Dear James: It is extremely hard to make generalizations, but if it takes months for crystals to appear, the following questions are worth asking:
1. Is the actual concentration of macromolecule, precipitating agent, etc required for crystallization higher than what you are using? A closed vapor diffusion chamber is somewhat permeable to water vapor, and in the course of five months, you could easily lose half of the water. Try doubling the protein concentration, or crank up the concentration of one or more components in the reservoir solution. 2. Is the actual macromolecule you crystallized the same as what you started with? Slow degradation, or proteolysis, may be taking place, and the crystals you are growing are something else. (Similarly, if you have a cofactor or coenzyme, as these could slowly decompose into the critical ingredient for crystallization). 3. It might be too cold, and warming things up a bit might speed up crystallization. Hopefully that will get you started before the experts reply. Bill On Sun, October 11, 2009 8:27 am, james09 pruza wrote: > Dear crystallographers, > > Sorry for the non-ccp4 query. I am new to this field and need some > suggestions. My question is, why some protein takes longer time to > crystallize, say 6-8 months, and it is the only condition to get the > crystals.? What are the ways to get the crystals faster. > > The crystal appears with 60% of 2-Methyl, 2-4 Pentane Diol and only at 4 > degree with very low concentration of NaCl. I have got some of the > sugggestions earlier from the CCP4-discussion board for microseeding, but > it > did not work. > > All suggestions from the experts are welcome. > > Thanks. > James > William G. Scott Contact info: http://chemistry.ucsc.edu/~wgscott/