The adsorption of transition metal, lanthanide, and actinide ions to ovotransferrin (conalbumin) immobilized to sepharose (via the cyanogen bromide method) has been examined. Adsorption of ions as a function of time and adsorption isotherms at pH 8 have been determined and analyzed using the Freundlich model. Distribution coefficients between the pH values 2 and 9 have been measured. The results indicate that immobilization of the protein has little effect on its interactions with metal ions compared with the protein in solution, an important prerequisite for use of this matrix in metalloprotein affinity metal chromatography (MAMC).Key words: transferrin, conalbumin, adsorption isotherms.
NOTATION
C,,Metal ion concentration in solution at equilibrium (mg dm-3) EDTA Ethylenediaminetetraacetate Hepes 4-(2-hydroxyethyl)-1-piperazine-2-ethanesulfonic-Metal ion quantity adsorbed on matrix qeq Metal ion quantity adsorbed on maxtrix at equilibrium (mg g-')(mg g-l )methodology depends on the cost and robustness of the support and the p r~t e i n ,~ as well as the cost of the reagents and methods utilized to achieve a functional metal affinity column. In order to optimize the cost of operation, a detailed knowledge of the conditions associated with metal binding and release is required. If metal ion-binding to the supported protein reaches equilibrium rapidly, as is observed for the free protein," then this equilibrium can be represented by the Freundlich adsorption i~o t h e r m ,~ which in its linearized form given below allows for detailed comparison of the capacity ( K , ) and intensity (n) of metal ion binding under a variety of conditions.