title: Probing heteronuclear (15)N-(17)O and (13)C-(17)O connectivities and proximities by solid-state NMR spectroscopy.
abstract: Heteronuclear solid-state magic-angle spinning (MAS) NMR experiments for probing (15)N-(17)O dipolar and J couplings are presented for [(2)H(NH(3)),1-(13)C,(15)N,(17)O(2)]glycine.(2)HCl and [(15)N(2),(17)O(2)]uracil. Two-dimensional (15)N-(17)O correlation spectra are obtained using the R(3)-HMQC experiment; for glycine.(2)HCl, the intensity of the resolved peaks for the CO and C-O(2)H (17)O resonances corresponds to the relative magnitude of the respective (15)N-(17)O dipolar couplings. (17)O-(15)N REDOR curves are presented for glycine.(2)HCl; fits of the initial buildup (DeltaS/S < 0.2) yield effective dipolar couplings in agreement with (+/-20%) the root-sum-squared dipolar couplings determined from the crystal structure. Experimental (15)N-(17)O REAPDOR curves for the (15)N resonances in glycine.(2)HCl and uracil fit well to the universal curve presented by Goldbourt et al. (J. Am. Chem. Soc. 2003, 125, 11194). Heteronuclear (13)C-(17)O and (15)N-(17)O J couplings were experimentally determined from fits of the quotient of the integrated intensity obtained in a heteronuclear and a homonuclear spin-echo experiment, S(Q)(tau) = S(HET)(tau)/S(HOM)(tau). For glycine.(2)HCl, (1)J(CO) was determined as 24.7 +/- 0.2 and 25.3 +/- 0.3 Hz for the CO and C-O(2)H resonances, respectively, while for uracil, the average of the two NH...O hydrogen-bond-mediated J couplings was determined as 5.1 +/- 0.6 Hz. In addition, two-bond intramolecular J couplings, (2)J(OO) = 8.8 +/- 0.9 Hz and (2)J(N1,N3) = 2.7 +/- 0.1 Hz, were determined for glycine.(2)HCl and uracil, respectively. Excellent agreement was found with J couplings calculated using the CASTEP code using geometrically optimized crystal structures for glycine.HCl [(1)J(CO)(CO) = 24.9 Hz, (1)J(CO)(COH) = 27.5 Hz, (2)J(OO) = 7.9 Hz] and uracil [(2h)J(N1,O4) = 6.1 Hz, (2h)J(N3,O4) = 4.6 Hz, (2)J(N1,N3) = 2.7 Hz].
authors.affiliation: Department of Physics, University of Warwick, Coventry, UK.
authors.forename: Ivan
authors.initials: I
authors.lastname: Hung
authors.forename: Anne-Christine
authors.initials: AC
authors.lastname: Uldry
authors.forename: Johanna
authors.initials: J
authors.lastname: Becker-Baldus
authors.forename: Amy L
authors.initials: AL
authors.lastname: Webber
authors.forename: Alan
authors.initials: A
authors.lastname: Wong
authors.forename: Mark E
authors.initials: ME
authors.lastname: Smith
authors.forename: Siân A
authors.initials: SA
authors.lastname: Joyce
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Yates
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Pickard
authors.forename: Ray
authors.initials: R
authors.lastname: Dupree
authors.forename: Steven P
authors.initials: SP
authors.lastname: Brown
mesh_terms: D002247:Carbon Isotopes; D005998:Glycine / Q000737:chemistry*; D006860:Hydrogen Bonding; D007553:Isotope Labeling; D008958:Models, Molecular; D009587:Nitrogen Isotopes; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D010103:Oxygen Isotopes; D014498:Uracil / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D010103:Oxygen Isotopes; D014498:Uracil; D005998:Glycine