Lysozyme crystal nucleation in solution layers

作者：Hodzhaoglu F V; Stanoeva L N; Nanev C N^*

来源：Bulgarian Chemical Communications, 2011, 43(3): 361-369.

• protein crystal nucleation
• thin protein solution layers
• heterogeneous vs. homogeneous nucleation
• crystal nucleants of biological origin

By using the classical approach of separation in time of nucleation and growth stages, protein crystal nucleation was investigated in thin protein solution layers confined between two glass plates of custom made quasi two-dimensional all-glass cells. Solution layer thickness was varied from 0.05 down to 0.01, 0.0065 and 0.002 cm. Two commercial samples of hen-egg-white lysozyme, HEWL, Seikagaku 6 times crystallized and Sigma 3 times crystallized, were used as model proteins. The number. of HEWL crystal nuclei decreased with diminishing solution layer thickness but the crystal nuclei reduction was considerably lesser than proportional to solution layer diminish. Heterogeneous (on-glass) protein crystal nucleation was separated from bulk one in 0.05 cm solution layers,. the corresponding nucleation rates being measured separately. Up to 80% of the crystal nuclei were formed heterogeneously, on the glass, from 0.05 cm protein solution layers of Seikagaku HEWL. On the contrary, only 10 to 13% of the nuclei were observed on glass under the same conditions in Sigma solution; bulk nucleated crystals represented the main crystal fraction in this case. A plausible explanation of the experimental results was suggested. It is that the bulk crystal nucleation occurs on rests of source biomaterial that are always present in the protein solutions. Moreover, they may be even more active nucleants than the glass.

• 出版日期2011