Dear Tim,
you are right that 150mM NaCl is 'stronger' than 2.5% PEG. If you
calculate the relative humidity difference between 150 and 300mM Nacl
you get 99.5 vs 98.9% whereas the difference between 5 and 2.5% P8K is
99.96 vs 99.99% ie virtually nothing. You can calculate these values
here: http://go.esrf.eu/RH.
Cheers, Matt.
On 2014-05-02 13:56, Tim Gruene wrote:
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> Dear Maria,
>
> this is similar to the condition I used for my PhD thesis. I suppose
> the following happens:
>
> when you mix the drop the protein crystallises by inverse salting-in
> because you dilute the high-salt concentration. This happens
> instantaneously and you are lucky enough to observe crystals.
>
> As you leave the drop overnight you are observing the opposite from
> what normally happens: your drop gets larger instead of smaller
> because the hygroscopy of the 150mM NaCl is stronger than that of
> 2.5%
> PEG8K and you further dilute the drop so that the crystal disappears.
>
> Check if your drops get bigger overnight to check if my assumption is
> correct.
>
> During my PhD I worked with 0.5M NaCl and maybe I am wrong that 150mM
> NaCl is stronger than 2.5% PEG8k.
>
> Best,
> Tim
>
> On 05/02/2014 01:39 PM, dusky dew wrote:
>> Dear All,
>>
>> I am trying to crystallize a protein with Adenosine. My protein is
>> in 20 mM Tris, 300 mM NaCl and the crystals appear in a condition
>> with 5 percent PEG8K, 0.1 M Sodium Cacodylate. The protein is
>> incubated with adenosine for 1/2 hr before setting the drop. The
>> crystals appear right after the drop is set but unfortunately they
>> dissolve overnight. The plate is kept at 16 degree.
>>
>> Could anyone elaborate on this. Is it possibly occurring because
>> Adenosine has stability issues.
>>
>> Thanks for your suggestions. ~ Maria
>>
>
> - --
> - --
> Dr Tim Gruene
> Institut fuer anorganische Chemie
> Tammannstr. 4
> D-37077 Goettingen
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--
Matthew Bowler
Synchrotron Science Group
European Molecular Biology Laboratory
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