Dynamic Nuclear Polarization NMR Spectroscopy of Microcrystalline Solids

We systematically studied the enhancement factor (per scan) and the sensitivity enhancement (per unit H} correlation spectra, using, respectively, indirect detection or Carr-Purcell-Meiboom-Gill (CPMG) refocusing to boost signal acquisition. This study highlights opportunities for further improvements through the development of high-field DNP, better polarizing agents, and improved capabilities for low-temperature MAS.time

supporting

confidence: 53%

Section: Contributions To the Global Dnp Enhancementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis of sensitivity enhancement by dynamic nuclear polarization in solid-state NMR: a case study of functionalized mesoporous materials

Kobayashi

Lafon

Thankamony

et al. 2013

“…Note that, in practice, a long T 1 is indeed a key problem for assignments at natural abundance for compounds of unknown structure. Recently introduced impregnation DNP approaches may alleviate this issue in the future 65 . Figure 7 shows the 1 H MAS NMR spectrum and the 13 C CPMAS NMR spectrum for theophylline.…”

Section: D Dft Calculationsmentioning

confidence: 99%

Powder crystallography of pharmaceutical materials by combined crystal structure prediction and solid-state 1H NMR spectroscopy

Baias

Widdifield

Dumez

et al. 2013

Self Cite

159

251

A protocol for the ab initio crystal structure determination of powdered solids at natural isotopic abundance by combining solid-state NMR spectroscopy, crystal structure prediction, and DFT chemical shift calculations was evaluated to determine the crystal structures of four small drug molecules: cocaine, flutamide, flufenamic acid, and theophylline. For cocaine, flutamide and flufenamic acid, we find that the assigned 1 H isotropic chemical shifts provide sufficient discrimination to determine the correct structures from a set of predicted structures using the root-mean-square deviation (rmsd) between experimentally determined and calculated chemical shifts. In most cases unassigned shifts could not be used to determine the structures. This method requires no prior knowledge of the crystal structure, and was used to determine the correct crystal structure to within an atomic rmsd of less than 0.12 Å with respect to the known reference structure. For theophylline, the NMR spectra are too simple to allow for unambiguous structure selection.

“…[46][47][48][49][50] Very recently, application of DNP enhanced MAS NMR spectroscopy on several nanoparticles has been demonstrated, showing the feasibility of the technique for studying such systems. [51][52][53] Here we apply MAS DNP-NMR spectroscopy to investigate site-specific surface and bulk properties of pure (non-functional) as well as arginine-and lysine-functionalized silicon-oxide nanoparticles (Fig. 1).…”

Section: A Introductionmentioning

confidence: 99%

Dynamic nuclear polarization of spherical nanoparticles

Akbey

Altın

Linden

et al. 2013

Spherical silica nanoparticles of various particle sizes (B10 to 100 nm), produced by a modified Stoeber method employing amino acids as catalysts, are investigated using Dynamic Nuclear Polarization (DNP) enhanced Nuclear Magnetic Resonance (NMR) spectroscopy. This study includes ultra-sensitive detection of surface-bound amino acids and their supramolecular organization in trace amounts, exploiting the increase in NMR sensitivity of up to three orders of magnitude via DNP. Moreover, the nature of the silicon nuclei on the surface and the bulk silicon nuclei in the core (sub-surface) is characterized at atomic resolution. Thereby, we obtain unique insights into the surface chemistry of these nanoparticles, which might result in improving their rational design as required for promising applications, e.g. as catalysts or imaging contrast agents. The non-covalent binding of amino acids to surfaces was determined which shows that the amino acids not just function as catalysts but become incorporated into the nanoparticles during the formation process. As a result only three distinct Q-types of silica signals were observed from surface and core regions. We observed dramatic changes of DNP enhancements as a function of particle size, and very small particles (which suit in vivo applications better) were hyperpolarized with the best efficiency. Nearly one order of magnitude larger DNP enhancement was observed for nanoparticles with 13 nm size compared to particles with 100 nm size.We determined an approximate DNP penetration-depth (B4.2 or B5.7 nm) for the polarization transfer from electrons to the nuclei of the spherical nanoparticles. Faster DNP polarization buildup was observed for larger nanoparticles. Efficient hyperpolarization of such nanoparticles, as achieved in this work, can be utilized in applications such as magnetic resonance imaging (MRI). A IntroductionDNP increases the sensitivity of NMR experiments (signal-to-noise ratio, S/N), 1-3 enabling the study of low concentrated systems which were not in the scope of NMR until now. NMR signal enhancement is achieved by transferring large electron polarization to surrounding nuclei via DNP. In the last decade, there has been remarkable progress in solution and solid-state DNP-NMR as well as in imaging through the application of hyperpolarization methods. [4][5][6][7] As pointed out recently, this ''renaissance of DNP'' combined with high magnetic fields will further grow in the coming years, enabling demanding applications with better resolution. 8,9 Materials and biological systems such as membrane or microcrystalline proteins, 10-13 fibrils, 14 ligands bound to receptors, 15 polymers, [16][17][18] surface-bound species, 19-23 and other low concentrated samples were studied beneficially using DNP-NMR. 13,[24][25][26] Cryogenic temperatures are required to slow down nuclear and electron relaxation and to allow an efficient polarization transfer in solid-state DNP NMR experiments. In contrast to biological systems, 15,27-29 most technically relevant materials ...