Polyelectrolytic aspects of the thermodynamics of conformational transition: kappa-Carrageenan in formamide

A recently published method for the determination of the enthalpy and entro py changes of nonionic origin upon conformational transition of linear biop olyelectrolytes in solution [J. C. Benegas, A. Cesaro, R. Rizzo and S. Paol etti (1998) Biopolymers, Vol. 45, pp. 203-216] has been extended from the c ase of aqueous salt solutions to that of the organic solvent formamide (FA) . The calculation have been applied to the case of the intramolecular trans ition of the K+ salt form of the sulfated polysaccharide kappa-carrageenan. The method proved to be effective in providing the desired data in FA, as it has been previously been successful for the water cases. The comparison between the predicted enthalpy change of transition and the microcalorimetr ic experimental one turned out to be excellent, thereby ensuring on the val idity of the approach. (C) 1999 John Wiley & Sons, Inc.