The Complex Carbohydrate Research Center (CCRC)
Dept. of Biochemistry and Molecular Biology
The University of Georgia, Athens GA
Proton NMR Spectra of Xyloglucans
This Data Base consists of a searchable table of the 1H-NMR chemical shifts of xyloglucan oligoglycosyl alditols. Oligosaccharide subunits of xyloglucans were generated by endoglucanase treatment of the polymer and reduced with sodium borohydride. Borohydride treatment simplifies the purification and spectroscopic analysis of each xyloglucan oligosaccharide by transforming the interconverting anomeric forms of the reducing residues into a single, stable moiety (an alditol.) The 1H-NMR chemical shifts of the resulting oligoglycosyl alditols are similar, but not identical to those of the parent reducing oligosaccharides.
Xyloglucans are highly branched polymers with a cellulosic backbone (i.e., consisting of β-(1,4)-linked D-glucosyl residues). Many of the backbone residues bear glycosyl side chains, most often at C-6. If each glucosyl residue in the backbone, along with all of its pendant side chains, is considered as a substructure of the polymer, then the polymer can be considered as a linear array of these substructures. This is the basis for the most commonly used nomenclature used to specify xyloglucan structures.
The anomeric proton resonances of xyloglucan oligoglycosyl alditols are resolved from the other resonances, making them especially useful for rapid structural determination by NMR. The chemical shifts of these anomeric resonances are, to a first approximation, a function of a few, well-defined parameters:
The identity of the sugar residue, including its anomeric configuration and linkage;
The identity of the substructure containing the sugar residue.
The environment of the substructure containing the sugar residue. This includes end effects arising from the proximity of the side chain to the non-reducing or alditol end of the oligomer and the presence of other side chains in the immediate vicinity.
GC-EIMS of Partially Methylated Alditol Acetates
The Complex Carbohydrate Research Center (复杂碳水化合物研究中心)
Summary by 李晓霞 on 2002-11-27
Last updated by 李晓霞 on 2002-11-27