Dear Nazia Nasir,
did you warm up the solution a little? This makes working with PEG
solutions a lot easier. You may also note the Hampton do not maintain
the pH: they use the buffers as indicated but this does not mean that
the final solution still has pH 6.5. With your ingredients it probably
is, but e.g. with high concentrations of imidazole the final pH would
differ a lot.
Best,
Tim
On 12/06/2013 02:37 PM, Nazia Nasir Phd2009,ProteinCrystall.Lab wrote:
> I have obtained crystals in Hampton Crustal Screen 2, condition 26.The
> condition has the following components:
> 1. 0.2 M ammonium sulphate
> 2. 0.1 M MES buffer pH 6.5
> 3. 30% PEG mononmethyl ether 5,000.
>
> When I try to prepare the screen in-house, I use the Hampton stocks of 3.5
> M ammonium sulphate and 50% PEG mononmethyl ether 5,000. I make the MES
> buffer using MES hydrate, SigmaUltra from Sigma and maintain the pH
> accurately. The water I use is filtered MilliQ. However, the PEG MME and
> the rest of the solution remains immiscible and thus, forms droplets of
> separated PEG when I set up crystallization. The original condition from
> Hampton has no such problems and gives good crystals.
>
> Can anyone let me know how to overcome the problem insolubility of PEG MME
> in the buffer mix? I have not faced such problems with other conditions
> which I prepare in house and have PEG in them. Further, it's not possible
> for me to use the original screen all the time.
>
> Thanks a lot!
>
>
> Regards
>
--
Dr Tim Gruene
Institut fuer anorganische Chemie
Tammannstr. 4
D-37077 Goettingen
GPG Key ID = A46BEE1A
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