title: High-resolution four-dimensional carbon-correlated 1H-1H ROESY experiments employing isotags and the filter diagonalization method for effective assignment of glycosidic linkages in oligosaccharides.
abstract: Four-dimensional nuclear magnetic resonance spectroscopy of oligosaccharides that correlates 1H-1H ROESY cross peaks to two additional 13C frequency dimensions is reported. The 13C frequencies were introduced by derivatization of all free hydroxyl groups with doubly 13C-labeled acetyl isotags. Pulse sequences were optimized for processing with the filter diagonalization method. The extensive overlap typically observed in 2D ROESY 1H-1H planes was alleviated by resolution of ROESY cross peaks in the two added dimensions associated with the carbon frequencies of the isotags. This enabled the interresidue 1H-1H ROESY cross peaks to be unambiguously assigned hence spatially proximate sugar spin systems across glycosidic bonds could be effectively ascertained. An experiment that selectively amplifies interresidue ROESY 1H-1H cross peaks is also reported. It moves the magnetization of an intraresidue proton normally correlated to a sugar H-1 signal orthogonally along the z axis prior to a Tr-ROESY mixing sequence. This virtually eliminates the incoherent intraresidue ROESY transfer, suppresses coherent TOCSY transfer, and markedly enhances the intensity of interresidue ROESY cross peaks.
authors.affiliation: Department of Cell and Developmental Biology and Biomolecular Structure Program, University of Colorado Health Sciences Center, Mail Stop 8108, P.O. Box 6511, Aurora, CO 80045, USA.
authors.forename: Geoffrey S
authors.initials: GS
authors.lastname: Armstrong
authors.forename: Brad
authors.initials: B
authors.lastname: Bendiak
mesh_terms: D002247:Carbon Isotopes; D005936:Glucans / Q000737:chemistry*; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D009844:Oligosaccharides / Q000737:chemistry*; D012815:Signal Processing, Computer-Assisted
chemical_list: D002247:Carbon Isotopes; D005936:Glucans; D009844:Oligosaccharides; C001290:glucan nigeran