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[ccp4bb]: SUMMARY: Hg compound

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Thanks to all the people that answered so quickly my question about the
solubilization of p-chloromercurybenzoic acid.

Briefly, four possibilities where proposed:

1. Use a different compound, p-chloromercuriphenyl-sulfonic acid, which is
more soluble.

2. Solubilise the Hg compound in a mother liquor type solution, containing
some hydrophobic compound (e.g PEG). It could be necessary to sonicate or
gently heat the sample to help solubilisation. This type of solution could
be used both to soak crystals, or to expose the protein to the heavy-atom
compound prior to crystallisation. For the latter, Louis Renault suggest
that:

> In this case small ratio of (protein/heavy-atoms) from 1/5 to 1/1 can be used. 
> It can work and improve occupancies when there is only a small number of binding 
> sites and preferentialy with small heavy-atom compound (HgCl for example) to 
> avoid non-isomorphous which can arise more frequently with this method.

3. Adjust the pH to basic.

4. Steve Ernst suggest to add a few crystals of the Hg compound directly to
the droplet and wait for the law of mass action making its work in a few
days.

I finally decided to follow the advice #3, which worked fine. I found all
the others interesting anyway, and I will certainly follow the advice from
Byron DeLaBarre and prepare all this heavy-atom solutions fresh.

Best wishes,

Miguel
--
Miguel Ortiz Lombardia              |      Siempre habrá nieve altanera 
Institut Pasteur                    |      que vista el monte de armiño
28, rue du Dr. Roux                 |      y agua humilde que trabaje
75724 Paris Cedex 15                |      en la rueda del molino.
Tel: +33-1 45 68 86 08              |      Y siempre habrá un sol también, 
Fax: +33-1 45 68 86 04              |      un sol verdugo y amigo,
email: ortiz@pasteur.fr             |      que trueque en llanto la nieve
------------------------------------|      y en nube el agua del rio.
http://www.pangea.org/ai-cat        |                     León Felipe