title: The efficiency of DPPH as a polarising agent for DNP-NMR spectroscopy.
abstract: The free radical 2,2-diphenyl-1-pycrylhydrazyl (DPPH) was tested as a polarising agent for fast dissolution dynamic nuclear polarisation (DNP) NMR spectroscopy. DPPH was found to be reasonably soluble in sulfolane and the optimum concentration for DNP is 20-40 mM depending upon whether short polarisation times or the maximum signal intensity is needed. W-band ESR measurements revealed that the ESR linewidth D of DPPH is intermediate between that of BDPA and 4-oxo-TEMPO. Several thousand-fold NMR signal enhancements in the liquid-state were achieved for (13)C, (15)N, (89)Y, and (109)Ag compounds, demonstrating that DPPH can be added to the list of polarising agents for DNP-NMR spectroscopy. Furthermore, the hydrophobic DPPH free radical can be easily filtered out from the dissolution liquid when water is used as the dissolution solvent.
authors.affiliation: Advanced Imaging Research Center, University of Texas, Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390 USA. ; Tel: +1-214-645-2750.
authors.forename: Lloyd
authors.initials: L
authors.lastname: Lumata
authors.forename: Matthew
authors.initials: M
authors.lastname: Merritt
authors.forename: Chalermchai
authors.initials: C
authors.lastname: Khemtong
authors.forename: S James
authors.initials: SJ
authors.lastname: Ratnakar
authors.forename: Johan
authors.initials: J
authors.lastname: van Tol
authors.forename: Lu
authors.initials: L
authors.lastname: Yu
authors.forename: Likai
authors.initials: L
authors.lastname: Song
authors.forename: Zoltan
authors.initials: Z
authors.lastname: Kovacs