When the ACA meeting was in Hawaii (2006?), there was information about microwaving PEG solutions to artificially age new samples so that they would crystallize like the older PEG's. So I would infer that heat does have a significant effect on solid PEG's. All PEG's with MW >=600 are solids at room temperature. What I used to do was to make a large hot water bath (37-42C) and put the container of PEG in the bath so that it was 2/3 covered by water and let it melt. It would take 3-4 hours to fully melt the sample, but then you can make a 50-70% (v/v) solution that will remain liquid at room temperature for your crystallization.
Good Luck! Bryan -------------------------------------------------------------------------- Confidentiality Notice: This message is private and may contain confidential and proprietary information. If you have received this message in error, please notify us and remove it from your system and note that you must not copy, distribute or take any action in reliance on it. Any unauthorized use or disclosure of the contents of this message is not permitted and may be unlawful. -----Original Message----- From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of Flip Hoedemaeker Sent: Wednesday, June 23, 2010 6:26 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] PEG 1000 The meting point of PEG 1000 is around 38C. Obviously, if Sigma has heated the batch to fill the bottles in the first place this is a futile exercise... I'd ask them first. Flip Vellieux Frederic wrote: > R.Srinivasan wrote: >> Dear All, >> >> I have got initial crystals in a condition with PEG 1000. The >> PEG 1000 stock we had in our lab was rock solid and when i heated it >> to about 50 degrees for 15 to 20 minutes it became a solution. We >> thought the compound has got out dated or something like that and >> bought a brand new bottle from Sigma and this is rock solid too. >> >> Is this something characteristic of PEG1000? The hit condition >> says its 12.5% w/v PEG 1000 but it apparently seems i could never get >> a powder of it. >> >> So my question is, Can i go ahead using this melted solution >> form of PEG1000 for setting up optimizations? >> >> Thank you all in anticiaption, >> Vasan >> > All higher molecular weight PEG's are solid. Some are stored as flakes, > but as you mention some are rock solid. And it's very difficult to get > them out of the container (breaking the bottle is sometimes necessary). > > What I would go for personally would be mechanical grinding because I do > not know what happens to the PEG when it's heated to 50 deg or higher. > But perhaps you could take your bottle, cut the content in half, make a > powder out of the one half and use the other one with this heating > method and see if there are any differences. Or else if you happen to > have an analytical chemistry service at hand, provide them with a small > sample of each of the 2 and ask them to check if there is any difference. > > Fred. >
