Hi,
Mercury will likely form a precipitate with you SCN- anions...
solubility in water is 0.6 g/L (about 3 mM) at 25°C...
Since you are not in water, at less than 25°C, and with you high
concentration of SCN- ions, don't expect to have high concentrations of
*soluble* Hg++ in you medium. Prolongated soaking migh well allow some
Hg++ to dissolve from Hg(SCN)2 and go into your crystal... but will this
be okay for your synchrotron trip on saturday ??
I would therefore not rely only on HgII salts for this trip. With about
40 crystals, you might want to try other compounds.
good luck !
Laurent
David Briggs a écrit :
Hi Sebastiano,
Free Cys' are crying out for Mercury derivatives. Try 2-3 with varying
sizes of additional groups - HgCl2, K2HgI4, PCMB, from the "Magic
seven" would be a good place to start.
Watch out for problems with your low pH, though. Some salts will form
insoluble hydroxide salts at pH 8.8. (HgCl2 & K2HgI4 should be okay)
Bart Hazes used to have an excellent set of notes online about heavy
atom derivatisation - I can't seem to find the URL right now...
HTH,
David
2009/7/15 Sebastiano Pasqualato <sebastiano.pasqual...@ifom-ieo-campus.it>:
Hi all,
I've got crystals of a protein of ca 200 residues, with 2 free cysteines, 5
histidines, 2 methionines.
We have nice diffraction for the native crystals, that grow in 150 mM KSCN,
17% PEG 3350, bis tris propane pH 8.8.
We are crystallising the SeMet derivative, but I'm not completely sure I
will be able to have nice crystals by saturday, when we have tunable time at
the ESRF.
I was thinking of trying with some heavy atom soaks, but only have like 30
crystals, so limited trials allowed!
Which compound would you advice as more likely to work, and thus worth
testing?
Thanks in advance for the suggestions,
ciao
s
--
Sebastiano Pasqualato, PhD
IFOM-IEO Campus
Dipartimento di Oncologia Sperimentale
Istituto Europeo di Oncologia
via Adamello, 16
20139 - Milano
Italy
tel +39 02 9437 5094
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Laurent Maveyraud laurent.maveyraud AT ipbs DOT fr
Université Paul Sabatier Toulouse III
I.P.B.S. UMR 5089 Groupe de Biophysique Structurale
Département Mécanismes Moléculaires des Infections Mycobactériennes
205 route de Narbonne 31077 TOULOUSE Cedex FRANCE
Tél: +33 (0)561 175 435 Fax : +33 (0)561 175 994
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