[ccp4bb] PEG 1000
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
Re: [ccp4bb] PEG 1000
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.
Re: [ccp4bb] PEG 1000
On Wed, Jun 23, 2010 at 12:40:35PM +0530, 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? Since mass is temperature independent you can use the PEG1000 solution to weight 50mg and dissolve it in 50-80ml water, let it cool down to room temperature and top it up to 100ml (with water). I think this way you created a 50% w/v stock solution of PEG1000 which you can further dilute to set up the desired concentration. Tim Thank you all in anticiaption, Vasan -- -- Tim Gruene Institut fuer anorganische Chemie Tammannstr. 4 D-37077 Goettingen GPG Key ID = A46BEE1A signature.asc Description: Digital signature
Re: [ccp4bb] PEG 1000
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.
Re: [ccp4bb] PEG 1000
Actually it probably would be better ask the supplier of your screen first how they got PEG 1K diluted to 12.5%. If they did hit it then you have to do the same. But even better idea is to order that PEG 1K from the same company that sells the screens. It will insure identical treatment. My 2 cents. Vaheh From: CCP4 bulletin board [mailto:ccp...@jiscmail.ac.uk] On Behalf Of R.Srinivasan Sent: Wednesday, June 23, 2010 3:11 AM To: CCP4BB@JISCMAIL.AC.UK Subject: [ccp4bb] PEG 1000 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 To the extent this electronic communication or any of its attachments contain information that is not in the public domain, such information is considered by MedImmune to be confidential and proprietary. This communication is expected to be read and/or used only by the individual(s) for whom it is intended. If you have received this electronic communication in error, please reply to the sender advising of the error in transmission and delete the original message and any accompanying documents from your system immediately, without copying, reviewing or otherwise using them for any purpose. Thank you for your cooperation.
