Flow dynamic nuclear polarization, a novel method for enhancing NMR signals in flowing fluids

Dorn, Harry C.; Wang, J; Allen, Lance; Sweeney, Dan; Glass, T. E.

doi:10.1016/0022-2364(88)90078-9

Cited by 16 publications

(18 citation statements)

References 7 publications

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“…The dynamic nuclear polarization for a flowing bolus was generated in a low magnetic field (0.34 T) and then rapidly transferred to a monitofing high magnetic field (4.7 T). The flow transfer DNP expe¡ has the additional advantage of efficient removal of heat generated in the microwave field 0310 [9]. In our initial experiments, stable nitroxide radicals immobilized on silica gel were employed to transfer the polarization to a flowing liquid sample (e.g., benzene) [10].…”

Section: Introductionmentioning

confidence: 99%

A model for establishing the ultimate enhancements (A∞) in the low to high magnetic field transfer dynamic nuclear polarization experiment

Tsai

Dorn

1990

Appl Magn Reson

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In a preliminar 3, report, we have demonstrated transfer of a flowing bolus enhanced in low magnetic fields (e.g., 0.33 T) with dynamic nuclear polarization (DNP), but monitored in a high magnetic field (4.7 T). The advantages of the high magnetic field monitoring approach include: 1) greater chemical shift dispersion, and 2) improved signal strength in compa¡ with static low field DNP experiments. In the present study, a model is developed to predict ultimate DNP enhancements (Aoo) in this expefiment for flow liquid/liquid intermolecular transfer (L2IT). L2IT IH and 13C data is obtained for benzene and chloroform in order to test the validity of the model. The ultimate XH and 13C DNP enhancements obtained for benzene/TEMPO ate --150 and --220, respectively. For a chloroform/TEMPO (L2IT) sample, the ultimate enhancements ate close to the tH dipolar (--)30) and the 13C scalar (+2660) limit, respectively. In the latter case, the observed 13C DNP enhancement exceeds the thermal Boltzmann magnetization at 4.7 T by a factor of 21. For a 1-chlorobutane/TEMPO sample selective enhancements were observed at different sites in the molecule. For example, the C-1 carbon exhibits a large scalar enhancement, whereas, the other carbons exhibit dipolar enhancements. Data illustrating the importance of three-spin effects in 13C DNP studies is also presented. Alternative methods of sample transfer from the low to high magnetic field are also discussed.

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Section: Introductionmentioning

confidence: 99%

A model for establishing the ultimate enhancements (A∞) in the low to high magnetic field transfer dynamic nuclear polarization experiment

Tsai

Dorn

1990

Appl Magn Reson

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“…At low μw frequencies (e.g., 9 GHz) polarization in a DNP experiment can be performed in a standard TE 102 rectangular EPR cavity. 24,84 At high frequencies, the cylindrical TE 011 cavity first proposed by Grinberg et al 113 is commonly used in EPR experiments. However, the reduced size of the cylindrical resonator (e.g., 2.8 mm inner diameter at 140 GHz) does not allow a NMR rf coil to be mounted inside the resonator.…”

Section: Probes Used For Dnp Experimentsmentioning

confidence: 99%

“…59,61 In contrast only photo-CIDNP experiments have utilized endogeneous polarizing agents in solids. 82,83 In solution DNP, the polarizing agent can be dissolved in the solvent, 50 attached to a support while the solution flows past it, 24,84,85 or connected to a bulky particle such Si and suspended in solution. 86 Five of the molecules that have been frequently used for polarizing agents in high-field DNP experiments are illustrated in Fig.…”

Section: Polarizing Agentsmentioning

confidence: 99%

“…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%

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Dynamic nuclear polarization at high magnetic fields

Maly¹,

Debelouchina²,

Bajaj³

et al. 2008

The Journal of Chemical Physics

799

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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“…In previous heteroates (4), in vivo organ perfusion studies (5,6), liquid chro-nuclear flow probes, NOE enhancement was unattainable matographic (LC) detection (7,8), and sensitivity enhance-because the sample 1 H irradiation time was too short comment through dynamic electron-nuclear polarization (DNP) pared to T 1 , although spectral decoupling and DEPT experi- (9,10). Continuous-flow NMR of heteronuclei such as 13 C ments (16), which are based on significantly faster effects, (11) and 15 N offers the advantages over 1 …”

Section: H)mentioning

confidence: 97%

NOE Enhancement in Continuous-Flow13C and15N FT NMR Using Upstream1H Preirradiation

Günther

Sudmeier

Albert

et al. 1995

Journal of Magnetic Resonance, Series A

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Flow dynamic nuclear polarization, a novel method for enhancing NMR signals in flowing fluids

Cited by 16 publications

References 7 publications

A model for establishing the ultimate enhancements (A∞) in the low to high magnetic field transfer dynamic nuclear polarization experiment

A model for establishing the ultimate enhancements (A∞) in the low to high magnetic field transfer dynamic nuclear polarization experiment

Dynamic nuclear polarization at high magnetic fields

NOE Enhancement in Continuous-Flow13C and15N FT NMR Using Upstream1H Preirradiation

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