On the structure of κ/ι-hybrid carrageenans Original Research Article

The coil-to-helix transition and temperature dependence of the viscosity of commercial κ/ι-hybrid carrageenans produced by the red algae Sarcothalia crispata, Mazaella laminarioides, and Chondrus crispus were studied using rheometry and optical rotation. The structure of these κ/ι-hybrid carrageenans was determined by 1H and 13C NMR spectroscopy combined with monosaccharide composition analysis. The coil-to-helix transitions, measured by polarimetry and rheometry, of the κ/ι-hybrid carrageenans are significantly different from those of pure κ- and ι-carrageenan, and from hand-made mixtures thereof. This provides evidence that the κ/ι-hybrid carrageenans are mixed chains, containing both κ- and ι-repeating units.