Immobilized-metal affinity chromatography of serum proteins on gel-immobilized group III A metal ions

A chromatographic adsorbent (TED-Sepharose) capable of chelating various di- and trivalent metal ions was prepared by introducing tris(carboxymethyl)ethylenediamine into agarose. This gel was charged with Al3+, Ga3+, In3+, and Tl3+ to form immobilized-metal affinity adsorbents, and their adsorption behavior toward serum proteins at various pH values was studied. At low pH, these adsorbents behave as ion exchangers. At pH 7 and above, their adsorption behavior shows a high degree of selectivity but with varying affinity profiles for serum proteins. The adsorbents based on Al3+ and Ga3+ thus have negligible affinity for proteins at pH 7.6, whereas that based on In3+ exhibits a low but significantly higher affinity for proteins compared to the previous two. On the other hand, the Tl3+-based adsorbent showed a much higher capacity to adsorb serum proteins. Selective fractionation by affinity elution of human serum proteins adsorbed to an immobilized Tl3+ is also presented.