CIRCULAR-DICHROISM STUDY ON POLYELECTROLYTIC PROPERTIES OF CARBOXYMETHYLDEXTRAN

The effects of neutralization, charge density, concentration, counterion, and added salts on CD spectra of carboxymethyldextran (Cm‐dextran) were systematically investigated in order to understand the polyelectrolytic effects of ionic polysaccharides on CD spectra. CD curves of sodium Cm‐dextran showed a negative band near 214 nm due to the carboxyl n – π* transition, but the acid spectrum indicated an additional positive band near 225–228 nm, depending on the charge density. The increase in charge density caused the increase in the magnitude of ellipticity and the red shift of the band. The magnitude of the CD band showed a remarkable concentration dependence in water without any change of position and shape but was independent of concentration in the presence of salt. CD spectra of Cm‐dextran were drastically influenced by the kind of counterion and added salts. These variations of CD spectra under different conditions are discussed from the viewpoint of ion binding and the intermolecular and intramolecular electrostatic interactions of this polysaccharide. Copyright © 1979 John Wiley & Sons, Inc.