A MACROMOLECULAR CRYSTALLIZATION PROCEDURE EMPLOYING DIFFUSION CELLS OF VARYING DEPTHS AS RESERVOIRS TO TAILOR THE TIME-COURSE OF EQUILIBRATION IN HANGING-DROP AND SITTING-DROP VAPOR-DIFFUSION AND MICRODIALYSIS EXPERIMENTS

A procedure and crystallization plate are described that allow control over the time course of equilibration between a macromolecule and a r eservoir solution. The d2 dependence of diffusion is exploited in a cr ystallization plate with reservoirs of varying depths to speed up or s low down the equilibration. A rationale is presented that suggests why this might be useful. The plate is a completely passive device, with no moving parts, that can be set up in about the same time as a tradit ional 24-well plate. It can, with equal facility, be used for hanging- drop or sitting-drop vapor diffusion or microdialysis crystallization experiments. The procedure has been used to grow very large diffractio n-quality crystals of three protein-inhibitor complexes, one of which had failed to yield any but microcrystals by more traditional methods.