How low? Back in the old days when we mounted xtals in capillaries, you could sometimes see significant reduction in radiation damage by data collection temperature from room temp to ca. 0 deg C (zero is generally safe, since the PEGS/salts in your mother liquor will depress the freezing point). In this case, it's critical that you bathe the entire capillary in a stream of cool air; if you just aim the cold stream at the part of the capillary containing the crystal, you'll get all sorts of nasty temperature gradients, leading to distillation of components from the mother liquor and slow painful death for the crystal (OK, sometimes not so slow). We used to fashion cylinders that enclosed the capillary on all sides and extended the entire length of the capillary, and blew the cool air through these cylinders (cheap/easy way to do this was to cut the end off a 15 ml conical tube, then cut two windows at the position of the crystal (opposite one another, 180 deg apart), and tape mylar over the windows. This way you have an approximately air-tight cylinder, but don't put a lot of scattering material in the beam.
I seem to have heard reports of people flash-cooling in capillaries, but I'm not sure where to find details. Pat On 17 Feb 2011, at 12:03 PM, R Conners, Biochemistry wrote: > Dear all, > > We are working on a Category 3 protein which must be contained so we have our > crystals mounted in a loop and then covered with a plastic Mitegen cover > which is glued in place. We're currently collecting at room temperature, but > wondered if anyone has any experience of using a contained system at low > temperatures? Any attempts I've had so far at freezing through either the > plastic or a glass capillary have resulted in formation of ice on the surface > so it is not even possible to see the crystal to centre it. > > Best wishes, > > Becky > > ------------------------------------------------- > Dr Becky Conners > School of Biochemistry > University of Bristol, UK > > http://www.bris.ac.uk/biochemistry/brady > r.conn...@bristol.ac.uk > 0117 3312149 --------------------------------------------------------------------------------------- Patrick J. Loll, Ph. D. Professor of Biochemistry & Molecular Biology Director, Biochemistry Graduate Program Drexel University College of Medicine Room 10-102 New College Building 245 N. 15th St., Mailstop 497 Philadelphia, PA 19102-1192 USA (215) 762-7706 pat.l...@drexelmed.edu
