CONTINUING ADVENTURES IN LYSOZYME CRYSTAL-GROWTH

Tetragonal lysozyme solubility decreases with increasing salt concentrations and decreasing temperatures. The interaction of lysozyme with Cl- appears to be more complex than previously thought. An excess of Cl- over the available basic residues was found associated well before the protein saturation concentration was reached. Aggregation was found to involve the replacing of the protein-Cl- with protein-protein interactions. The aggregation process itself has been found to be kinetically, not collisionally controlled. Aggregation occurs at the expense of monomer concentrations. By approximately 3 x supersaturation, monomer concentrations are essentially level, rising only slightly through the concentrations typically used for lysozyme crystal growth. Lysozyme (110) face growth rates were found to be highly dependent upon both the precipitant concentration and temperature. Conditions which lead to lower solubilities in the phase diagram resulted in a shift of the growth rate versus supersaturation ratio curve to the right; i.e., higher supersaturation ratios were required for equivalent (110) face growth rates when either the temperature was decreased or the NaCl concentration increased. Finally, the (110) face growth rate of tetragonal lysozyme was progressively inhibited by continued exposure to solution flow. The rate at which the growth rate was inhibited increased with the solution velocity.