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Updated: Apr 3, 2026
Controlling the Size, Shape and Stability of Supramolecular Polymers in Water
Published on: August 2, 2012
Magnetic Control of Macromolecular Conformations in Supramolecular Anionic Polysaccharide-Iron Complexes
Larissa Schefer1, Ariane Bulant1, Christophe Zeder1
1Department of Health Sciences & Technology, ETH Zürich, Schmelzbergstrasse 9, LFO E23, 8092 Zürich (Switzerland).
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.
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