On Fri, Feb 5, 2010 at 7:43 AM, Enrico Stura <[log in to unmask]> wrote:

On Fri, 05 Feb 2010 05:39:14 +0100, rui <[log in to unmask]> 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
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