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Re: [ccp4bb] Fwd: [ccp4bb] crystallisation and mosaicity |
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CCP4bb navigationCCP4bb <-- 2008 <-- June 2008 <-- 06 June 2008Subject: Re: Fwd: crystallisation and mosaicity From: "R {- dot -} M {- dot -} Garavito" garavito {- at -} MSU {- dot -} EDU Date: 2008-06-06 The question has been asked and answered not by protein crystallography, but by cyroelectron microscopy and EM freeze etch research. Even as far back as the early 1960's, people noticed that liq. N2 was really slow at cooling. Read the cyroEM work on the bacteriorhodopsin photocycle and check out the wicked guillotine device for freezing. The slower freezing in liq. N2 is partly due to nitrogen's low heat capacity, which can be seen in the fact that there is only about a 13 degree difference between the freezing and boiling points of N2 (~64K vs. ~77K). In contrast, difference between the freezing and boiling points for propane is almost 148 degrees (~83K vs. ~231K). Thus, it makes sense to freeze in liq. propane, but then shift to liq. N2 for storage and shipping. Making propane popsicles for storage, shipping, and mounting is not necessary. Michael **************************************************************** R. Michael Garavito, Ph.D. Professor of Biochemistry & Molecular Biology 513 Biochemistry Bldg. Michigan State University East Lansing, MI 48824-1319 Office: (517) 355-9724 Lab: (517) 353-9125 FAX: (517) 353-9334 Email: garavito@msu.edu **************************************************************** On Jun 5, 2008, at 5:11 PM, Tommi Kajander wrote: > according to literature,see below and references > http://www.px.nsls.bnl.gov/courses/papers/ZD_EG_papers.html, > it is not clear that liq. propane plunged item would cool > faster. (whilst i havent tested this)... > > Would anyone have actual experimental data with protein crystals > on the hyperquenching suggested by > Warkentin, V. Berejnov, and R. E. Thorne, J. Appl. Cryst. (2006) 39, > 805-811. (no diffraction data in the paper). in particular with > small samples. > > thanks, > Tommi > > Quoting Petr Leiman > >>>> yes you are right, but I assumed if people see a cloud of condensed >>>> fog over their LN2 bath they should remove that by >>>> a) filling up the bowl completely e.g. some LN2 drips out of the >>>> bowl >>>> b) blow the fog away before you dip >> >> I think the original poster meant the relatively low heat >> conduction of >> liquid N2, which causes boiling around the crystal immediately after >> plunging. >> >> The best way to freeze things is to put a small container of liquid >> ethane >> or propane into a liquid N2 bowl, and plunge into the ethane/propane >> (this >> methods was suggested earlier). >> >> Petr >> >> > > > -- > Tommi Kajander, Ph.D. > Macromolecular X-ray Crystallography > Research Program in Structural Biology and Biophysics > Institute of Biotechnology > P.O. Box 65 (Street address: Viikinkaari 1, 4th floor) > University of Helsinki > FIN-00014 Helsinki, Finland > Tel. +358-9-191 58903 > Fax +358-9-191 59940 > CCP4bb navigationCCP4bb <-- 2008 <-- June 2008 <-- 06 June 2008 |
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