Hi Uwe,
Just what I wanted to hear, and with a limited set of compounds too!
Follow-up question: what are these 4-6 most successful compounds?
Thanks also for the tips on monitoring thw soaking
Derek
On Sep 25, 2007, at 13:23, Uwe Mueller wrote:
Dear Derek,
we are using the quick-soak method frequently at the BESSY-MX
beamlines. So far we were able to obtain phase information in terms
of MAD/SAD- phases in all cases which we tried. The starting set-up
is the screen over the 4-6 most successful heavy atom compounds at
5-10mM concentration and 10-20 min soaking time.
If you follow the soaking under a transmissive light microscope
like the Leica MZ7.5, you can receive quite intriguing visual
feedbacks from your experimental set-up, including the bending of
large crystal face areas towards the crystal center due to the
large osmotic pressure at the beginning of the process an others.
Those observations might provide you further information for the
optimization loop which will be confirmed by the detection of an
anomalous signal after the peak-dataset.
3-8 of such fast feedback loops could be carried out within a 8h
beamtime shift and led to interpretable electron densities. So, I
regard this method as a very powerful alternative, where the
availability of SeMet-crystals is limited.
Best regards,
Uwe
Derek Logan schrieb:
Hi,
I'd like to find out how successful the "quick soak" method for
heavy atom derivatisation proposed by Radaev and Sun:
Sun PD, Radaev S, Kattah M. Generating isomorphous heavy-atom
derivatives by a quick-soak method. Part I: test cases. Acta
Cryst. 2002. D58:1092-1098.
has been in comparison to the "classical" method of longer soaks
at low concentrations of heavy atom compound. The method was quite
successful in our hands a few years ago but (fortunately?) it's
becoming increasingly rare that we use heavy atoms. I understand
that evidence will necessarily be anecdotal, but let's not let
that stop us.
Derek
--
Derek Logan tel: +46 46 222 1443
Associate professor fax: +46 46 222 4692
Molecular Biophysics mob: +46 76 8585 707
Lund University
Box 124, Lund, Sweden
--
_______________________________
Dr. Uwe Müller
BESSY-MX group BESSY GmbH
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Phone: +49-(0)30-6392 4974
Fax : +49-(0)30-6392 4975
email: [EMAIL PROTECTED]
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