title: Magnetic Control of Macromolecular Conformations in Supramolecular Anionic Polysaccharide-Iron Complexes.
abstract: The anionic iota carrageenan polysaccharide is enriched with Fe(II) and Fe(III) by ion exchange against FeSO4 and FeCl3 . With divalent iron, portions of polymer chains undergo a secondary structure transition from random coils to single helices. The single-chain macromolecular conformations can be manipulated by an external magnetic field: upon exposure to 1.1 T, the helical portions exhibit 1.5-fold stiffening and 1.1-fold stretching, whereas the coil conformations respond much less as a result of lower contents of condensed iron ions. Along with the coil-helix transition, the trivalent iron triggers the formation of superstructures. The applicability of iron-enriched iota carrageenan as functional ingredient for food fortification is tested by free Fe(2+) and Fe(3+) contents, respectively, with the most promising iota-Fe(III) yielding 53% of bound iron, which is due to the superstructures, where the ferric ions are chelated by the supramolecularly self-assembled polymer host.
authors.affiliation: Department of Health Sciences & Technology, ETH Zürich, Schmelzbergstrasse 9, LFO E23, 8092 Zürich (Switzerland).
authors.forename: Larissa
authors.initials: L
authors.lastname: Schefer
authors.affiliation: Department of Health Sciences & Technology, ETH Zürich, Schmelzbergstrasse 9, LFO E23, 8092 Zürich (Switzerland).
authors.forename: Ariane
authors.initials: A
authors.lastname: Bulant
authors.affiliation: Department of Health Sciences & Technology, ETH Zürich, Schmelzbergstrasse 9, LFO E23, 8092 Zürich (Switzerland).
authors.forename: Christophe
authors.initials: C
authors.lastname: Zeder
authors.affiliation: Department of Health Sciences & Technology, ETH Zürich, Schmelzbergstrasse 9, LFO E23, 8092 Zürich (Switzerland).
authors.forename: Abhijit
authors.initials: A
authors.lastname: Saha
authors.affiliation: Department of Health Sciences & Technology, ETH Zürich, Schmelzbergstrasse 9, LFO E23, 8092 Zürich (Switzerland). raffaele.mezzenga@hest.ethz.ch.
authors.forename: Raffaele
authors.initials: R
authors.lastname: Mezzenga
mesh_terms: D000838:Anions / Q000737:chemistry; D058085:Iron Compounds / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D060526:Magnetic Fields; D018625:Microscopy, Atomic Force; D008968:Molecular Conformation; D010316:Particle Size; D011134:Polysaccharides / Q000737:chemistry*
chemical_list: D000838:Anions; D058085:Iron Compounds; D046911:Macromolecular Substances; D011134:Polysaccharides
keywords: atomic force microscopy; carbohydrates; coil-helix transition; conformation analysis; magnetic manipulation