Structural components of alginic acid. I. The crystalline structure of poly‐β‐<scp>D</scp>‐mannuronic acid. Results of X‐ray diffraction and polarized infrared studies

Abstract

Abstract A Structure determination of the naturally occuring marine algal polysaccharide poly‐β‐ D ‐mannuronic acid is described. The structure consists of 1e → 4e linked D ‐mannuronic acid chains with the monosaccharide units in the C1 chair conformation. The X‐ray fiber diffraction photograph obtained from bundles of fibers prepared from Fucus vesiculosus has been indexed to an orthorhombic unit cell in which a =7.6 Å, b (fiber axis) = 10.4 Å, c = 8.6 Å, the unit cell containing two disaccharide chain segments with space group P2 1 2 1 2 1 . 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.