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:CCP4BB@JISCMAIL.AC.UK] On Behalf Of Jun Yong Ha Sent: Tuesday, April 12, 2011 6:57 AM To: CCP4BB@JISCMAIL.AC.UK 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.
