SynopsisA structure determination of the naturally occrirring marine algal polysaccharide polyp-D-mannuronic acid is described. The structure consists of l e -+ 4e linked o-mannuronic acid chains with the monosaccharide units in the C1 chair conformation. The X-ray fiber diffraction photograph obtained from bundles of fibers prepared forom Fucus vesiculosus !as been in$exed to an orthorhombic unit cell in which a = 7.6 A, b (fiber axis) = 10.4 A, c = 8.6 A, the unit cell containing two disaccharide chain segments with space group P212121.A sheet-like structure involving one intra-chain, one intra-sheet, and one inter-sheet hydrogen bond per monosaccharide is proposed. Features of the chain-packing arrangement are compared with mannan.

synopsisA structural investigation of the marine algal polysaccharide poly-a-L-guluronic acid is described. The molecular chains consist. of 1 + 4 diaxially linked Irguluronic acid residues in the 1C chair conformation and are stabilized in a twofold helii conformation by an intra-molecular O(2)H. . . O(6)D hydrogen-bond. The X-ray fiber diffraction photograph has been indexed to an orthorhombic unit cell in which a = 8.6 & b (fiber axis) = 8.7 A, c = 10.7A.A structure corresponding to the space group P212121 is proposed, in which all intermolecular hydrogen bonds interact with water molecules and in which all oxygen atoms except for the inaccessible bridge oxygens are involved. The relationship between the shape and structure of the polyguluronic acid molecule and its biological function is discussed.

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