THERMODYNAMICS OF POLYSACCHARIDE POLYELECTROLYTES - ENTHALPY CHANGES IN THE CONFORMATIONAL TRANSITION OF KAPPA-CARRAGEENAN

An approach, based entirely on Counterion Condensation (CC) polyelectrolyte theory and on thermodynamic consideration, is used to derive the ionic and the non-ionic energy contributions for processes involving the conformational transition of a linear polyelectrolyte. As an example of application, the conformational transition of the algal polysaccharide, kappa-carrageenan is analysed. This anionic polymer undergoes a thermoreversible disorder-order conformational transition which parallels specific binding of cations (as K+, Cs+,...) and, quite unusually, of the iodide anion. Experimental data on the conformational process and on the binding process will be compared with the theoretical prediction.