Residual 2H quadrupolar couplings in weakly aligned carbohydrates.
We report a novel two-dimensional NMR pulse scheme for the 1H-detected observation of 2H in isotopically 13C, 2H-enriched carbohydrates. This scheme is used for the indirect observation of residual quadrupolar couplings in 13C, 2H-enriched methyl-beta-D-glucopyranoside weakly aligned in a dilute lyotropic liquid-crystalline medium comprising 20% (w/v) dihexanoyl-phosphatidylcholine/dimyristoyl-phosphatidylcholine (1:3 mol/mol) in D2O. The observed residual quadrupolar couplings are substantially larger than residual dipolar one-bond 13C-1H couplings under the same experimental conditions. These quadrupolar couplings are thus a useful alternative to dipolar couplings for the structural analysis of small molecules that align very weakly in dilute liquid-crystalline media. Moreover, since the quadrupolar coupling constant is very uniform throughout endocyclic deuterons of the carbohydrate, these data suggest that adoption of a single average value of this parameter in 2H relaxation studies on the glycan moieties of glycoproteins and glycopeptides is a valid assumption.
Kjellberg
A
A
School of Biochemistry and Molecular Biology, University of Leeds, Leeds, LS2 9JT, United Kingdom.
Homans
S W
SW
D000465:Algorithms; D002241:Carbohydrates / Q000737:chemistry*; D002247:Carbon Isotopes; D003903:Deuterium; D009682:Magnetic Resonance Spectroscopy
D002241:Carbohydrates; D002247:Carbon Isotopes; D003903:Deuterium