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Coil-helix transition of ι-carrageenan as a function of chain regularity

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Author: Velde, F. van de · Rollema, H.S. · Grinberg, N.V. · Burova, T.V. · Grinberg, V.Ya. · Hans Tromp, R.
Type:article
Date:2002
Institution: TNO Voeding
Source:Biopolymers, 4, 65, 299-312
Identifier: 236778
doi: doi:10.1002/bip.10250
Keywords: Health · Carrageenan · Coil-to-helix transition · Differential scanning calorimetry · NMR · Optical rotation · Polysaccharides · Rheometry · Structure analysis · Differential scanning calorimetry · Light scattering · Monomers · Optical rotation · Size exclusion chromatography · Rheological properties · Biopolymers · carrageenan · article · conformational transition · cross linking · differential scanning calorimetry · flow measurement · gel permeation chromatography · laser · light scattering · nonhuman · optical rotation · protein conformation · structure analysis · Carbohydrate Conformation · Carrageenan · Gels · Molecular Weight · Rheology · Thermodynamics · Eucheuma

Abstract

A series of ι-carrageenans containing different amounts of v-carrageenan (0-23 monomer %) have been prepared from neutrally extracted carrageenan of Eucheuma denticulatum. v-Carrageenan is the biochemical precursor of ι-carrageenan. The conformational order-disorder transition and rheological properties of these carrageenans were studied using optical rotation, rheometry, size exclusion chromatography coupled to multiangle laser light scattering, and high-sensitivity differential scanning calorimetry. The helix forming capacity of ι-carrageenan turns out to decrease monotonously with increasing amount of v-units. In contrast, the rheological properties of ι-carrageenan are remarkably enhanced by the presence of a small amount of v-units, yielding a maximum twofold increase in G′ at 3% v-units. It is concluded that the structure-forming capacity of ι-carrageenan, containing a small amount of v-carrageenan, is significantly higher than that of pure ι-carrageenan. This phenomenon is explained in terms of the balance between the helical content and the number of cross-links between chains, taking into consideration the fact that v-units introduce "kinks" in the chain conformation enabling neighboring chains to connect. Increasing amounts of v-units increase the number of cross-links in the network, resulting in increased gel strength. On the other hand, a reduced length of the helical strands weakens the cross-links between the different chains and, consequently, the gel. © 2002 Wiley Periodicals, Inc. Chemicals/CAS: Carrageenan, 9000-07-1; Gels