Adsorption and selectivity characteristics of several human serum proteinswith immobilised hard Lewis metal ion-chelate adsorbents

In this investigation, human serum has been used as an example of a crude p rotein mixture to define the protein binding characteristics and selectivit y of several immobilised hard Lewis metal ion affinity chromatographic (IMA C) adsorbents. Specifically, the binding properties of immobilised O-phosph aserine (im-OPS) and g-hydroxyquinoline (im-8-HQ), with immobilised iminodi acetic acid as a control system, have been investigated in combination with the hard Lewis metal ions, Al3+, Ca2+, Fe3+,Yb3+, and the borderline metal ion, Cu2+, over the pH range pH 5.5 to pH 8.0 with buffers of 0.5 M ionic strength. The same IMAC adsorbents were also investigated for their protein binding capabilities with buffers of an ionic strength of 0.06 M at pH 5.5 and pH 8.0. The binding behaviour of four "marker" proteins, namely transf errin, alpha(2)-macrogrobulin, gammaglobulin and human serum albumin have f urthermore been employed to monitor the differences in protein selectivity exhibited by these IMAC systems. The experimental findings confirm that the se hard Lewis metal ion IMAC adsorbents function in a "mixed" binding mode with both coordination and electrostatic characteristics evident, depending on the ionic strength and pH of the equilibration or elution buffers. Base d on a screening protocol, several members of the im-Mn+-8-HQ and im-Mn+-OP S adsorbent series have been identified with high selectivity for transferr in and alpha(2)-macroglobulin. These hard Lewis metal ion IMAC adsorbents t hus provide attractive alternatives for selective fractionation of human se rum proteins. (C) 2000 Elsevier Science B.V. All rights reserved.