Although many of you may already use this technique, a more obvious, cheaper and easier method is to just leave the cryovial (or puck) in the liquid nitrogen while mounting your crystal. Once mounted, raise the vial out of the dewar (slightly above the mouth of the dewar where the cooled gas is) and plunge the crystal directly into the vial filled with liquid nitrogen. Then quickly replace the vial to the dewar. This avoids the gas layer and also reduces unnecessary pin manipulation!
Kris ------------ Kris F. Tesh, Ph D Director, Macromolecular Products Rigaku Americas Corporation 9009 New Trails Drive The Woodlands, TX 77381 USA 001 281 362 2300 x 144 -----Original Message----- From: CCP4 bulletin board [mailto:[EMAIL PROTECTED] On Behalf Of James Stroud Sent: Thursday, February 01, 2007 5:06 AM To: CCP4BB@JISCMAIL.AC.UK Subject: Re: [ccp4bb] Removal of cold gas layer for cryocooling I propose a simple contraption to minimize the vapor layer in cryocrystallography, using freezing in the liquid phase. This idea is based on the findings in the citation below. It is modified from designs used in the pet feeding industry. The novel aspect is that liquid nitrogen is used rather than water or nutritional liquids and that this particular contraption can be used for the freezing of crystals rather than the satiation of animals. The idea is to invert a dewar over a dish. The dewar sits on a block to raise its opening while the block has a gap to allow liquid N2 to escape from the dewar. The block is adjusted so that the opening to the dewar is just below the brim of the dish, minimizing the vapor head space. The cold vapor should either rise or fall depending on its density relative to the atmosphere, minimizing the thickness of the trapped vapor phase. The dish should be deep enough to allow one to plunge a crystal in the liquid N2 without easily hitting the bottom of the dish. I call this invention "James's Petfeeder Contraption for Cryocrystallography". A diagram is at: http://www.jamesstroud.com/Contraptions/Petfeeder.pdf James On Feb 1, 2007, at 12:52 AM, Florian Brückner wrote: > Dear everyone, > > has anyone tried removing the cold gas layer above liquid nitrogen > (or propane) by blowing or sucking to improve cooling rates in the > cryocooling of crystals. I would like to try and I would be happy > if someone could share some experience. > > Florian. > > P.S.: there is an interesting paper: J. Appl. Cryst. (2006). 39, > 805-811. > > -- > ---------------------------------------------------------------------- > --------------- > > Florian Brueckner > AG Cramer > Gene Center > Feodor-Lynen-Str. 25 > D-81377 Muenchen > Germany > > Fon: +49 89 2180-76955 > Fax: +49 89 2180-76999
