BINDING OF ANIONS BY DENATURED PROTEINS

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Abstract
The adsorption by soluble and insoluble heat-denatured lysozyme of eight anionic dyes, including methyl orange, has been determined at several temperatures and pH values. In addition, the adsorption of methyl orange by both the soluble and insoluble forms of seven other heat-denatured proteins has been determined as a function of temperature and pH. The isotherms, which are normal, reproducible, reversible, and independent of protein concentration confirm the notion of a sheath of strongly orientated water molecules about small positive proteins. They also demonstrate directly the importance of −ΔF of hydration in protein interaction studies. pH dependence of adsorption of methyl orange and other anions to denatured proteins is normal but −ΔH of adsorption per mole of anion bound is greater than for the corresponding native form.These results discredit the current concept of unique specific binding sites on a protein for weak interactions of the type studied.