CRYSTALLIZATION OF PROTEINS BY DYNAMIC CONTROL OF EVAPORATION

It is expected that the kinetics of supersaturation, which is directly related to the evaporation of solvent from a crystallization solution, will greatly affect both nucleation and crystal growth processes. Therefore, a novel device has been developed which allows computer regulation of the flow of N2(g) over a hanging drop to dynamically control the evaporation of solvent. A thermal conductivity detector is used to monitor the amount of water vapor transferred from the drop to the gas stream and provides closed loop control of the evaporation process. Data acquisition and control are accomplished using a custom program written with LabVIEW software (National Instruments) on a Macintosh II microcomputer. Quantitation of several evaporation protocols has been accomplished using both the thermal conductivity detector and a novel conductance cell that allows continuous measurement of solution analyte concentrations. Crystals of hen egg white lysozyme have been grown at different evaporation rates and analyzed according to size and number of single crystals.