[ccp4bb] stacked thin plates
Deal all, Sorry for the non-ccp4 query once again. I need suggestions regarding the improvement in crystal quality. I have crystallized a protein in MPD. The crystals grow like a thin plates and the plates are stacked together. So, the mosaicity is very high and also indexing is difficult even at 2 angstrom data set. All suggestions are welcome. Thanks. James.
Re: [ccp4bb] stacked thin plates
James, I think the standard suggestions apply. Try to tweak your crystallization conditions to get a single crystal (i.e. not a series of stacked plates). PEG 400 can be a good substitute for MPD, but you could also try additive screens as well as co-crystallization with products, cofactors, substrates, analogs, etc. to alter the crystallization. Alternatively, seek out a beamline that offers X-ray beam diameters of 5-20 microns. You can survey your entire crystal(s) for very small diffracting volumes that might only contain a single plate. You may get lucky. -Andy === Andrew T. Torelli Ph.D. Postdoctoral Associate Department of Chemistry Chemical Biology Baker Laboratory, Cornell University Ithaca, NY 14853 === On 9/3/2009 8:40 AM, james09 pruza wrote: Deal all, Sorry for the non-ccp4 query once again. I need suggestions regarding the improvement in crystal quality. I have crystallized a protein in MPD. The crystals grow like a thin plates and the plates are stacked together. So, the mosaicity is very high and also indexing is difficult even at 2 angstrom data set. All suggestions are welcome. Thanks. James.
Re: [ccp4bb] stacked thin plates
We had a similar situation: great diffraction, multiple lattices due to stacked plates that appeared to be single crystals. We ran an additive screen with about a dozen common salts and solvents, e.g., AmSO4, LiCl, MgSO4, AmPO4, PEG400, EG, glycerol, DMSO, etc. at 100 mM for salts or 5-10% for liquids in our best crystallization conditions. AmSO4 and EG changed the crystal form slightly to more blocky plates. Those additives were screened from 50-200 mM and 75 mM AmSO4 was the winner: single crystals that diffracted to 2.4 A, slightly worse than the 2.0 for the stacked plates, but good enough to get a structure. Cheers. james09 pruza wrote: Deal all, Sorry for the non-ccp4 query once again. I need suggestions regarding the improvement in crystal quality. I have crystallized a protein in MPD. The crystals grow like a thin plates and the plates are stacked together. So, the mosaicity is very high and also indexing is difficult even at 2 angstrom data set. All suggestions are welcome. Thanks. James. -- Roger S. Rowlett Professor Department of Chemistry Colgate University 13 Oak Drive Hamilton, NY 13346 tel: (315)-228-7245 ofc: (315)-228-7395 fax: (315)-228-7935 email: rrowl...@mail.colgate.edu
Re: [ccp4bb] stacked thin plates
Have you tried using these crystals to produce seeds for matrix seeding? charlie Deal all, Sorry for the non-ccp4 query once again. I need suggestions regarding the improvement in crystal quality. I have crystallized a protein in MPD. The crystals grow like a thin plates and the plates are stacked together. So, the mosaicity is very high and also indexing is difficult even at 2 angstrom data set. All suggestions are welcome. Thanks. James.
