title: NMR characterization of chemically synthesized branched α-dextrin model compounds.
abstract: 1H and 13C NMR chemical shifts were accurately determined by consistent referencing for an extensive set of chemically synthesized branched α-glucan model compounds. The model compounds include anomerically fixed and reducing oligosaccharides ranging in size from isomaltose to a doubly branched decasaccharide. Both the 13C1 chemical shift and the 13C6 chemical shifts in α-(1→6) glycosidic bonds are strongly dependent on the chemical structure in the vicinity of the branch point, especially on the addition of glucopyranosyl units towards the non-reducing end of the backbone chain. The conformational sampling at the branch point of the branched α-glucan model compounds was experimentally probed with homo-nuclear scalar couplings. Substitution at O6 consistently increases the fraction of C6-O6 trans conformations, but to a lesser extent, if the attachment occurs at the reducing end residue. Increasingly complex structures in the vicinity of the branch point increase the population of the gauche-trans conformation of the C5-C6 bond. This population change is found to correlate with the 13C6 chemical shift.
authors: Carlsberg Laboratory, Gamle Carlsberg Vej 10, 1799 Copenhagen V, Denmark.
authors: Bent O
authors: BO
authors: Petersen
authors: Plant Biochemistry Laboratory, Department of Plant Biology and Biotechnology, University of Copenhagen, 40 Thorvaldsensvej, DK 1871 Frederiksberg C, Copenhagen, Denmark; VILLUM Research Center 'Plant Plasticity', University of Copenhagen, 40 Thorvaldsensvej, DK 1871 Frederiksberg C, Copenhagen, Denmark.
authors: Mohammed Saddik
authors: MS
authors: Motawie
authors: Carlsberg Laboratory, Gamle Carlsberg Vej 10, 1799 Copenhagen V, Denmark; Plant Biochemistry Laboratory, Department of Plant Biology and Biotechnology, University of Copenhagen, 40 Thorvaldsensvej, DK 1871 Frederiksberg C, Copenhagen, Denmark; VILLUM Research Center 'Plant Plasticity', University of Copenhagen, 40 Thorvaldsensvej, DK 1871 Frederiksberg C, Copenhagen, Denmark.
authors: Birger Lindberg
authors: BL
authors: Møller
authors: Carlsberg Laboratory, Gamle Carlsberg Vej 10, 1799 Copenhagen V, Denmark.
authors: Ole
authors: O
authors: Hindsgaul
authors: Carlsberg Laboratory, Gamle Carlsberg Vej 10, 1799 Copenhagen V, Denmark. Electronic address: semei@kemi.dtu.dk.
authors: Sebastian
authors: S
authors: Meier
mesh_terms: D002236:Carbohydrate Conformation; D009682:Magnetic Resonance Spectroscopy; D058105:Polymerization; D047391:alpha-Cyclodextrins / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D047391:alpha-Cyclodextrins; C032613:alpha-cyclodextrin
keywords: Amylopectin; Carbohydrate NMR; Carbohydrate mixtures; Limit dextrin; Starch