[ccp4bb]: protein mass per Se in MAD experiments

["Savvas N. Savvides" <savvas.savvides@vub.ac.be>]

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Dear colleagues,
which structure determination is the current champion of the ratio of
protein molecular weight per Se atom used for phasing in MAD/SAD methods.
Unpublished information in the disguise of fictitious protein names are also
welcome!

The rule of thumb for this kind of ratio used to be 10 kDa of protein per Se
atom, but I suspect that with the technological/methodological advancements
we have all been experiencing this number may have gone up.

Sincerely
Savvas

--------------------------------------------
Savvas N. Savvides
Department of Ultrastructure - VIB
Free University of Brussels
Pleinlaan 2
Building E, room 4.4
1050 Brussels
Belgium
Tel. +32-2-629.18.48  Fax. +32-2-629.19.63
Email.  savvas.savvides@vub.ac.be
--------------------------------------------


-----Original Message-----
From: owner-ccp4bb@dl.ac.uk [mailto:owner-ccp4bb@dl.ac.uk]On Behalf Of
N.Manoj
Sent: Wednesday, February 12, 2003 8:48 PM
To: ccp4bb@dl.ac.uk
Subject: [ccp4bb]: substrate soaking into crystals


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Dear all,
           I am trying to get cocrystals with ATP bound in the active
site.  But the electron density maps show no evidence of ATP binding. I
have ~200mM ammonium sulphate, PEG and 4mM ATP in the crystallization
conditions and most probably ammonium sulphate competes with the ATP,
preventing its binding.
Does anyone know of a case where the ammonium sulphate has been
exchanged or replaced from the crystals by soaking etc and found
competing substrates being bound after that?
Thanks in advance

manoj