I would go along with Harry & friends, I used crystal cooling when I was at Aafje Vos' Struktuurchemie lab in Groningen in 1972, when the technique had already been in routine use there for at least 10 years, in order to study compounds that are liquid at ambient temp (of course it was custom-built kit using a collection of liq N2 Dewar vessel & tubes, nothing as fancy as a Cryostream!). The Groningen group really pioneered the use of low temp for small molecule structures and I don't recall increased mosaicity ever being an issue. Occasionally you would get a compound with a phase transition on the way down and the crystal would literally explode in a puff of powder before your eyes! The motive for using low temp was of course to reduce the thermal motion and libration effects, and thus greatly improve the accuracy of the molecular geometry, and low temp is pretty well essential if you're into valence density deformation maps, again in order the minimise the contribution from thermal motion.
-- Ian > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of harry powell > Sent: 19 June 2008 14:05 > To: Remy Loris > Cc: CCP4BB@JISCMAIL.AC.UK > Subject: Re: [ccp4bb] is it Ok to freeze > > Hi > > Without wishing to start an argument, I've been checking with > some of my colleagues who are chemical crystallographers - > the reply I get is that, for routine structural analysis, > "pretty well all datasets are collected at 100K unless the > crystals fall apart at low T, or if the cryostream is broken". > > I should point out that the first production Cryostream that > I came across (serial number 2, which I think may have been > the first one sold!) was in the Cambridge Department of > Chemistry in about 1985. They didn't become common until the > mid-1990's in PX labs, when they were already > well-established as a bit of pretty well essential kit for > small molecule work. > > So although what Remy says is true, the practice is to > cryocool most of the time. > > > On 19 Jun 2008, at 12:08, Remy Loris wrote: > > > Typically crystals of small organic compounds do not > require freezing as there are no solvent channels. They do in > general not suffer from radiation damage at room temperature > the way protein crystals do. Occasionally they are mounted in > a capillary instead of simply glueing them to a goniometer if > they are air sensitive. In principle freezing should not > damage the crystals, but one still may have to be carefull if > the crystals are large. I think you risk increasing > mosiacity, and any manipulation that is not needed will on > average only reduce the quality of the specimen rather than improve it > > Remy Loris > Vrije Univesiteit Brussel > > Jayashankar wrote: > > Dear Scientists and Friends, > I am not sure, whether organic crystals need > to be in cryo stream necessarily during data collection from > an in house > xray machine . > How most of the organic crystals have been > solved mostly? > -- > S.Jayashankar > (A bit confused new generation researcher). > Research Student > Institute for Biophysical Chemistry > Hannover Medical School > Germany > > > Harry > -- > Dr Harry Powell, MRC Laboratory of Molecular Biology, MRC > Centre, Hills Road, Cambridge, CB2 2QH > > > > > Disclaimer This communication is confidential and may contain privileged information intended solely for the named addressee(s). It may not be used or disclosed except for the purpose for which it has been sent. If you are not the intended recipient you must not review, use, disclose, copy, distribute or take any action in reliance upon it. If you have received this communication in error, please notify Astex Therapeutics Ltd by emailing [EMAIL PROTECTED] and destroy all copies of the message and any attached documents. Astex Therapeutics Ltd monitors, controls and protects all its messaging traffic in compliance with its corporate email policy. The Company accepts no liability or responsibility for any onward transmission or use of emails and attachments having left the Astex Therapeutics domain. Unless expressly stated, opinions in this message are those of the individual sender and not of Astex Therapeutics Ltd. The recipient should check this email and any attachments for the presence of computer viruses. Astex Therapeutics Ltd accepts no liability for damage caused by any virus transmitted by this email. E-mail is susceptible to data corruption, interception, unauthorized amendment, and tampering, Astex Therapeutics Ltd only send and receive e-mails on the basis that the Company is not liable for any such alteration or any consequences thereof. Astex Therapeutics Ltd., Registered in England at 436 Cambridge Science Park, Cambridge CB4 0QA under number 3751674
