LIGAND STRUCTURE OF THE DIVINYLSULFONE-BASED T-GEL

The requirements for divinylsulfone (DVS)-based gels to act as thiophi lic adsorbents, binding immunoglobulins in a salt-dependent manner hav e been examined. No differences in protein binding were observed for a DVS-activated gel reacted with mercaptoethanol (the T-gel), or for th e same gel treated at high pH to hydrolyse the active groups and/or al low the formation of cross-links within the matrix, indicating that an O atom may be substituted for the thioether without affecting the thi ophilic interactions. Extending the time of the activation reaction be tween DVS and the matrix results in increased amounts of sulfone attac hed to the gel, but decreased levels of active vinyl groups. When coup led to mercaptoethanol, these adsorbents bound more IgG than gels acti vated for shorter periods. This provides a convenient method to prepar e thiophilic adsorbents of high capacity while minimising the amount o f DVS used. The immobilised vinylsulfone must be linked to an electron donating atom for IgG to bind. When the vinyl was instead reduced wit h sodium borohydride, protein binding was decreased. No IgG bound to a mine-coupled DVS-activated adsorbents, perhaps due to an overall posit ive charge on these gels at pH 7.4. The binding of human IgG to the ad sorbents is dependent on ligand density, with little protein binding t o gels having less than 16 mu mol sulfone per mi. The binding increase d with the ligand density above this level, with more than 25 mg IgG b inding per mi to an adsorbent having 114 mu mol sulfone per mi. The la ck of binding at low ligand densities would be expected if the IgG mus t interact with two or more sulfone ligands to be retained on the adso rbent. (C) 1997 Elsevier Science B.V.