title: A novel variable field system for field-cycled dynamic nuclear polarization spectroscopy.
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 0-0.38 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 B(0)(NMR) is required to alter the evolution field B(0)(EPR) 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 0-100 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 97 G, 200 G and 587 G corresponding to 413 kHz, 851.6 kHz and 2.5 MHz respectively and fixed EPR evolution field of 100 G corresponding to an irradiation frequency of 282.3 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.
authors.affiliation: Davis Heart and Lung Research Institute and the Division of Cardiovascular Medicine, The Ohio State University, College of Medicine, Columbus, OH 43210, USA.
authors.forename: Keerthi
authors.initials: K
authors.lastname: Shet
authors.forename: George L
authors.initials: GL
authors.lastname: Caia
authors.forename: Eric
authors.initials: E
authors.lastname: Kesselring
authors.forename: Alexandre
authors.initials: A
authors.lastname: Samouilov
authors.forename: Sergey
authors.initials: S
authors.lastname: Petryakov
authors.forename: David J
authors.initials: DJ
authors.lastname: Lurie
authors.forename: Jay L
authors.initials: JL
authors.lastname: Zweier
mesh_terms: D003497:Cyclic N-Oxides / Q000737:chemistry; D004574:Electromagnetic Fields; D004578:Electron Spin Resonance Spectroscopy; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009569:Nitric Oxide / Q000737:chemistry; D013113:Spin Labels
chemical_list: D003497:Cyclic N-Oxides; D013113:Spin Labels; D009569:Nitric Oxide; C001803:tempol