Hi Sebastiano,
In addition to the heavy atom database server and the suggestions made
here, you could try the strategy described in this paper:
Lott JS et al. (2003) Acta Cryst D Biol Crystallogr, Dec (Pt 12):
2242-6. Making the most of two crystals: structural analysis of a
conserved hypothetical protein using native gel screening and SAD
phasing.
I second the sulfur SAD suggestion made earlier. 2 Met and 2Cys for a
200 residue protein would be doable. You can collect at 1.9 Å
wavelength to enhance the signal.
Best,
Sarma
On Jul 15, 2009, at 6:37 AM Jul 15, 2009, Savvas Savvides wrote:
Hi Sebastiano,
Given that your crystallization condition contains KSCN, I would
certainly
give Hg(SCN)2 a go among other Hg options for a protein containing
free
cysteines. Hg(SCN)2 might end up being more compatible with your
crystal
form, and might thus minimize non-isomorphism issues.
Best of luck
Savvas
-----Original Message-----
From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf
Of David
Briggs
Sent: Wednesday, July 15, 2009 3:27 PM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] heavy atom derivative choice
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
--
============================
David C. Briggs PhD
Father & Crystallographer
http://drdavidcbriggs.googlepages.com/home
Skype: DocDCB
============================
E-mail message checked by Spyware Doctor (6.0.1.441)
Database version: 6.12830
http://www.pctools.com/en/spyware-doctor-antivirus/
