Hi Everyone,
Just to put a word in favour of the re-usable bases. We've been using
them for many years with little issue. The advantage of being able to
make up "emergency" loops when needed during a freezing session being
a big advantage.
I have occasionally noticed the slipping pin issue (and when it occurs
that base is withdrawn from use), but I've not noticed a general
problem with smaller movement upon rotation. However, we do see the
ice on the base issue (mainly due to impatient users freezing their
samples). Here, samples can be seen to shift, even without rotation,
for a few moments after mounting. Once the ice on the base/goniometer
inteface has melted, the position stabilises.
Of course, one advantage of the Diamond Light Source microfocus
beamline, I24, is that the pin is vertical in the beam, so the mount
isn't fighting gravity during rotation.
Andy
Quoting Diana Tomchick <diana.tomch...@utsouthwestern.edu>:
We no longer use the reusable bases for the same reasons, but we do
re-use our bases. If you use superglue to glue the pins into the
bases, you can remove the pins from the bases by soaking them in
acetone. This works about 75% of the time, especially if you are
careful not to use too much superglue when you glue the pin into the
base.
It goes without saying that the use of acetone will dissolve the
loop, but then the main reason we remove the pin is due to
imperfections in the loop, so no big deal.
Whenever we see the motions that you describe, we postulate that
somehow the pins were damaged and they are loose in the base.
Occasionally this motion is ascribed to ice between the base of the
pin and the magnetic mount, but this happens very rarely in our
experience.
Diana
**************************************************
Diana R. Tomchick
Professor
Departments of Biophysics and Biochemistry
UT Southwestern Medical Center
5323 Harry Hines Blvd.
Rm. ND10.214A
Dallas, TX 75390-8816
diana.tomch...@utsouthwestern.edu
(214) 645-6383 (phone)
(214) 645-6353 (fax)
________________________________
From: CCP4 bulletin board <CCP4BB@JISCMAIL.AC.UK> on behalf of
Tao-Hsin Chang <taohsin.ch...@gmail.com>
Sent: Sunday, November 15, 2020 3:07 PM
To: CCP4BB@JISCMAIL.AC.UK <CCP4BB@JISCMAIL.AC.UK>
Subject: Re: [ccp4bb] Stabilizing Mitegen reusable bases/mounts
EXTERNAL MAIL
Hi Patrick,
I have met the same issue and that is very bad for any micro-focus
beam and small crystals. I have talked with Mitegen and they are
developing a new type of reusable base having an improvement for
this issue. You may get some update from them. But, I do not use the
reusable bases anymore.
Best wishes,
Tao-Hsin
On Nov 15, 2020, at 3:45 PM, Patrick Loll
<pjl...@gmail.com<mailto:pjl...@gmail.com>> wrote:
Hi everyone,
I’ve become very fond of the Mitegen reusable bases for mounting
crystals, since the reusable aspect savse me from having to discard
the base every time I break a microloop. However, once the crystals
arrive at the synchroteon, I observe motions of the loops (some
gradual, some sporadic). The the amplitudes of these motions are
becoming significant as I take data from smaller and smaller
crystals. I don’t think I’m imagining this, since the good folks at
NSLS-2/AMX have warned me about this very issue.
I’m writing to ask if anyone has any clever ideas about stabilizing
these assemblies. Obviously, I can epoxy the pins in place, but then
I’ll probably need to discard the entire assembly when I break a
loop, and I’d prefer not to waste more money than necessary. I’ve
considered putting a bead of wax at the point where the pin enters
the base (although I haven’t yet checked to see if that will survive
immersion in liquid nitrogen). Does anyone have any other (better)
ideas?
Much obliged in advance,
Pat
__________________________
Patrick J. Loll, PhD
Professor of Biochemistry & Molecular Biology
Drexel University College of Medicine
Room 10-102 New College Building
245 N. 15th St.
Philadelphia, PA 19102-1192 USA
(215) 762-7706
pj...@drexel.edu<mailto:pj...@drexel.edu>
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