Rui-- It is not uncommon to see "hollowed ends" on crystals when they grow quickly at that point. You have received some very good suggestions thus far, and slowing down the growth might also be helpful. We have had good success doing this by just varying the protein concentration and/or the precipitant concentrations. We have also had good luck substituting sodium malonate for the ammonium sulfate in our optimizations.
HTH! annie Annie Hassell Glaxo Smithkline 5 Moore Drive RTP, NC 27709 919/483-3228 919/483-0368 (FAX) annie.m.hass...@gsk.com "rui" <ruis...@gmail.com> Sent by: "CCP4 bulletin board" <CCP4BB@JISCMAIL.AC.UK> 05-Feb-2010 09:48 Please respond to "rui" <ruis...@gmail.com> To CCP4BB@JISCMAIL.AC.UK cc Subject Re: [ccp4bb] how to improve resolution Hi, Thanks all for the good suggestions, I just attached two images that show my crystals, maybe you'll see new problems with the conditions. Thanks again. On Fri, Feb 5, 2010 at 7:43 AM, Enrico Stura <est...@cea.fr> wrote: On Fri, 05 Feb 2010 05:39:14 +0100, rui <ruis...@gmail.com> wrote: Hi, All, We are trying to crystallize a protein and found some initial hit in the following conditions, pH 4.8, 0.2 M AS or some other salts ( NaCl,LiCl, MgCl2 ), 32% PEG4000 or PEG3350 ). However the quality of the crystal is not so great,some of them look like needle cluster(very long in length), some of them look like multi-crystals or hollow inside. Such growth problems are likely due to the quality of the protein solution. Changes in precipitant concentrations are likely to be ineffective. Try ion exchange purification. We tried to optimize the pH and PEG and tested one that diffracts at 2.9A. For the next, how to improve resolution?Any suggestions? Even mutate the protein to get a high resolution is ok, generally what kind of mutation would make proteins crystallize better? Thanks. It is not mutations that will improve diffraction, it is small changes in crystal contacts. The Discussion section from: http://pubs.acs.org/cgi-bin/article.cgi/cgdefu/2007/7/i11/html/cg700698d.html may help. Enrico -- Enrico A. Stura D.Phil. (Oxon) , Tel: 33 (0)1 69 08 4302 Office Room 19, Bat.152, Tel: 33 (0)1 69 08 9449 Lab LTMB, SIMOPRO, IBiTec-S, CEA Saclay, 91191 Gif-sur-Yvette Cedex FRANCE http://www-dsv.cea.fr/en/ibitecs/82 http://www.chem.gla.ac.uk/protein/mirror/stura/index2.html e-mail: est...@cea.fr Fax: 33 (0)1 69 08 90 71 [attachment "Fig1.JPG" deleted by Annie M Hassell/PharmRD/GSK] [attachment "Fig2.JPG" deleted by Annie M Hassell/PharmRD/GSK]
