title: Accurate measurement of heteronuclear dipolar couplings by phase-alternating R-symmetry (PARS) sequences in magic angle spinning NMR spectroscopy.
abstract: We report a Phase-Alternating R-Symmetry (PARS) dipolar recoupling scheme for accurate measurement of heteronuclear (1)H-X (X = (13)C, (15)N, (31)P, etc.) dipolar couplings in MAS NMR experiments. It is an improvement of conventional C- and R-symmetry type DIPSHIFT experiments where, in addition to the dipolar interaction, the (1)H CSA interaction persists and thereby introduces considerable errors in the dipolar measurements. In PARS, phase-shifted RN symmetry pulse blocks applied on the (1)H spins combined with π pulses applied on the X spins at the end of each RN block efficiently suppress the effect from (1)H chemical shift anisotropy, while keeping the (1)H-X dipolar couplings intact. Another advantage over conventional DIPSHIFT experiments, which require the signal to be detected in the form of a reduced-intensity Hahn echo, is that the series of π pulses refocuses the X chemical shift and avoids the necessity of echo formation. PARS permits determination of accurate dipolar couplings in a single experiment; it is suitable for a wide range of MAS conditions including both slow and fast MAS frequencies; and it assures dipolar truncation from the remote protons. The performance of PARS is tested on two model systems, [(15)N]-N-acetyl-valine and [U-(13)C,(15)N]-N-formyl-Met-Leu-Phe tripeptide. The application of PARS for site-resolved measurement of accurate (1)H-(15)N dipolar couplings in the context of 3D experiments is presented on U-(13)C,(15)N-enriched dynein light chain protein LC8.
authors.affiliation: Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Guangjin
authors.initials: G
authors.lastname: Hou
authors.affiliation: Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Xingyu
authors.initials: X
authors.lastname: Lu
authors.affiliation: Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Vega
authors.affiliation: Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, USA and Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, 1051 Biomedical Science Tower 3, 3501 Fifth Ave., Pittsburgh, Pennsylvania 15261, USA.
authors.forename: Tatyana
authors.initials: T
authors.lastname: Polenova
mesh_terms: D002247:Carbon Isotopes / Q000032:analysis; D009587:Nitrogen Isotopes / Q000032:analysis; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010759:Phosphorus Isotopes / Q000032:analysis; D011506:Proteins / Q000737:chemistry
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D010759:Phosphorus Isotopes; D011506:Proteins