Salt effects on multiple-point adsorption of target molecules by heteropolymer gel

The effect of salt concentration on the affinity of a thermosensitive heter opolymer gel for various multiple-point adsorbing target molecules was exam ined. The gel has positively charged adsorber monomers which can interact e lectrostatically with negatively charged groups on the target molecules. Ad sorption of the targets was found to depend strongly on the salt concentrat ion. The adsorption affinity decreased by several orders of magnitude with a slight increase of the salt concentration, showing that, quite unlike the trivial Donnan potential effect, the negative ions of the salt compete wit h target molecules for the adsorption sites. We have found the power law re lationship between the affinity for the target and the concentration of the coexistent salt for gels in the collapsed state. (C) 2001 American Institu te of Physics.