title: Unravelling secondary structure changes on individual anionic polysaccharide chains by atomic force microscopy.
abstract: The structural conformations of the anionic carrageenan polysaccharides in the presence of monovalent salt close to physiological conditions are studied by atomic force microscopy. Iota-carrageenan undergoes a coil-helix transition at high ionic strength, whereas lambda-carrageenan remains in the coiled state. Polymer statistical analysis reveals an increase in persistence length from 22.6±0.2 nm in the random coil, to 26.4±0.2 nm in the ordered helical conformation, indicating an increased rigidity of the helical iota-carrageenan chains. The many decades-long debated issue on whether the ordered state can exist as single or double helix, is conclusively resolved by demonstrating the existence of a unimeric helix formed intramolecularly by a single polymer chain.
authors.affiliation: Food & Soft Materials Science, Institute of Food, Nutrition & Health, Department of Health Sciences & Technology, ETH Zürich, Schmelzbergstraße 9, LFO E23, 8092 Zürich (Switzerland) http://www.ifnh.ethz.ch/lwm.
authors.forename: Larissa
authors.initials: L
authors.lastname: Schefer
authors.forename: Jozef
authors.initials: J
authors.lastname: Adamcik
authors.forename: Raffaele
authors.initials: R
authors.lastname: Mezzenga
mesh_terms: D000838:Anions / Q000737:chemistry; D002351:Carrageenan / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008968:Molecular Conformation; D009994:Osmolar Concentration; D011108:Polymers / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry*
chemical_list: D000838:Anions; D011108:Polymers; D011134:Polysaccharides; D002351:Carrageenan; D004247:DNA
keywords: atomic force microscopy; carbohydrates; coil-helix transition; conformation analysis; polymer physics