The temporal and spatial growth behaviour of protein crystals

subject to different cooling strategies in protein crystallisation was investigated. Although the impact of temperature and cooling rate on crystal growth of small moleculeswaswell documented

much less has been reported on their impact on the crystallisation of proteins. In this paper

an experimental set-up is configured to carry out such a study which involves an automatic temperature controlled hot-stage crystalliser fittedwith a real-time imaging system. Linbro parallel crystallisation experiments (24-well plate)were also conducted to find the suitable initial conditions to be used in the hot-stage crystallisation experiments

including the initial concentration of HEWlysozyme solutions

precipitate concentration and pH value. It was observed that fast cooling rates at the early stage led to precipitates while slow cooling rates produced crystal nuclei

and very slowcooling rates

much smaller than for smallmolecules are critical to the growth of the nuclei and the crystals to a desired shape. The interesting results provide valuable insight aswell as experimental proof of the feasibility and effectiveness of cooling as a means for achieving controlled protein crystallisation

compared with the evaporation approach which was widely used to grow single large crystals for X-ray diffraction study. Since cooling rate control can be easily achieved and has good repeatability

it suggests that large-scale production of protein crystals can be effectively achieved by manipulating cooling rates.