does anybody have a reference for that paper (or was it a poster?) by robert thorne on systematic investigations about the cooling process? are there similar studies with propane? isn't propane a pain for transporting samples because of the regulations? regards, jose ==================================== Systems Biology Talks at Diamond (SR User Meeting 2007) http://systemsbiology07.wordpress.com/ <https://outlook.rl.ac.uk/exchweb/bin/redir.asp?URL=http://systemsbiology07.wordpress.com/> ==================================== Jose Ribeiro Brandao-Neto, MPhil Beamline Scientist - I04-1 Macromolecular Crystallography Group Diamond Light Source Ltd Diamond House DR1.78 Harwell Science and Innovation Campus RAL, Chilton, Didcot Oxfordshire OX11 0DE United Kingdom tel: +44 (0)1235 778506 +44 (0)1235 778000 fax: +44 (0)1235 778448 [EMAIL PROTECTED] http://www.diamond.ac.uk <https://outlook.rl.ac.uk/exchweb/bin/redir.asp?URL=http://www.diamond.ac.uk/> ====================================
________________________________ From: CCP4 bulletin board on behalf of Jim Pflugrath Sent: Fri 06/06/2008 19:24 To: [email protected] Subject: Re: [ccp4bb] cryo-cooling, was: Re: [ccp4bb] crystallisation and mosaicity > Jim, > > The fact that liquid propane can exist at a range of temperatures is actually > a MAJOR advantage. While you must ensure that the temperature of the liquid > propane is just above its own freezing point, the very high boiling point of > propane ensures that there is liquid-to-solid contact with your sample for > good heat transfer. When the cryogen boils, there is a gas-to-solid contact, > slower cooling, and a greater chance of ice crystal formation. >.... Yes, I agree with the theory, but I also I believe that if you quickly plunge your crystal into liquid nitrogen, that the high velocity through the liquid presents fresh liquid nitrogen as you go and the gas-to-solid contact is neglible. I think speed and having no cold-gas-layer above the liquid cryogen are the main points of the Warkentin et al. paper cited previously. I have observed many slow people freezing crystals instead of flash-cooling them. But for some crystals flash-cooling is better at temperatures higher than in the 77 K to 100 K regime for unknown reasons. This can be one reason why flash-cooling in the gas stream occassionally is better. It is also why liquid propane worked for Raji E. and Karolin L.: they were using a temperature above the freezing point of propane. If you are having problems with flash-cooling, go ahead and try propane (my preference is CF4 over propane though). And a trick we learned from the University of Cambridge is to fill a balloon with the gas, put the balloon opening over a 15 ml Falcon tube and then condense/freeze the gas in the tube for pouring into vials later. This prevents wasting gas by bubbling through a coil held in liquid nitrogen. This is just one of techniques described in the PDF I mentioned. It is also not a bad idea to practice flash-cooling on lysozyme or thaumatin crystals and get good at it before working with your own precious crystals. Jim <DIV><FONT size="1" color="gray">This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom </FONT></DIV>
