THE INFLUENCE OF IMPURITIES ON PROTEIN CRYSTALLIZATION - THE CASE OF LYSOZYME

Several batches of hen egg white lysozyme were compared on the basis of their biochemical purity and homogeneity as well as of their ability to crystallize in the tetragonal space group in the presence of sodium chloride and sodium acetate at pH 4.5. Trace amounts (< 2% (w/w)) of detectable protein impurities and inactive lysozyme molecules interfere with the nucleation and crystal growth processes. The presence of impurities significantly decreases solubility of lysozyme preparations. The intentional addition of ovalbumin or bovine serum albumin to pure lysozyme is correlated with an increase of the proportion of twinned crystals. Thus, reproductibility of lysozyme crystallization is dependent upon the presence of impurities.