You might also try to control the degree of oxidation using the microwave, and setting up trials after different numbers of cycles of heating.
Kendall
On Apr 12, 2011, at 12:41 PM, Jim Pflugrath wrote:
> Frances Jurnak published a paper in 1986 on PEG impurities and purification.
>
>
> As I recall, it turns out that different manufacturers put different
> additives in PEGs as preservatives. These are generally anti-oxidants.
> PEGs do get oxidized.
>
> I suggest you heat up your new PEG solutions to say 80 deg C and cool them
> down, then use them. Let us know what happens.
>
> -----Original Message-----
> From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of Jun
> Yong Ha
> Sent: Tuesday, April 12, 2011 6:57 AM
> To: [log in to unmask]
> Subject: [ccp4bb] Reproducing crystals.
>
> Hi all,
>
> Recently, I produced crystals with MBClass1-64 which contains PEG4000,
> HEPES-Na and NaCl. But, I struggled to reproduce crystals. I tried to set up
> tray with different batch of solution. I got the crystals only from 2008
> solution, but not from fresh ones. I asked technical service of Qiagen, but
> they did not have any stock.
>
> pH between fresh and old solution is the same. I could reproduce crystals
> with this old solution 100% when setting up.
>
> Do you have any experience like this? Is PEG4000 degraded or oxidized?
>
> Please help me.
>
> Thanks in advance.
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