Helix-coil transition in gelling polysaccharides

Abstract

The coil/helix transition in solutions of a degraded i-carrageenan in 0.1 M NaCl has been studied using optical rotation methods and differential scanning calorimetry. Provided the molecular weight distribution profile is included in the model, a simple two-state all-or-none mechanism is an adequate. description of the transition process. The enthalpy and entropy changes which accompany the transfer of a disaccharide residue from the double helical conformation to the coil conformation are, based on the two-state all-or-none model, ΔH^°_r= 1.2 kcal (mol of residue)^–1 and ΔS^°_r= 3.55 cal (mol of residue)^–1 K^–1.