Re: [ccp4bb]: big crystals that diffrct poorly

[Allan Matte <allan@bri.nrc.ca>]

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Hi,

We have seen crystals like this several times. While I don't know of any
magic solutions (no pun intended), there are several things you can look
at or try. One might be post-crystallization soaking, using a higher [] of
precipitant to soak your crystals in or equillibrate over. Drawing solvent
out of your crystals may improve their order and increase their
resolution. Several papers on this have appeared in the last couple of
years in Acta Cryst. D and J. Cryst. Growth. Another would be to check you
crystals directly on SDS-PAGE or by MALDI-MS. The crystals have to be
carefully washed first, and dissolved in a suitable buffer. In the
case of one protein, we initally obtained large, poorly diffracting
crystals that contained both full-length protein and a major cleavage
product. Stabilizing the protein by adding protease inhibitors resulted in
a different crystal form that eventually led to the structure.

Allan

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| Allan Matte			    |	e-mail: Allan.Matte@BRI.NRC.CA |
| Macromolecular Structure Group    |	phone:   (514) 496-2557        |
| Biotechnology Research Institute  |   fax:     (514) 496-5143        |
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On Thu, 9 May 2002, Jay Pandit wrote:

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> 
> Hello all,
>  Everyone has probably experienced this - big (0.5mmx0.5mmx0.3mm),
> beautiful crystals (sharp edges, clean faces), that diffract strongly to
> 6A, and no further. What's the reason for this ? Are there any stories
> out there of tricks that have improved the resolution of such crystals ? 
> This is not a ccp4-related topic, but then this bb is the best general
> crystallography discussion group that there is, so I have to post this
> question here ... 
>  Jay
> -- 
>  Jay Pandit
>  MS 4039
>  Pfizer Global Research and Development         Phone:  (1) 860 441 3738
>  Eastern Point Road                             Fax  :  (1) 860 686 2095
>  Groton CT 06340 , USA                          email: pandit@pfizer.com
>