Anisotropic nuclear spin relaxation of 13C in solid benzene

Gibby, M. G.; Pines, Alexander; Waugh, J. S.

doi:10.1016/0009-2614(72)80276-8

Cited by 53 publications

(16 citation statements)

References 14 publications

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“…However, with the strongly increased polarization of the protons due to DNP, it becomes comparable in size to the direct polarization of the 13 C and thus a major influence on the spectra. From the 180° pulse experiment, it is evident that the indirect channel is related to the proton magnetization, i.e., a heteronuclear cross-relaxation effect in the form of a nuclear Overhauser enhancement (NOE). , While NOE effects are commonly exploited in solution NMR, they are less frequently observed or applied in solid-state NMR (see, e.g., refs − ). The latter is due to the lack of the necessary molecular motions that modulate the heteronuclear dipolar interactions on the time-scale of the 1 H– 13 C zero-quantum and double-quantum transitions, i.e., with correlations times of τ c < 10 –10 s –1 .…”

Section: Discussionmentioning

confidence: 99%

Directly vs Indirectly Enhanced ¹³C in Dynamic Nuclear Polarization Magic Angle Spinning NMR Experiments of Nonionic Surfactant Systems

et al. 2017

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A study of dynamic nuclear polarization (DNP) in polyethylene glycol and related nonionic surfactants is presented. In these experiments, we found the surprising result that DNP enhanced 13 C magic angle spinning (MAS) spectra display two sets of resonances, one with broad and one with sharp spectral features that are 180°opposite in phase. These two sets indicate the presence of a direct polarization transfer channel as expected for 13 C MAS experiments, and a second unexpected indirect polarization transfer channel. Plots of DNP enhancements as a function of applied magnetic field for the two resonances show a superposition of two DNP enhancement profiles for AMUpol in the nonionic surfactant C 10 E 6 . The indirect polarization channel can be suppressed by application of a string of 1 H 180°pulses during 13 C DNP buildup. The presence of direct and indirect polarization channels is observed in a total of four different nonionic surfactants and with three different radicals, showing that these concurring polarization mechanisms are of general nature. Therefore, the presented findings, including the demonstration of how the indirect polarization channel can be suppressed, are of high importance for all future applications of direct 13 C MAS DNP.

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Section: Discussionmentioning

confidence: 99%

Directly vs Indirectly Enhanced ¹³C in Dynamic Nuclear Polarization Magic Angle Spinning NMR Experiments of Nonionic Surfactant Systems

et al. 2017

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“…T 1 THEORETICAL MODEL T 1 theory due to molecular-orientation in solids can be found in literature (28)(29)(30). A T 1 model specifically for a methyl group rotation can also be found in Naito and McDowell (31).…”

Section: T 1 Nmr Experimentsmentioning

confidence: 99%

Insight into the Binding of Antifreeze Proteins to Ice Surfaces via 13C Spin Lattice Relaxation Solid-State NMR

Mao

2006

Biophysical Journal

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The primary sequences of type I antifreeze proteins (AFPs) are Ala rich and contain three 11-residue repeat units beginning with threonine residues. Their secondary structures consist of alpha-helices. Previous activity study of side-chain mutated AFPs suggests that the ice-binding side of type I AFPs comprises the Thr side chains and the conserved i + 4 and i + 8 Ala residues, where i indicates the positions of the Thrs. To find structural evidence for the AFP's ice-binding side, a variable-temperature dependent (13)C spin lattice relaxation solid-state NMR experiment was carried out for two Ala side chain (13)C labeled HPLC6 isoforms of the type I AFPs each frozen in H(2)O and D(2)O, respectively. The first one was labeled on the equivalent 17th and 21st Ala side chains (i + 4, 8), and the second one on the equivalent 8th, 19th, and 30th Ala side chains (i + 6). The two kinds of labels are on the opposite sides of the alpha-helical AFP. A model of Ala methyl group rotation/three-site rotational jump combined with water molecular reorientation was tested to probe the interactions of the methyl groups with the proximate water molecules. Analysis of the T(1) data shows that there could be 10 water molecules closely capping an i + 4 or an i + 8 methyl group within the range of van der Waals interaction, whereas the surrounding water molecules to the i + 6 methyl groups could be looser. This study suggests that the side of the alpha-helical AFP comprising the i + 4 and i + 8 Ala methyl groups could interact with the ice surface in the ice/water interface.

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“…The two sets of oppositely phased 13 C spectral resonances were explained by the superposition of a direct polarization transfer from the electron spin to 13 C (“direct channel”) and an indirect polarization transfer via NOE-type processes between the 13 C and the proton spin reservoir (“indirect channel”). While 1 H– 13 C NOEs in solids have been known for a long time, − they are generally regarded as very ineffective in most solids compared to standard CP-MAS experiments. However, their intensities can be drastically increased with DNP.…”

Section: Introductionmentioning

confidence: 99%

Unusual Local Molecular Motions in the Solid State Detected by Dynamic Nuclear Polarization Enhanced NMR Spectroscopy

Hoffmann

Bothe²,

Gutmann³

et al. 2017

J. Phys. Chem. C

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Polyethylene glycol (PEG) and three related surfactants were studied by dynamic nuclear polarization (DNP) enhanced solid state NMR spectroscopy and differential scanning calorimetry (DSC). DNP enhanced solid state NMR surprisingly reveals the presence of local molecular motions that are normally understood to be inactive at temperatures ∼100 K. This surprising phenomenon could be explained by the experimentally necessary rapid freezing of the studied samples. Specifically, DSC shows that PEG 200 forms a glass upon freezing and that the three PEG-related surfactants are at least partially in a glass state or some other thermodynamic nonequilibrium state when rapidly frozen to the temperatures of the DNP enhanced solid state NMR experiments. This effect of preserving local molar motions by rapid freezing also holds true for solutions of organic solutes in the PEG 200 solvent matrix.

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Anisotropic nuclear spin relaxation of 13C in solid benzene

Cited by 53 publications

References 14 publications

Directly vs Indirectly Enhanced ¹³C in Dynamic Nuclear Polarization Magic Angle Spinning NMR Experiments of Nonionic Surfactant Systems

Directly vs Indirectly Enhanced ¹³C in Dynamic Nuclear Polarization Magic Angle Spinning NMR Experiments of Nonionic Surfactant Systems

Insight into the Binding of Antifreeze Proteins to Ice Surfaces via 13C Spin Lattice Relaxation Solid-State NMR

Unusual Local Molecular Motions in the Solid State Detected by Dynamic Nuclear Polarization Enhanced NMR Spectroscopy

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Anisotropic nuclear spin relaxation of 13C in solid benzene

Cited by 53 publications

References 14 publications

Directly vs Indirectly Enhanced 13C in Dynamic Nuclear Polarization Magic Angle Spinning NMR Experiments of Nonionic Surfactant Systems

Directly vs Indirectly Enhanced 13C in Dynamic Nuclear Polarization Magic Angle Spinning NMR Experiments of Nonionic Surfactant Systems

Insight into the Binding of Antifreeze Proteins to Ice Surfaces via 13C Spin Lattice Relaxation Solid-State NMR

Unusual Local Molecular Motions in the Solid State Detected by Dynamic Nuclear Polarization Enhanced NMR Spectroscopy

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Directly vs Indirectly Enhanced ¹³C in Dynamic Nuclear Polarization Magic Angle Spinning NMR Experiments of Nonionic Surfactant Systems

Directly vs Indirectly Enhanced ¹³C in Dynamic Nuclear Polarization Magic Angle Spinning NMR Experiments of Nonionic Surfactant Systems