Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5406752 | Journal of Magnetic Resonance | 2010 | 7 Pages |
Abstract
Dynamic nuclear polarization (DNP) is an NMR-based technique which enables detection and spectral characterization of endogenous and exogenous paramagnetic substances measured via transfer of polarization from the saturated unpaired electron spin system to the NMR active nuclei. A variable field system capable of performing DNP spectroscopy with NMR detection at any magnetic field in the range 0-0.38Â T is described. The system is built around a clinical open-MRI system. To obtain EPR spectra via DNP, partial cancellation of the detection field B0NMR is required to alter the evolution field B0EPR at which the EPR excitation is achieved. The addition of resistive actively shielded field cancellation coils in the gap of the primary magnet provides this field offset in the range of 0-100Â mT. A description of the primary magnet, cancellation coils, power supplies, interfacing hardware, RF electronics and console are included. Performance of the instrument has been evaluated by acquiring DNP spectra of phantoms with aqueous nitroxide solutions (TEMPOL) at three NMR detection fields of 97Â G, 200Â G and 587Â G corresponding to 413Â kHz, 851.6Â kHz and 2.5Â MHz respectively and fixed EPR evolution field of 100Â G corresponding to an irradiation frequency of 282.3Â MHz. This variable-field DNP system offers great flexibility for the performance of DNP spectroscopy with independent optimum choice of EPR excitation and NMR detection fields.
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Authors
Keerthi Shet, George L. Caia, Eric Kesselring, Alexandre Samouilov, Sergey Petryakov, David J. Lurie, Jay L. Zweier,