W0265

The Effect of Solution Parameters on Lysozyme Nucleation Rates and Crystal Quality. R.A. Judge & E.H. Snell Code ES76, NASA MSFC, Huntsville AL 35802

In the pursuit of strongly diffracting high quality macromolecule crystals of suitable volume, this study investigates how the formation of macromolecules in solution and their growth characteristics effect crystal volume and diffracting quality.

We systematically investigated the effect of solution conditions on lysozyme nucleation rates and the volume of crystals produced. Batch crystallization plates were used in combination with a video microscope system to measure nucleation rates and crystal volume. As expected from classical nucleation theory, crystal numbers were found to increase with increases in temperature and supersaturation. Small changes in solution pH, at constant supersaturation values were found however to dramatically effect the number of crystals nucleated in the wells varying from 1000s to 10s in the pH range 4.0 to 5.2.

Having optimized the conditions required to produce an appropriate number of crystals of a suitable volume for X-ray analysis, a large number of uniform crystals were produced under exactly the same conditions. In the X-ray analysis of more than 50 such crystals there was found a wide variation in crystal lattice parameters and data quality. The variation in X-ray quality crystal samples is thought to be related to the growth rate variation caused by growth rate dispersion seen in lysozyme crystal growth experiments.