Fractional Spin‐Labeling of Polymers for Enhancing NMR Sensitivity by Solvent‐Free Dynamic Nuclear Polarization

Vitzthum, Veronika; Borcard, Françoise; Jannin, Sami; Morin, M. Garcia; Miéville, Pascal; Caporini, Marc A.; Sienkiewicz, Andrzej; Gerber‐Lemaire, Sandrine; Bodenhausen, Geoffrey

doi:10.1002/cphc.201100630

Cited by 69 publications

(90 citation statements)

References 21 publications

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“…This solvent-free DNP procedure demonstrated here for materials exhibits similarities with another solvent-free DNP protocol, which has been introduced recently for the DNP of polypeptides [31]. In this work, the molecular entities, unlabeled and labeled with nitroxide radicals, are cocondensed, whereas in reference [31], they were mixed by dissolution and solvent evaporation. In this article, the results of 1 H and 29 Si DNP experiments will be presented for 1 obtained using co-condensation.…”

Section: Introductionmentioning

confidence: 83%

“…This co-condensation procedure can be advantageous, since: (i) it can be applied in principle to nonporous materials or microporous materials exhibiting pore aperture smaller than the smallest dimension of TEMPO and TOTAPOL (about 7 Å ); (ii) it ensures a more homogeneous distribution of organic moieties within the inorganic material than post-synthesis incorporation [30]; (iii) the distance between the unpaired electrons and the silica surface cannot exceed 9 Å , the size of the organic moiety; (iv) this hybrid material allows solvent-free DNP to be tested since the xerogels are dried during the sample preparation [24]. This solvent-free DNP procedure demonstrated here for materials exhibits similarities with another solvent-free DNP protocol, which has been introduced recently for the DNP of polypeptides [31]. In this work, the molecular entities, unlabeled and labeled with nitroxide radicals, are cocondensed, whereas in reference [31], they were mixed by dissolution and solvent evaporation.…”

Section: Introductionmentioning

confidence: 88%

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Solvent-Free High-Field Dynamic Nuclear Polarization of Mesoporous Silica Functionalized with TEMPO

Thankamony

Lafon

et al. 2012

Appl Magn Reson

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We report high-field magic-angle spinning dynamic nuclear polarization (MAS DNP) of mesoporous silica functionalized with nitroxide radicals. These results demonstrate that co-condensation can be employed to incorporate DNP polarizing agents into inorganic materials and that solvent-free DNP is feasible for porous materials. For the investigated material, the direct MAS DNP enhances the 29 Si nuclear magnetic resonance (NMR) spectra, whereas the indirect MAS DNP via protons is inapplicable owing to the inefficiency of 1 H ! 29 Si cross polarization transfer. Furthermore, the 29 Si signals in direct experiments build up in a few seconds at 100 K. This fast polarization buildup improves the NMR sensitivity and will be useful for the investigation of direct DNP below 100 K.

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Section: Introductionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 88%

Solvent-Free High-Field Dynamic Nuclear Polarization of Mesoporous Silica Functionalized with TEMPO

Thankamony

Lafon

et al. 2012

Appl Magn Reson

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“…When the buildup time and T 1 are different, as seen in Figures 4 and 5, a better measure of the improvement in signal-to-noise ratio is sensitivity (S/N*t −1/2 ) rather than enhancement, which in this case is a factor of 128. (One may take more factors into account when calculating improvements from DNP, such as dilution of the sample and bleaching due to the electron spin, as done recently by Jannin et al 69 ) To our knowledge, this is the best gain in sensitivity reported for contemporary DNP experiments using the solid effect with 1 H enhancement at high fields (5 T). Additionally, we see in Figure 6 that as we increase the microwave field strength, we do not yet observe evidence of saturation of the solid effect.…”

Section: Methodsmentioning

confidence: 98%

Solid effect dynamic nuclear polarization and polarization pathways

Smith¹,

Corzilius²,

Barnes³

et al. 2012

The Journal of Chemical Physics

113

143

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Using dynamic nuclear polarization (DNP)/nuclear magnetic resonance instrumentation that utilizes a microwave cavity and a balanced rf circuit, we observe a solid effect DNP enhancement of 94 at 5 T and 80 K using trityl radical as the polarizing agent. Because the buildup rate of the solid effect increases with microwave field strength, we obtain a sensitivity gain of 128. The data suggest that higher microwave field strengths would lead to further improvements in sensitivity. In addition, the observation of microwave field dependent enhancements permits us to draw conclusions about the path that polarization takes during the DNP process. By measuring the time constant for the polarization buildup and enhancement as a function of the microwave field strength, we are able to compare models of polarization transfer, and show that the major contribution to the bulk polarization arises via direct transfer from electrons, rather than transferring first to nearby nuclei and then transferring to bulk nuclei in a slow diffusion step. In addition, the model predicts that nuclei near the electron receive polarization that can relax, decrease the electron polarization, and attenuate the DNP enhancement. The magnitude of this effect depends on the number of near nuclei participating in the polarization transfer, hence the size of the diffusion barrier, their T 1 , and the transfer rate. Approaches to optimizing the DNP enhancement are discussed.

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“…Such SDSL techniques are widely applied in PRE studies. They have also been used in recent liquidstate DNP work [18,19], and may become attractive for solid-state DNP [20]. Once a protein or nucleic acid is spin labeled, further information can be obtained from CW EPR experiments [14] or distance measurements between spin labels by pulsed EPR techniques [21].…”

Section: Introductionmentioning

confidence: 99%

Conformational dynamics and distribution of nitroxide spin labels

Jeschke

2013

Progress in Nuclear Magnetic Resonance Spectroscopy

136

115

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Long-range distance measurements based on paramagnetic relaxation enhancement (PRE) in NMR, quantification of surface water dynamics near biomacromolecules by Overhauser dynamic nuclear polarization (DNP) and sensitivity enhancement by solid-state DNP all depend on introducing paramagnetic species into an otherwise diamagnetic NMR sample. The species can be introduced by site-directed spin labeling, which offers precise control for positioning the label in the sequence of a biopolymer. However, internal flexibility of the spin label gives rise to dynamic processes that potentially influence PRE and DNP behavior and leads to a spatial distribution of the electron spin even in solid samples. Internal dynamics of spin labels and their static conformational distributions have been studied mainly by electron paramagnetic resonance spectroscopy and molecular dynamics simulations, with a large body of results for the most widely applied methanethiosulfonate spin label MTSL. These results are critically discussed in a unifying picture based on rotameric states of the group that carries the spin label. Deficiencies in our current understanding of dynamics and conformations of spin labeled groups and of their influence on NMR observables are highlighted and directions for further research suggested.

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Fractional Spin‐Labeling of Polymers for Enhancing NMR Sensitivity by Solvent‐Free Dynamic Nuclear Polarization

Cited by 69 publications

References 21 publications

Solvent-Free High-Field Dynamic Nuclear Polarization of Mesoporous Silica Functionalized with TEMPO

Solvent-Free High-Field Dynamic Nuclear Polarization of Mesoporous Silica Functionalized with TEMPO

Solid effect dynamic nuclear polarization and polarization pathways

Conformational dynamics and distribution of nitroxide spin labels

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