
Spin Diffusion ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Angle Spinning ◽  
Fast Magic Angle Spinning

Electron-driven spin diffusion supports crossing the diffusion barrier in MAS DNP

2018 ◽  
Vol 20 (16) ◽  
pp. 11418-11429 ◽  
Author(s):  
Johannes J. Wittmann ◽  
Michael Eckardt ◽  
Wolfgang Harneit ◽  
Björn Corzilius
Keyword(s):  
Dynamic Nuclear Polarization ◽  
Diffusion Barrier ◽  
Nuclear Polarization ◽  
Spin Diffusion ◽  
Hyperfine Interactions ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Diffusion Rates ◽  
Angle Spinning

Hyperfine interactions can quench homonuclear spin-diffusion in the direct vicinity of a polarizing agent in dynamic nuclear polarization (DNP). However, under magic-angle spinning (MAS), the same interactions may also enhance the spin-diffusion rates through an electron-driven spin diffusion (EDSD) mechanism introduced here.

scholarly journals Direct observation of hyperpolarization breaking through the spin diffusion barrier

2021 ◽  
Vol 7 (18) ◽  
pp. eabf5735
Author(s):  
Quentin Stern ◽  
Samuel François Cousin ◽  
Frédéric Mentink-Vigier ◽  
Arthur César Pinon ◽  
Stuart James Elliott ◽  
...  
Keyword(s):  
Diffusion Barrier ◽  
Nuclear Polarization ◽  
Spin Diffusion ◽  
Magic Angle Spinning ◽  
Resonance Spectroscopy ◽  
Magic Angle ◽  
Paramagnetic Centers ◽  
Static Mode ◽  
Angle Spinning ◽  
Marked Dependence

Dynamic nuclear polarization (DNP) is a widely used tool for overcoming the low intrinsic sensitivity of nuclear magnetic resonance spectroscopy and imaging. Its practical applicability is typically bounded, however, by the so-called “spin diffusion barrier,” which relates to the poor efficiency of polarization transfer from highly polarized nuclei close to paramagnetic centers to bulk nuclei. A quantitative assessment of this barrier has been hindered so far by the lack of general methods for studying nuclear polarization flow in the vicinity of paramagnetic centers. Here, we fill this gap and introduce a general set of experiments based on microwave gating that are readily implemented. We demonstrate the versatility of our approach in experiments conducted between 1.2 and 4.2 K in static mode and at 100 K under magic angle spinning (MAS)—conditions typical for dissolution DNP and MAS-DNP—and directly observe the marked dependence of polarization flow on temperature.

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