Matthew,
I have not had any problem with our Cryojet XL (90 - 300 Kelvin), it is
very stable at sub-zero temperatures, I checked it over a longer period
using a highly sensitive electronic device. Also, you can buy the
Cryojet HT that can be operated from 90 – 490 Kelvin!
The heaters will be okay for both devices.
But more important, coaxial mounting does not help unless the capillary
is really short! If the capillary is to long, water will again collect
at the point closest to the nozzle, especially if the data collection
takes more than one or two hours!
I am not aware of any cheaper devices that deliver a stable temperature
over a prolonged time-span.
- J. -
[EMAIL PROTECTED] wrote:
Hi Patrick -
Many cryosystems (definitely the Cryojet, and I believe the Cryostream) can
be set to run at any temperature between room temp and liquid nitrogen
temp. I'm not sure of the temperature stability at temps > 0 C, and you
might burn out the heaters prematurely if you do this all the time, but it
should work. Then you just need to move the nozzle so it's coaxial with
your goniostat's rotation axis, and aim the capillary down the nozzle. You
could probably even move the capillary *inside* the cryo nozzle a bit, so
only the bit with the crystal is in the free stream.
It's not a cheap solution, but you've almost certainly got a cryosystem
already...
- Matt
--
Matthew Franklin , Ph.D.
Senior Scientist, ImClone Systems
180 Varick Street, 6th floor
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CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK> wrote on 07/10/2007 02:07:37
PM:
Jeroen brings up a good point. Back in the old days, around 5 B. C.
(Before Cryo), we would use a chilled air generator to blow a stream
of cold air along the capillary axis to keep the crystals just above
their freezing point--it made a huge difference in crystal lifetime.
I recall a colleague devising an apparatus from a 50 ml conical
tube. The bottom was cut off and cold air was blown in from the
other end. Windows were cut in either side to allow the beam to pass
& covered in mylar. This way the entire capillary was contained
within the cold tube, so no temperature gradients formed along the
length of the capillary (temp gradient => distillation => dead
crystal). Later, we purchased a very clever goniometer head from
Nonius that had a plastic cylinder attached to goniometer head, with
a swivel, so the hose supplying cold air didn't get tangled during
data collection...
I've often thought duplicating this apparatus when we encounter cryo
problems, but I'm always stymied when trying to find a cheap and
simple source of cold air. Any bright ideas?
--
Jeroen Raymundus Mesters, Ph.D.
Institut fuer Biochemie, Universitaet zu Luebeck
Zentrum fuer Medizinische Struktur und Zellbiologie
Ratzeburger Allee 160, D-23538 Luebeck
Tel: +49-451-5004070, Fax: +49-451-5004068
E-mail: [EMAIL PROTECTED]
Http://www.biochem.uni-luebeck.de
Http://www.iobcr.org
Http://www.opticryst.org
--
If you can look into the seeds of time and say
which grain will grow and which will not - speak then to me (Macbeth)
--
