Interfacial functional terminals enhance the heterogeneous nucleation of lysozyme crystals

A series of functional terminals were designed to interact with the flexible loop residues of lysozymes, aiming to produce quality protein crystals via intensified heterogeneous nucleation. On the acetamidophenyl (S-PhAc) terminals, the obtained lysozyme crystals have the largest modal size of about 270 mu m. The in situ liquid-cell AFM images reflect the fact that the particle aggregation rate is greatly associated with the functional terminals at the beginning of crystallization, i.e., the fast rate is achieved as 0.088 +/- 0.004 nm s(-1) on S-PhAc, much higher than that on commercial siliconized square cover slides (0.025 +/- 0.005 nm s(-1)). Combining the crystallization results with molecular modeling, it is indicated that the stronger the interactions between lysozyme loop residues and the functional terminals, the more easily the heterogeneous nucleation occurs. It is suggested that designing functional terminals targeting the feature loop residues of proteins would be a promising route to modulate protein crystallization at the early stage.