Phosphorylated-tyrosine based pseudobioaffinity adsorbent for the purification of immunoglobulin G

The present study evaluated the phosphorylated-tyrosine (P-Tyr) based pseudobioaffinity adsorbent for the purification of human immunoglobulin G (IgG). P-Tyr was selected as a ligand to mimic the natural interactions that occur between the immunoreceptor tyrosine-based activation motif and the IgG. The ligand was coupled to bisoxirane-activated agarose gel and the effect of buffer system, pH, and conductivity was performed to elucidate the nature of IgG-P-Tyr interactions. P-Tyr-agarose was able to purify IgG from human plasma solution in HEPES buffer at pH 7.0 exhibiting a purification factor of 9.1 with IgG purity of 91% (based on ELISA analysis of albumin, transferrin, and immunoglobulins A, G, and M). The evaluation of different functional groups of P-Tyr on the adsorption of human IgG indicated the predominance of electrostatic interactions with phosphate groups, although the contributions of aromatic and carboxylic groups also play a role. The thermodynamic parameters (ΔH°, ΔS°, ΔG°) for IgG adsorption onto P-Tyr-agarose were determined from the temperature dependence. The maximum IgG binding capacity at 20°C was 273.51±12.63mgg^-1 and the dissociation constant value of the complex IgG-P-Tyr was in the order of 10^-5molL^-1 indicating low-affinity.