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Dear Chang,
What makes you think spots from salt crystals should not be as large?
You have got an ordinary small molecule crystal (or probably a
cluster of them) in the beam, with a unit cell somewhat bigger than
that of ice judging by the extra real ice rings you've got.
Hydrolysis of ATP and Mg2+ present - it's probably (Mg)3(PO4)2- it is
very unsoluble http://en.wikipedia.org/wiki/Solubility_table.
Best,
Tim
On 10/12/2012 09:29 AM, Chang Qing wrote:
> Hi, Thanks for answering my question. I think I'd better provide
> more informations. These four images were taken from one crystals.
> The distance of image1-2 is 250mm, and image3-4 is 100mm. I checked
> more than 10 crystals and results were similar. The spots look very
> large. The lowest resolution is about 6A. As my protein can
> hydrolyze ATP, so protein buffer with 5mM of ATP. There is 0.2M of
> MgCl2 in precipitant buffer with PH7.0. 0.06M of CsCl can improve
> quality of crystals. I also setup control, in which target protein
> was not added, and could get nothing in it. I don't think it is a
> protein crystal. But salt spot should not be so large. And the
> rings are not just ice-ring. As I got crystal first in hampton
> crystal screen kit with MgCl2, TrisHCl and PEG4,000, there are only
> rings in images from 5-6A to about 3A.
>
> 2012/10/12 THOMPSON Andrew
> <[log in to unmask]>:
>> Hi Chang No mention of the resolution limit / oscillation range
>> (I think I can see an ice ring, so I would guess 2.5 A?), but it
>> looks like salt to me, with some weaker satellite peaks that may
>> be something weird like an incommensurate phase. Did you try to
>> index? Cheers Andy ________________________________________ De :
>> CCP4 bulletin board [[log in to unmask]] de la part de Chang
>> Qing [[log in to unmask]] Date d'envoi : vendredi 12 octobre
>> 2012 08:11 À : [log in to unmask] Objet : [ccp4bb] Strange
>> diffraction image
>>
>> Hi, everyone:
>>
>> I just got some strange diffraction images from crystals with
>> triangular pyramid shape. I think this should not be protein
>> diffraction. I never saw so strange images like this. Does anyone
>> know what it is? Is it a kind of salt diffraction? Thank you very
>> much
>>
>> Chang
>
- --
- --
Dr Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen
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