Hydration—dehydration-induced conformational changes of agarose, and kappa- and iota-carrageenans as studied by high-resolution solid-state 13C-nuclear magnetic resonance spectroscopy

Abstract High-resolution, solid-state 13 C-n.m.r. spectra of agarose, and kappa- and iota-carrageenans were recorded for various states, including anhydrous and hydrated powder, film, gel, and lyophilized gel. The 13 C-n.m.r. spectra varied substantially with the extent of hydration. Fully hydrated samples, as in the agarose gels, gave rise to 13 C-n.m.r. peaks of the narrowest line widths, whereas dehydration caused considerable line-broadening or displacement of the G1 peak (or both). These observations were interpreted in terms of hydration-dehydration-induced conformational alteration or readjustment, depending on the extent of hydration or dehydration and the variety of samples used. 13 C-n.m.r. spectrometry of agarose gel by solid-state n.m.r. technique also indicated the existence of a rather rigid network structure with an anisotropic molecular tumbling.