Crystallization trials are rapidly set up in Hampton 24-well plates. Each well is sealed with either a plastic or a siliconized-glass coverslip. Check plates at least once per week, but not too often because temperature variation may impede crystal growth. Focused grid screening Once crystals are obtained from screening. Prepare crystallization solutions for a focussed screen around the initial conditions.
Primary variables are precipitant concentration, pH and protein concentration.
All three dimensions can be tested on one plate if several protein drops of different concentration are suspended on one coverslip. Secondary variables include subtle differences in precipitant and buffer type and the presence of additives such as detergents or multivalent salts.