A simple and efficient innovation of the vapor-diffusion method for controlling nucleation and growth of large protein crystals

The rate of water vaporization in the vapor-diffusion method is critical fo r the protein crystallization process. Present methods, however, allow litt le or no control of the equilibration rates. This paper presents a relative ly simple innovation of the conventional vapor-diffusion method by introduc ing a capillary barrier (for hanging drop) or a punched film barrier (for b oth hanging and sitting drop) between drop and reservoir, which can be bene ficial in controlling the water vaporization rate, thereby promoting growth of large protein crystals. The crystallization experiments for lysozyme, t richosanthin and a novel neurotoxin BmK Mu9 show that this modified vapor-c ontrolling-diffusion method is very effective for producing large protein c rystals. The improved technique can be routinely used as a method for the p reparation of other macromolecular and small-molecule crystals whose crysta llization involves vaporization of water.