CHELATING ABILITY AND ENZYMATIC-HYDROLYSIS OF WATER-SOLUBLE CHITOSANS

A novel water-soluble chitosan (NHMF-chitosan) was synthesized from crab chitosan and 5-hydroxymethyl-2-furfural, an amply available derivative of sucrose. Thc chelating ability of NHMF-chitosan and N-carboxybutyl chitosan in dilute aqueous solutions was studied by spectrophotometric and calorimetric methods. Both carbohydrate polymers were found to chelate Cu(II), the binding constants, K(B), being 9 X 10(4) 1.mol-1 for NHMF-chitosan and 2.2 X 10(3) for N-carboxybutyl chitosan, the latter was also able to chelate Pb(II), but no enthalpy variations were observed for other divalent cations. Chelation was strongly influenced by pH, and, to some extent, by temperature. Circular dichroism (cd) measurements revealed a positive rather than negative band at 225 nm, indicative of chirality change for NHMF-chitosan, which was found, however, to be a substrate for lysozyme.