Surfactant-assisted crystallization of lysozyme and its mechanism

Surfactants were used to assist crystallization of lysozyme. Three types of surfactants with different structures (sodium dodecyl sulfate, cetyltrimethyl ammonium bromide, or betaine hydrochloride (BH)) were used. The study indicated that three surfactants were all capable of shortening the crystallization induction time of lysozyme, with BH inducing the shortest crystallization induction time (t=1 min) and the largest crystal size (37 μm). The molecular interactions among each of the three surfactants abovementioned and lysozyme was also investigated by simulations. It was found that hydrogen bonding dominantly acted between the carboxyl structure of the surfactant BH and the lysozyme, which produced the most favorable conformation for the self-assembly of lysozyme (promote lysozyme orderly aggregation and shorten the crystallization induction time). On this basis, the mechanism of surfactant-promoted lysozyme crystallization was proposed.