Experimental and in silico studies on three hydrophobic charge-induction adsorbents for porcine immunoglobulin purification

Three hydrophobic charge-induction adsorbents with functional ligands of 4-mercapto-ethyl-pyridine, 2-mercapto-methyl-imidazole or 2-mercapto-benzimidazole were evaluated in the purification of porcine immunoglobulin from porcine blood. Adsorption isotherms were studied under different pH conditions. The adsorbent with 2-mercapto-methyl-imidazole as the ligand showed reasonable adsorption capacity (43.60 mg·g− 1 gel) with great selectivity and it also showed the best elution performance in chromatographic studies. A multi-pH step elution process was proposed for the 2-mercapto-methyl-imidazole adsorbent, and the results showed that high immunoglobulin purity (94.3%) and a yield of 9.8 mg·(ml plasma)− 1 could be achieved under the optimal condition of loading (pH 5.0)–pre-elution (pH 7.0)–elution (pH 3.8). Moreover, molecular simulation was employed to help in analyzing the binding mechanism between the ligands and immunoglobulin, and the results showed that both 2-mercapto-benzimidazole and 2-mercapto-methyl-imidazole ligands were docked on the same pocket (around TYR319 and LEU309) of the Fc fragment of immunoglobulin, with 2-mercapto-benzimidazole showing stronger binding interactions.

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