A study of the helix–coil transition of ι-carrageenan segments by light scattering and membrane osmometry

Abstract

An ι-carrageenan has been selectively cleaved at the galactose 6-sulphate kink points to give short chain segments which do not gel but which give the optical rotation–temperature curve characteristic of gelation. This optical rotation change has previously been attributed to a helix to coil transition. The molecular weight changes with temperature of these ι-carrageenan segments have been measured by light scattering and osmometry and it has been found that the optical rotation shift is paralleled by a dimerisation thus confirming the hypothesis of a coil to double helix transition. Light scattering shows behaviour typical of concentration dependent aggregation in both states, but this is not detected by osmometry.