羊毛ケラチンタンバク誘導体への二価重金属イオンの結合機構

抄録

A gel chromatographic investigation has been made for the binding of Cu²⁺, Pb²⁺. Zn²⁺ and Cd²⁺ to soluble derivatives of high sulfur component of wool, namely, S-carboxylkeratin (K-COOH), S-β-aminoethylkeratin (K-NH₂) and keratose (K-SO₃H). A Sephadex G-25 gel column was used with 0.05 M acetate buffer in a pH range of 4.5-6.5 as eluent. The binding parameters and the numbers of the binding sites for the complex formation were evaluated by a procedure described by Klotz et al. The selectivity of the binding sites was examined by competitive binding experiments carried out for binary mixtures of the metal ions. The results indicate that (i) the binding parameters depend strongly on the type of the keratin derivatives; (ii) the carboxyl groups introduced act as binding sites for the divalent metal ions; (iii) the amino groups do not act as binding sites for Pb²⁺, Zn²⁺ and Cd²⁺ but act as strong binding sites for Cu²⁺ (iv) the binding data for Pb²⁺, Zn²⁺ and Cd²⁺ are analysed in terms of a single kind of binding sites for respective cations, while those for Cu²⁺ are analysed in terms of two kinds of independent binding sites with high and low binding constants; and (v) competition between Cu²⁺and Pb²⁺ takes place for the low affinity sites but not for the high affinity sites.