[3dem] "leopard skin" ice

Thu Nov 21 15:36:38 PST 2013

Hi,

We saw similar contamination and realized that translating the cryo-holder a "long" distance resulted in rapid contamination buildup. Then we checked the o-ring of the cryo-holder and realized that there was a little too much vacuum grease. Removing the excess vacuum grease solved the problem in the subsequent cryoEM sessions.

Hope this helps,

Montserrat 

Montserrat Samso, Ph.D.
Assistant Professor
Dept. Physiology and Biophysics
Virginia Commonwealth University
1101 E. Marshall St., RM 3-009
Richmond VA 23298
Tel: 804-828-8728
Fax: 804-828-9492
Email: msamso at vcu.edu

-----3dem-bounces at ncmir.ucsd.edu wrote: -----
To: "3dem at ncmir.ucsd.edu" <3dem at ncmir.ucsd.edu>
From: "Stefan Bohn" 
Sent by: 3dem-bounces at ncmir.ucsd.edu
Date: 11/21/2013 06:24PM
Subject: Re: [3dem] "leopard skin" ice

Hi,

sometimes this ice was appearing, when the ethane bottle was nearly empty. Sometimes, ethane bottle was full and it still appeared (open plunger, F20, identical(!) sample - 20mM Hepes, 20mM NaCl, 10mM MgCl2, ~15% glycerol) - in those instances I attributed it to not having filled the nitrogen high enough in the dewar, maybe not cooling the ethane long enough. Sometimes only part of the grid showed this ice, other parts were normal - particles were distributed evenly on those grids.

But, in general, it was not reproducible. I couldn't correlate it to the phase of the moon, as was suggested to me several times...

Most importantly, we referred to it as "turtle-ice" (from Schildkroete = plate toad).

Hope that helps,
Stefan.

On Thu, Nov 21, 2013 at 1:26 PM, Jacob Brink <jbrink at jeol.com> wrote:
Hi Paul and Frank,

We've also seen this type of ice in Flu particle preps at NIBSC during the cryo-EM course, but we'd see it in the middle of the ice, away from particles (see below). The ethane tank had not been moved. So, we never really could attribute it to anything unless the ice would get really thin? Open air plunger (!) and imaged in a 2100-LaB6 TT.

Jaap

On Nov 21, 2013, at 2:36 PM, Paul Chipman <pchipman at ufl.edu> wrote:

Hi Frank,

At Purdue we called this "alligator ice" and would see it from time to time, occasionally when an ethane tank was nearing empty.  As such we attributed to impurities that impeded freezing.  It could also be just something in the buffer or sample that alters the freezing.  The recent image below displays this type of ice but only near the viral particles.  Most of the ice was great except in areas of high particle concentration.  When I told the student the name we gave this type of ice, I got a laugh.

Go Gators! (Florida)

Cheers,
Paul 

On Wed, Nov 20, 2013 at 1:54 AM, <frankpolzer at physik.hu-berlin.de> wrote:
Dear all,

During the last weeks, I frequently observe what I believe is so-called
leopard skin ice in my vitrified samples (plunge frozen in ethane using
Mark IV Vitrobot).

What again is the reason for this type of ice and how can this be avoided?

Thanks for your help in advance,

Frank

Dr. Frank Polzer

TEM Group
Insitute of Physics
Humboldt Universität zu Berlin
Newtonstraße 15
12489 - Berlin
Tel.: +49 30 2093-4995 (office)
Tel.: +49 30 2093-7829 (TEM)
Fax: +49 30 2093-7886

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Assistant Director of Research
Biochemistry and Molecular Biology
University of Florida
352-294-1790

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Dr. Stefan Bohn
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