Predispensed gradient matrices - a new rapid method of finding crystallization conditions.

Predispensed gradient matrices allow the boundary between precipitate and clear solution to be located very rapidly for a particular protein and precipitant. In many cases crystals grow in the trials which were used to identify this boundary. The method involves dispensing a series of between 10 and 72 microbatch trials in which some parameter, such as precipitant concentration, is gradually changed. (Protein is not dispensed at this stage.) Protein is then added to selected trials using a predetermined algorithm, which takes into account the level of precipitation caused by previous additions. Thirteen crystal forms were obtained using the method with eight proteins and eight precipitants. Six forms were prisms or plates with maximum dimensions above 400 microm.