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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