LAUSR

Abstract Five tryptophan analogues with a hydrophobic indole ring and an amino group on each molecule were used as functional ligands of mixed-mode resins for human serum albumin (HSA) purification. Their adsorption performance was evaluated and the effects of pH and salt addition on HSA adsorption were studied. The resins prepared showed typical pH-dependent adsorption and the highest adsorption capacity and affinity were found at pH 5.0 for all the resins tested. The saturated adsorption capacity was 138.02 mg·g− 1 with the tryptamine-functionalized resin, which significantly decreased at pH below 4.0 due to electrostatic repulsion between ligands and HSA. Moreover, the addition of NaCl or (NH4)2SO4 in media reduced HSA adsorption capacity, although the two salts showed different affecting profiles. The tryptamine-functionalized resin showed the best salt-tolerant performance, and its high adsorption capacity was maintained under high salt concentrations. In addition, the five resins prepared showed good adsorption selectivity for recombinant HSA from Pichia pastoris broth. Molecular docking results between tryptamine and HSA indicated that tryptamine was favorable to bind on Site II (indole-binding site) of HSA.