Result: A simple modification of the Q-plate for parallel screening and combinatorial crystallization

In many cases it can be advantageous to screen crystallization conditions in parallel. Tasks, such as the setting up a standard screen for several proteins simultaneously or analyzing the effect of drop size and different precipitant-protein drop ratios can be done more efficiently when drops are set up in parallel using a common reservoir. However, a real need for parallel screening becomes apparent when analyzing a large number of different complexes of the same protein, or when using methods such as stoichiometry variation screening and other combinatorial crystallization methods. Because of its large size, the Q-plate is easily adapted to the screening of a variable number of sitting drops in parallel. The drops are set up on a single glass slide placed over the same reservoir solution. The modification is simple and does not require a robot although it is well suited for automation. A record of each drop in multi-drop setup is kept as an HTML-file which allows for rapid navigation between experiments. Flexibility in the number drops makes the method effective for most combinatorial and non-combinatorial applications.