Choice of heavy atom derivatives

From: Federica Basilico
Date: 11 January 2012 11:23


Hi everyone,

I have crystals of a protein of 176 residues, with 5 Cys, 8 His, 3 Met.
Native crystals grow in 10% MPD, 100mM Bicine pH 9.0. They show a nice diffraction, but appear to be perfectly twinned.
I have crystallised a SeMet derivative, but I have not been able to collect sufficiently good data, to get the phases.
Thus, I was thinking of trying with some heavy atom soaks.
Given the characteristics of my protein and crystallisation conditions, which compounds and conditions would you advice as worth testing?
I am a beginner in crystallography, so all your suggestions would be precious to me...
Thanks in advance,

Federica

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Federica Basilico

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From: Miguel Ortiz Lombardía

Le 11/01/12 12:23, Federica Basilico a écrit :

Hi,

This site may help:

http://hatodas.harima.riken.go.jp/

--
Miguel
http://www.afmb.univ-mrs.fr/Miguel-Ortiz-Lombardia

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From: Francis E Reyes


In most cases, structures can be solved (and biological questions answered) in twinned cases. I wouldn't be discouraged.
What is 'good' data to you? What are you considering as 'bad' data?
You've come to the right place. Seek advice from people who have solved structures within the last 5 years using modern software. You'd be surprised how good the software for structure solution/refinement is these days.
This by chance is not a  metalloprotein is it? No covalently bound heavy metals? (maybe you have done some biochemistry and found some heavy metal requirement for activity, purification, etc)
If your native crystals diffract well on a home source, I would try soaking a fresh 500 mM solution of KI (iodide) for 5-10 seconds and collect the anomalous signal at home. If it kills your crystals, move to more toxic things...

>
> Thanks in advance,
>
> Federica
>

Cheers,

F

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Francis E. Reyes