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
