コンドロイチン硫酸に対するカルシウムイオンとナトリウムイオンの結合

概要

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The amounts of both Ca^<2+> and Na^+, x and y, respectively, bound to C-type chondroitin sulfate (Chs) from an aqueous solution of CaCl_2 mixed with NaCl were obtained by the membrane equilibrium method. To estimate x and y under the effect of the Donnan equilibrium, [Ca^<2+>] and [Cl^-] for both sides of the dialysing tube and [Chs] for the inner side were analysed. The binding isotherm for Ca^<2+> was of the Langmuir type, and both x and k_<C_a>^<2+>, the binding constant for Ca^<2+>, decreased with ionic strength, J. On the other hand, the binding isotherm for Na^+ was not of the Langmuir type but its shape was explained as the competitive adsorption of the two components, Na^+ and Ca^<2+>, because Ca^<2+> binds more strongly to Chs than Na^+ and, therefore, the effect of coexistence of Ca^<2+> with Na^+ cannot be neglected when the Na^+ binding is examined. It was also suggested that y and k_<Na^+> decreases with J when the amount of the occupied site by the Ca^<2+> is kept constant at x. The degree of the ionization, z, of Chs was found to be 0.40-0.41 for Na_2Chs and 0.20-0.21 for CaChs by this membrane equilibrium method assuming x+y+z=1. These values coincide with those obtained from the vapour pressure osmometry by the authors and with the literature values calculated with considering the Manning theory.
公益社団法人日本薬学会の論文
1979-06-25