Automation of non-conventional crystallization techniques for screening and optimization

Abstract

The availability of high-quality crystals is crucial to the structure determination of proteins by X-ray diffraction. It is still not understood why some proteins crystallize with ease while others stubbornly refuse to produce suitable crystals. Producing high-quality crystals has always been the bottleneck to structure determination and with the advent of structural genomics this problem is becoming increasingly acute. In spite of impressive advances in throughput, the crystallization problem has not been solved and better crystallization techniques need to be designed in order to overcome this hurdle. Finding favourable conditions for crystallization is usually achieved by screening of the protein solution with numerous crystallizing agents in order to find 'hits' that indicate which conditions may be suitable for crystal growth. Optimization of the crystallization conditions is done either by fine tuning of the parameters (precipitant, pH, temperature, additives, etc.) involved, or by manipulation of the crystallization phase diagram with the aim of guiding the experiment in the direction that will produce the desired results. This chapter highlights a variety of non-standard experimental methods of screening and optimization techniques with a focus on those that have been automated and can be adapted to high-throughput trials.