Study of the aggregates in lysozyme solution before crystal growth

The aggregates in lysozyme solution with different NaCl concentrations in which nuclei have not appeared were studied by dynamic light scattering (DLS) method. In addition, the aggregates absorbed on the silicon wafer surface were observed by atomic force microscope (AFM). The results showed that when the NaCl concentration was lower than 0.4 mol L - 1 , the higher the NaCl concentration was, the smaller the dimension of the aggregates was. The big aggregates disappeared and only aggregates with the dimension of 3 ∼ 4 nm in lysozyme solution remained when NaCl concentration was 0.4 or 0.5 mol L - 1 . The result of Zeta potential showed the change of the interaction between NaCI and lysozyme molecules. From the experimental results, we conclude that lysozyme crystal could not grow in solution in the presence of amorphous aggregates bigger than 100 nm in dimension. Additionally, the difference between results of DIS and AFM was analyzed.