High-Frequency Dynamic Nuclear Polarization in the Nuclear Rotating Frame

C. T. Farrar, D. A. Hall, G. J. Gerfen, M. Rosay, J. H. Ardenkjær-Larsen, R. G. Griffin

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

A proton dynamic nuclear polarization (DNP) NMR signal enhancement (e) close to thermal equilibrium, ∈ = 0.89, has been obtained at high field (B0 = 5 T, νepr = 139.5 GHz) using 15 mM trityl radical in a 40:60 water/glycerol frozen solution at 11 K. The electron-nuclear polarization transfer is performed in the nuclear rotating frame with microwave irradiation during a nuclear spin-lock pulse. The growth of the signal enhancement is governed by the rotating frame nuclear spin-lattice relaxation time (T1p), which is four orders of magnitude shorter than the nuclear spin-lattice relaxation time (T1n). Due to the rapid polarization transfer in the nuclear rotating frame the experiment can be recycled at a rate of 1/T1p and is not limited by the much slower lab frame nuclear spin-lattice relaxation rate (1/T1n). The increased repetition rate allowed in the nuclear rotating frame provides an effective enhancement per unit time1/2 of ∈t = 197. The nuclear rotating frame-DNP experiment does not require high microwave power; significant signal enhancements were obtained with a low-power (20 mW) Gunn diode microwave source and no microwave resonant structure. The symmetric trityl radical used as the polarization source is water-soluble and has a narrow EPR linewidth of 10 G at 139.5 GHz making it an ideal polarization source for high-field DNP/NMR studies of biological systems,

Original languageEnglish (US)
Pages (from-to)134-141
Number of pages8
JournalJournal of Magnetic Resonance
Volume144
Issue number1
DOIs
StatePublished - May 2000

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Nuclear and High Energy Physics
  • Condensed Matter Physics

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