MPI tray: a versatile crystallization plate for membrane proteins

High-throughput crystallization of biological macromolecules is usually performed on multi-well plates, the design of which needs to address different and sometimes conflicting requirements. In this regard, handling of membrane proteins presents a particular challenge owing to the common use of detergents with associated effects on surface tension. Reported here is the design of a new crystallization plate, termed the MPI tray, which is optimized for UV and visible imaging with membrane protein samples. Following basic considerations regarding geometry and material, the surface properties of the plate were subjected to extensive analysis and modification in order to improve the performance in a robotic environment. An electrostatic surface potential was identified as the major problem affecting the automated setup of experiments, and it was found that treatment of the crystallization plate with ethanol is effective in removing this potential.