title: Solid-state dynamic nuclear polarization at 263 GHz: spectrometer design and experimental results.
abstract: Dynamic Nuclear Polarization (DNP) experiments transfer polarization from electron spins to nuclear spins with microwave irradiation of the electron spins for enhanced sensitivity in nuclear magnetic resonance (NMR) spectroscopy. Design and testing of a spectrometer for magic angle spinning (MAS) DNP experiments at 263 GHz microwave frequency, 400 MHz (1)H frequency is described. Microwaves are generated by a novel continuous-wave gyrotron, transmitted to the NMR probe via a transmission line, and irradiated on a 3.2 mm rotor for MAS DNP experiments. DNP signal enhancements of up to 80 have been measured at 95 K on urea and proline in water-glycerol with the biradical polarizing agent TOTAPOL. We characterize the experimental parameters affecting the DNP efficiency: the magnetic field dependence, temperature dependence and polarization build-up times, microwave power dependence, sample heating effects, and spinning frequency dependence of the DNP signal enhancement. Stable system operation, including DNP performance, is also demonstrated over a 36 h period.
authors.affiliation: Bruker BioSpin Corporation, 15 Fortune Drive, Billerica, MA 01821, USA. melanie.rosay@bruker-biospin.com
authors.forename: Melanie
authors.initials: M
authors.lastname: Rosay
authors.forename: Leo
authors.initials: L
authors.lastname: Tometich
authors.forename: Shane
authors.initials: S
authors.lastname: Pawsey
authors.forename: Reto
authors.initials: R
authors.lastname: Bader
authors.forename: Robert
authors.initials: R
authors.lastname: Schauwecker
authors.forename: Monica
authors.initials: M
authors.lastname: Blank
authors.forename: Philipp M
authors.initials: PM
authors.lastname: Borchard
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Cauffman
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Felch
authors.forename: Ralph T
authors.initials: RT
authors.lastname: Weber
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Temkin
authors.forename: Robert G
authors.initials: RG
authors.lastname: Griffin
authors.forename: Werner E
authors.initials: WE
authors.lastname: Maas
mesh_terms: D003497:Cyclic N-Oxides / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D008872:Microwaves; D011392:Proline / Q000737:chemistry; D020005:Propanols / Q000737:chemistry; D013696:Temperature; D014508:Urea / Q000737:chemistry
chemical_list: C521769:1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol; D003497:Cyclic N-Oxides; D020005:Propanols; D014508:Urea; D011392:Proline
references.citation: J Magn Reson. 2008 Dec;195(2):179-86
references.pmid: 18922715
references.citation: J Magn Reson. 2007 Dec;189(2):251-79
references.pmid: 17942352
references.citation: Appl Magn Reson. 2008 Aug;34(3-4):237-263
references.pmid: 19194532
references.citation: Proc Natl Acad Sci U S A. 2004 Jan 20;101(3):711-6
references.pmid: 14715898
references.citation: J Am Chem Soc. 2006 Sep 6;128(35):11385-90
references.pmid: 16939261
references.citation: J Magn Reson. 2000 Jan;142(1):97-101
references.pmid: 10617439
references.citation: J Am Chem Soc. 2006 Aug 23;128(33):10840-6
references.pmid: 16910679
references.citation: Proc Natl Acad Sci U S A. 2008 Jan 22;105(3):883-8
references.pmid: 18195364
references.citation: Nat Struct Biol. 1998 Jul;5 Suppl:508-12
references.pmid: 9665180
references.citation: J Magn Reson. 2009 Jun;198(2):261-70
references.pmid: 19356957
references.citation: IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc. 2006 Jun;34(3):518-523
references.pmid: 17431442
references.citation: Nat Struct Biol. 1995 Nov;2(11):990-8
references.pmid: 7583673
references.citation: J Am Chem Soc. 2002 Apr 3;124(13):3214-5
references.pmid: 11916398
references.citation: Phys Chem Chem Phys. 2010 Jun 14;12(22):5861-7
references.pmid: 20454732
references.citation: J Magn Reson. 1999 Sep;140(1):293-9
references.pmid: 10479576
references.citation: J Magn Reson. 2010 Jun;204(2):303-13
references.pmid: 20392658
references.citation: Proc Natl Acad Sci U S A. 2009 Jun 9;106(23):9244-9
references.pmid: 19474298
references.citation: J Chem Phys. 2008 Feb 7;128(5):052211
references.pmid: 18266416
references.citation: Science. 1997 May 9;276(5314):930-2
references.pmid: 9139651
references.citation: Phys Chem Chem Phys. 2010 Jun 14;12(22):5911-9
references.pmid: 20454733
references.citation: IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc. 2007 Jun;35(3):559-564
references.pmid: 19081779
references.citation: Curr Opin Struct Biol. 2004 Oct;14(5):554-61
references.pmid: 15465315
references.citation: IEEE Trans Microw Theory Tech. 2005 Jun;53(6 I):1863-1869
references.pmid: 17901907
references.citation: IEEE Trans Plasma Sci IEEE Nucl Plasma Sci Soc. 2006 Jun;34(3):524-533
references.pmid: 17710187
references.citation: Phys Rev Lett. 1993 Nov 22;71(21):3561-3564
references.pmid: 10055008
references.citation: J Magn Reson. 2003 Feb;160(2):85-90
references.pmid: 12615147
references.citation: J Magn Reson. 2009 Jan;196(1):84-7
references.pmid: 18930418
references.citation: J Chem Phys. 2008 Feb 7;128(5):052302
references.pmid: 18266419
references.citation: J Am Chem Soc. 2004 Sep 8;126(35):10844-5
references.pmid: 15339160
references.citation: J Am Chem Soc. 2001 Feb 7;123(5):1010-1
references.pmid: 11456650