title: Three-dimensional structure of the sodium salt of iota-carrageenan.
abstract: The three-dimensional structure of the sodium salt of iota-carrageenan has been determined by using X-ray diffraction data collected from its polycrystalline and oriented fibers. The molecule forms a half-staggered, parallel, threefold, right-handed double helix that is stabilized by interchain hydrogen bonds from 2- and 6-hydroxyl groups in the galactosyl units. Three helices are organized in a trigonal unit cell, of dimensions a=24.02 and c=12.93 A, with a lateral separation of 13.9 A for each pair. Both 2- and 4-sulfate groups are essential in helix-helix interactions that are mediated only by sodium ions and water molecules.
authors.affiliation: Whistler Center for Carbohydrate Research, Food Science Building, Purdue University, West Lafayette, IN 47907-1160, USA.
authors.forename: S
authors.initials: S
authors.lastname: Janaswamy
authors.forename: R
authors.initials: R
authors.lastname: Chandrasekaran
mesh_terms: D002351:Carrageenan / Q000737:chemistry*; D005690:Galactose / Q000737:chemistry*; D006860:Hydrogen Bonding; D021621:Imaging, Three-Dimensional / Q000379:methods; D007477:Ions / Q000737:chemistry; D008958:Models, Molecular; D011134:Polysaccharides / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry*; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction / Q000379:methods
chemical_list: D007477:Ions; D011134:Polysaccharides; D014867:Water; D002351:Carrageenan; D012964:Sodium; D005690:Galactose