Site-specific immobilization of lysozyme upon affinity chromatography resin by forecasting lysine activity and...

Here, a site-specific immobilization strategy for lysozyme was discussed. First, we calculated the surface micro-environment of lysozyme as a model protein and forecasted the nucleophilic attack activity order of six lysine residues within lysozyme, namely, K96> K97 and K33>K1, K13, and K116. Second, lysozyme was immobilized on agarose resin (epoxy group density 22.34 μmol/g) and incubated at pH 9.5 for 12 h. We then compared the peptide maps of free and immobilized lysozyme and established a quantitative detection method for immobilization sites. Third, we studied the effect of immobilization conditions such as epoxy group density and pH upon immobilization sites. When lysozyme was immobilized upon resin with a high epoxy group density (22.34 μmol/g) at pH 9.5 for 12 h, multiple lysozyme immobilization sites were found, including K33, K96 and K97; when lysozyme was immobilized upon resin with a low epoxy group density (11.36 μmol/g) at pH 9.5 for 12 h, only one lysozyme immobilization site was found, K96. The pH also had an effect upon immobilization sites. When immobilization was performed at pH≥10.5 with low epoxy group density resin (11.36 μmol/g) for 12 h, the immobilization sites included at least K33, K96 and K97; when immobilization was performed at pH 9.5 with other conditions remaining unchanged, the only lysozyme immobilization site found was at K96. These experimental results were highly consistent with the forecasted results, revealing some regularities of immobilization site control for lysozyme upon affinity chromatography resin.