Mariko Kakuta

Chain Conformation of a Glucurono-xylo-mannan Isolated from Fruit Body of Tremella fuciformis Berk

Abstract A possible chain conformation of the acidic heteropolysaccharide isolated from the fruit body of Tremella fuciformis Berk (Shirokikurage) was proposed by the X-ray diffraction study combined with the computational model building technique. The polysaccharide consists of a linear backbone of 1,3-linked α-D-mannose which is highly substituted with β-D-xylose, β-D-glucuronic acid, and 1,2-linked β-D-xylobiose units at the C2 position of the mannose residue. It was suggested from the X-ray data, together with the knowledge of the chain conformations proposed for other 1,3-linked α-D-glycans, that the backbone conformation has the left-handed, three-fold helical symmetry. Orientations of the side group residues on the mannan backbone were suggested from the theoretical calculations. The proposed conformation of a repeating unit of the helical model consisted of six mannose residues and three side group residues in the 2.42 nm distance along the fiber axis. Two interresidue hydrogen bonds were observed...

X-ray study of beijeran sodium salts, a new galacturonic acid-containing exo-polysaccharide.

X-Ray fiber diffraction patterns were obtained from oriented films of sodium salts of a new uronic acid-containing polysaccharide (beijeran) both in its native, poly [-->3)-alpha-D-GalA-(1-->3)-beta-L-Rha-(1-->3)-alpha-D-Glc-O6Ac-(1 -->], and deacetylated forms. Initially the stretched films of both polysaccharides were amorphous, but the crystallinity was much improved by annealing at high temperature. The deacetylated specimen had higher crystallinity than the native. Both films showed similar X-ray fiber patterns indicating that these polysaccharides had similar unit cell dimensions and that the O-acetyl groups in the native beijeran chain did not disturb the regular array in the crystal having space group P21. All the visible reflections could be indexed in terms of a monoclinic unit cell with dimensions a = 1.277, b = 1.611, c (fiber axis) = 2.437 nm, and gamma = 96.79 degrees. The fiber axis length and the presence of (002) and (006) reflections indicated that the conformation was made up of two trisaccharide residues, in an extended two-fold helix.