Unassociated Molecular Chains in Physically Crosslinked Gellan Gels

It was demonstrated that gellan chains unassociated with the crosslinking domains in the gels are released from gellan gels into the external solution at 10 °C. The concentration of released gellan chains in the external solution was estimated using a phenol-sulfuric acid method. The release of gellan chains was suppressed with increasing concentration of potassium chloride or calcium chloride in the external solution whilst it was enhanced with increasing concentration of tetramethylammonium chloride in the external solution. It was suggested from differential scanning calorimetry that the released gellan chains adopt a double helix conformation at 10 °C. The experimental results indicated that the double helical gellan chains, which can be released from the gels, are unassociated with the crosslinking domains composed of the lateral association of double helices in gellan gels. In conclusion, it was shown that the amount of unassociated gellan chains contained in the physical gel can be determined by measuring the concentration of released gellan chains in the external solution.