Meanwhile, at a separate station, a syringe deposits a mixture of the protein and the appropriate mother liquid on each of 48 circular transparent cover slips. As the cassette is stepped through, each row of eight slips is inverted and sealed over the corresponding wells. The robot needs six minutes to set up and seal the 48 cover slips for a cassette, which sets the rate of the entire coarse-screening preparation process. The cassettes are automatically stored at constant temperature after filling. Water slowly diffuses from the hanging drop into the mother liquid in the reservoir, and the concentration of protein increases.
Crystals precipitate in some of the reservoirs.
We're trying to get crystallization with a few nanoliters of protein instead of microliters-a reduction by a factor of a thousand. We will see crystals within a few hours to a few days. Solutions that don't produce good results are rejected. The preliminary system has been successfully tested for reliability, consistency, and speed on commercially available proteins and on novel proteins from the laboratories of Schultz and Stevens. Before long, they hope to see the full system in regular use at the Advanced Light Source and elsewhere.