Effects of solution stirring on protein crystal growth

We report the influence of solution stirring on the growth of hen egg white lysozyme crystals. Solution stirring rate was controlled by varying the rotation speed of a rotary shaker. A range of precipitation agent (sodium chloride) concentrations was also investigated. The time required for crystal nucleation to occur was observed to be much greater in stirred samples than in unstirred samples. Solution stirring resulted in a reduced number of crystals (at sodium chloride concentrations from 6 to 9%). These crystals were larger and of a higher quality. However, the time required for nucleation to occur was reduced by gentle stirring (25 and 50rpm) in a 12.5% sodium chloride concentration solution, suggesting that stir-ring can stimulate nucleation. These results indicate that the optimization of solution stirring rates is a useful technique for controlling protein, crystal growth.