Marcus Winter
Fri, 05 Feb 2010 07:01:12 -0800
Dear Rui, Perhaps this is another instance where the PX Scanner might prove so helpful ? Maybe, amongst your many crystals - all of which 'look' not too bad ... there are one or two which actually diffract much further beyond the 2.9Å which you mentioned ? However, unfortunately, you're just not happening to choose either of those for looping out. The Oxford Diffraction PX Scanner system can assess the diffraction qualities of crystals in situ - in the crystallisation plate. So, directly, you would discover if your crystals actually diffract well... in their mother liquor under ambient conditions and before the addition of any cryo-protect. Do you have a friend or neighbour with a PX Scanner ? If not, please feel most welcome to contact Oxford Diffraction: we would be pleased to assist if at all possible. Good Luck and Best Wishes, Marcus Winter. www.oxford-diffraction.com ________________________________ From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of rui Sent: 05 February 2010 14:48 To: CCP4BB@JISCMAIL.AC.UK 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