Dissolution DNP-NMR spectroscopy using galvinoxyl as a polarizing agent

Lloyd L. Lumata, Matthew E. Merritt, Craig R. Malloy, A. Dean Sherry, Johan Van Tol, Likai Song, Zoltan Kovacs

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

The goal of this work was to test feasibility of using galvinoxyl (2,6-di-tert-butyl-α-(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-1-ylidene) -p-tolyloxy) as a polarizing agent for dissolution dynamic nuclear polarization (DNP) NMR spectroscopy. We have found that galvinoxyl is reasonably soluble in ethyl acetate, chloroform, or acetone and the solutions formed good glasses when mixed together or with other solvents such as dimethyl sulfoxide. W-band electron spin resonance (ESR) measurements revealed that galvinoxyl has an ESR linewidth D intermediate between that of carbon-centered free radical trityl OX063 and the nitroxide-based 4-oxo-TEMPO, thus the DNP with galvinoxyl for nuclei with low gyromagnetic ratio γ such as 13C and 15N is expected to proceed predominantly via the thermal mixing process. The optimum radical concentration that would afford the highest 13C nuclear polarization (approximately 6% for [1- 13C]ethyl acetate) at 3.35 T and 1.4 K was found to be around 40 mM. After dissolution, large liquid-state NMR enhancements were achieved for a number of 13C and 15N compounds with long spin-lattice relaxation time T1. In addition, the hydrophobic galvinoxyl free radical can be easily filtered out from the dissolution liquid when water is used as the solvent. These results indicate that galvinoxyl can be considered as an easily available free radical polarizing agent for routine dissolution DNP-NMR spectroscopy.

Original languageEnglish (US)
Pages (from-to)14-19
Number of pages6
JournalJournal of Magnetic Resonance
Volume227
DOIs
StatePublished - Feb 2013

Keywords

  • Dynamic nuclear polarization
  • Free radical
  • Hyperpolarization
  • NMR
  • Thermal mixing

ASJC Scopus subject areas

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

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