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Re: [ccp4bb]: high solvent content?



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Hi Rui,

You don't mention whether you can index the low resolution data you can
see.  This might give you some indication of the actual solvent content.
 Also, is the protein glycosylated?  If so, perhaps you could try
cleaving the carbohydrates using PNGase F.  Other than that, I have
found the best way to attack this sort of problem is try as many
different cryoprotectants as possible.  Be creative.  I have found lots
of small organic molecules will serve as cryoprotectants (some better
than others).  Also, don't overlook tweaking the crystallization
conditions.  Just by modestly changing the pH or adding additional salts
you can dramatically alter the diffraction quality.  I would not
necessarily blame everything on high solvent content (which, as far as I
know, you cannot really alter once the crystal is grown).

Felix

Rui Zhao wrote:
> 
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> ***    CCP4 home page http://www.dl.ac.uk/CCP/CCP4/main.html    ***
> 
> Dear all,
>     I have some crystals of a protein complex (24kD + 14kD).  The sizes
> of the
> crystal are fine, but they diffract to 8-10A at their best (RT and
> cryo).  I notice that the crystals
> seem to have very high solvent content, since the crystals seem to be
> very soft
> and can even be damaged by loops.  I wonder if somebody can give me some
> 
> suggestions/comments that if the poor diffraction can be caused by the
> high
> solvent content or the intrinsic flexbility is likely to be the real
> cause?  If the high
> solvent content does contribute to the poor diffraction, did anybody
> have
> experience/tricks to overcome this problem?
>     Thank you very much for your help.                Rui.

-- 
*****************************************************************
Felix Vajdos                            ph.  650-225-6113
Postdoctoral Research Fellow            fax  650-225-3734
Department of Protein Engineering       e-mail vajdos@gene.com
Genentech, Inc.
1 DNA Way
South San Francisco, CA  94080
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