title: Resolution and polarization distribution in cryogenic DNP/MAS experiments.
abstract: This contribution addresses four potential misconceptions associated with high-resolution dynamic nuclear polarization/magic angle spinning (DNP/MAS) experiments. First, spectral resolution is not generally compromised at the cryogenic temperatures at which DNP experiments are performed. As we demonstrate at a modest field of 9 T (380 MHz (1)H), 1 ppm linewidths are observed in DNP/MAS spectra of a membrane protein in its native lipid bilayer, and <0.4 ppm linewidths are reported in a crystalline peptide at 85 K. Second, we address the concerns about paramagnetic broadening in DNP/MAS spectra of proteins by demonstrating that the exogenous radical polarizing agents utilized for DNP are distributed in the sample in such a manner as to avoid paramagnetic broadening and thus maintain full spectral resolution. Third, the enhanced polarization is not localized around the polarizing agent, but rather is effectively and uniformly dispersed throughout the sample, even in the case of membrane proteins. Fourth, the distribution of polarization from the electron spins mediated via spin diffusion between (1)H-(1)H strongly dipolar coupled spins is so rapid that shorter magnetization recovery periods between signal averaging transients can be utilized in DNP/MAS experiments than in typical experiments performed at ambient temperature.
authors.affiliation: Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Alexander B
authors.initials: AB
authors.lastname: Barnes
authors.forename: Björn
authors.initials: B
authors.lastname: Corzilius
authors.forename: Melody L
authors.initials: ML
authors.lastname: Mak-Jurkauskas
authors.forename: Loren B
authors.initials: LB
authors.lastname: Andreas
authors.forename: Vikram S
authors.initials: VS
authors.lastname: Bajaj
authors.forename: Yoh
authors.initials: Y
authors.lastname: Matsuki
authors.forename: Marina L
authors.initials: ML
authors.lastname: Belenky
authors.forename: Johan
authors.initials: J
authors.lastname: Lugtenburg
authors.forename: Jagadishwar R
authors.initials: JR
authors.lastname: Sirigiri
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Temkin
authors.forename: Judith
authors.initials: J
authors.lastname: Herzfeld
authors.forename: Robert G
authors.initials: RG
authors.lastname: Griffin
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D008051:Lipid Bilayers / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010455:Peptides / Q000737:chemistry; D013696:Temperature
chemical_list: D008051:Lipid Bilayers; D008565:Membrane Proteins; D010455:Peptides
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