THE EFFECTS OF TEMPERATURE AND NACL CONCENTRATION ON TETRAGONAL LYSOZYME FACE GROWTH-RATES

Measurements were made of the (110) and (101) face growth rates of the tetragonal form of hen egg white lysozyme at 0.1M sodium acetate buff er, pH 4.0, from 4 to 22-degrees-C and with 3.0%, 5.0%, and 7.0% NaCl used as the precipitating salt. The data were collected at supersatura tion ratios ranging from approximately 4 to approximately 63. Both dec reasing temperature and increasing salt concentrations shifted plots o f the growth rate versus C/C(sat) to the right, i.e. higher supersatur ations were required for comparable growth rates. The observed trends in the growth data are counter to those expected from the solubility d ata. If tetragonal lysozyme crystal growth is by addition of ordered a ggregates from the solution, then the observed growth data could be ex plained as a result of the effects of lowered temperature and increase d salt concentration on the kinetics and equilibrium processes governi ng protein-protein interactions in solution. The data indicate that te mperature would be a more tractable means of controlling the growth ra te for tetragonal lysozyme crystals contrary to the usual practice in, e.g., vapor diffusion protein crystal growth, where both the precipit ant and protein concentrations are simultaneously increased. However, the available range for control is dependent upon the protein concentr ation, with the greatest growth rate control being at the lower concen tration.