Crystallization-grade protein

Obtaining X-ray quality crystals is often the most difficult step of a structure determination. Strong and dedicated support in molecular biology and biochemistry is an absolute must for the production of sufficient quantities of crystalhzation grade protein. When the crystallization conditions are not known, one often needs as much as 100 mg of protein to find the right crystallization conditions. In most cases, several protein constructs or protein variants need to be generated until one is found which is amenable to crystallization. AVhen crystallization conditions are already known and one is lucky, 1 mg of protein may be enough to produce a series of crystals with different inhibitors. One should bear in mind, however, that published crystallization protocols are often difficult to reproduce In such cases, particular attention should be paid to small differences in the protein construct or in the purification protocol, which can have a dramatic influence on crystallization behaviour. 

Material. 3 X crystallized, dialyzed and lyophilized Grade 1 Hen Egg White Lysoz3mie was obtained from Sigma Chemical Company, and used without further purification. Purity of the protein was verified by both gel electrophoresis on acrylamide and chromatography on a column packed with anion exchange resin (Cl form) Sephadex DEAE. The sample showed a single peak in these analyses. 

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