Solid/liquid intermolecular transfer of dynamic nuclear polarization. Enhanced flowing fluid proton NMR signals via immobilized spin labels

Gitti, Rossitza K.; Wild, Christopher; Tsiao, C.; Zimmer, K.; Glass, T. E.; Dorn, Harry C.

doi:10.1021/ja00215a047

Cited by 50 publications

(55 citation statements)

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“…Initially, the polarization and detection was performed in the same magnet, at a frequency of 9.3 GHz (0.35 T, 14 MHz for 1 H) and enhancement factors for 1 H of up to ε = −90 were obtained. 23,84 Later, the detection was performed at a magnetic field of 4.7 T (200 MHz for 1 H) in a separate magnet 85 yielding enhancement factors of ε = −30. In these experiments, the polarizing agent was either diluted in the sample (liquid-liquid intermolecular transfer, L 2 IT) or immobilized on silica gel (solid-liquid intermolecular transfer, SLIT).…”

Section: B Dnp In Liquid Phasementioning

confidence: 99%

“…1 The validity of this suggestion was vigorously debated until Carver and Slichter reported an experiment in which they polarized Li ( Ref. 2 ) and later 23 Na and 1 H nuclei, 3 achieving signal enhancements of ∼100. This experiment, now known as the Overhauser effect (OE) and widely used in solution NMR experiments for measuring 1 H-1 H distances, was the first demonstration of dynamic nuclear polarization (DNP).…”

Section: Introduction/backgroundmentioning

confidence: 99%

“…Further work was done by Mueller-Warmuth et al ,22 who focused on the influence of molecular motion on the electron OE. More recent efforts to polarize liquids have utilized flow techniques 23,24 or approaches where the sample is polarized as a solid at low temperatures and dissolved or melted and the liquid-state spectrum observed. 25,26 Finally, we note that high nuclear spin polarizations can also be created by several other methods such as polarization transfer from optically excited states or polarized noble gases.…”

Section: Introduction/backgroundmentioning

confidence: 99%

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Dynamic nuclear polarization at high magnetic fields

Maly¹,

Debelouchina²,

Bajaj³

et al. 2008

The Journal of Chemical Physics

797

847

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Dynamic nuclear polarization (DNP) is a method that permits NMR signal intensities of solids and liquids to be enhanced significantly, and is therefore potentially an important tool in structural and mechanistic studies of biologically relevant molecules. During a DNP experiment, the large polarization of an exogeneous or endogeneous unpaired electron is transferred to the nuclei of interest (I) by microwave (μw) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (γ e /γ l ), being ∼660 for protons. In the early 1950s, the DNP phenomenon was demonstrated experimentally, and intensively investigated in the following four decades, primarily at low magnetic fields. This review focuses on recent developments in the field of DNP with a special emphasis on work done at high magnetic fields (≥5 T), the regime where contemporary NMR experiments are performed. After a brief historical survey, we present a review of the classical continuous wave (cw) DNP mechanisms-the Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in μw and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments.

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Section: B Dnp In Liquid Phasementioning

confidence: 99%

Section: Introduction/backgroundmentioning

confidence: 99%

Section: Introduction/backgroundmentioning

confidence: 99%

See 1 more Smart Citation

Dynamic nuclear polarization at high magnetic fields

Maly¹,

Debelouchina²,

Bajaj³

et al. 2008

The Journal of Chemical Physics

797

847

View full text Add to dashboard Cite

show abstract

“…Immobilization of radicals on solid materials, such as silica gels or thermoresponsive polymers (30)(31)(32), has been reported for room temperature Overhauser DNP of liquid water. More recently, low temperature DNP at T = 4.2 K was shown by exploiting electron spins at dangling bond sites near the surface of silicon nanoparticles, producing, however, only modest enhancements (∼2) (33).…”

mentioning

confidence: 99%

Hybrid polarizing solids for pure hyperpolarized liquids through dissolution dynamic nuclear polarization

Gajan

Bornet

Vuichoud

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

104

117

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Hyperpolarization of substrates for magnetic resonance spectroscopy (MRS) and imaging (MRI) by dissolution dynamic nuclear polarization (D-DNP) usually involves saturating the ESR transitions of polarizing agents (PAs; e.g., persistent radicals embedded in frozen glassy matrices). This approach has shown enormous potential to achieve greatly enhanced nuclear spin polarization, but the presence of PAs and/or glassing agents in the sample after dissolution can raise concerns for in vivo MRI applications, such as perturbing molecular interactions, and may induce the erosion of hyperpolarization in spectroscopy and MRI. We show that D-DNP can be performed efficiently with hybrid polarizing solids (HYPSOs) with 2,2,6,6-tetramethyl-piperidine-1-oxyl radicals incorporated in a mesostructured silica material and homogeneously distributed along its pore channels. The powder is wetted with a solution containing molecules of interest (for example, metabolites for MRS or MRI) to fill the pore channels (incipient wetness impregnation), and DNP is performed at low temperatures in a very efficient manner. This approach allows high polarization without the need for glass-forming agents and is applicable to a broad range of substrates, including peptides and metabolites. During dissolution, HYPSO is physically retained by simple filtration in the cryostat of the DNP polarizer, and a pure hyperpolarized solution is collected within a few seconds. The resulting solution contains the pure substrate, is free from any paramagnetic or other pollutants, and is ready for in vivo infusion.D-DNP | NMR signal enhancement | molecular imaging | mesostructured hybrid silica | porous materials D issolution dynamic nuclear polarization (D-DNP) (1, 2) usually requires freezing molecules of interest, such as metabolites, together with persistent free radicals often called polarizing agents (PA) in a glassy matrix at very low temperatures (1 < T < 4 K), so that their nuclear spin polarization can be enhanced by up to four to five orders of magnitude. Such enhancements are achieved by saturating the ESR transitions of the PAs. D-DNP is generally performed in moderate magnetic fields (B 0 = 3.35 or in this study, 6.7 T) and followed by rapid dissolution of the frozen sample with a burst of superheated water to give highly polarized solutions. Applications include detection of intermediates in chemical reactions (3-5), protein folding in real time (6), and detection of cancer by monitoring abnormal rates of metabolic reactions in humans (7). PAs with narrow EPR lines, such as trityl radicals, are usually used for the direct polarization of 13 C nuclei (2). In practice, polarizations P( 13 C) of 20% or higher can be obtained after dissolution. We have recently shown that DNP of 13 C can be significantly accelerated by combining increased magnetic fields with polarization of 1 H rather than 13 C [using nitroxide radicals, such as 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO), with broader ESR lines than trityl radicals] followed by Hartmann-Hahn C. In ...

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“…The positive DNP effect is strong evidence for the presence of an electron-nuclear scalar interaction at solid-liquid interface. To date, only a few studies have been published of solid-liquid energy transfer between sublevels in magnetic spin systems consisting of species with different gyromagnetic ratios [2][3]. All of these have described the dominant "solid-state" DNP effect due to pure dipole-dipole (through space) intermolecular interactions, such as those observed between free radical labels immobilized on a silica gel surface and solvent protons [2].…”

Section: Introductionmentioning

confidence: 99%

Coal and Coal Constituent Studies by Advanced Emr Techniques

Belford¹,

Clarkson²

1997

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Advanced electronic magnetic resonance (EMR) methods are used to examine properties of coals, chars, and molecular species related to constituents of coal. During this grant period, progress was made on setting up a separate high frequency EMR system particularly appropriate for such studies and exploring the use of low-frequency dynamic nuclear polarization (DNP) to examine the interaction between fluids such as water and the surface of suspended char particles. W-band (100 Ghz) electronic magnetic resonance (EMR, EPR, or ESR) spectroscopy offers the extremely high resolution to discriminate among very similar chemical species that are constituents of coals and closely related materials such as chars and therefore to provide clues about chemical structures as well as an analytical tool. A W-band spectrometer exists in this laboratory, but as described in the proposal for this project, one of the first tasks was to set up another W-band station that would be particularly appropriate for study of such materials. This task has been progressing very well in the first six months of the project.This report focuses on a new and exciting EMR technique -very low frequency pulsed dynamic nuclear polarization spectroscopy -for the study of the interfaces between coal-like particles and the water medium in which they are suspended. Here is described the discovery by this technique of a transient chemical interaction between certain char particles and the hydrogen atoms of water molecules in the bulk.

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Solid/liquid intermolecular transfer of dynamic nuclear polarization. Enhanced flowing fluid proton NMR signals via immobilized spin labels

Cited by 50 publications

References 0 publications

Dynamic nuclear polarization at high magnetic fields

Dynamic nuclear polarization at high magnetic fields

Hybrid polarizing solids for pure hyperpolarized liquids through dissolution dynamic nuclear polarization

Coal and Coal Constituent Studies by Advanced Emr Techniques

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