[3dem] "leopard skin" ice

[Stefan Bohn]

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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>
>
>
> --
> Paul Chipman
> Assistant Director of Research
> Biochemistry and Molecular Biology
> University of Florida
> 352-294-1790
>
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-- 
Dr. Stefan Bohn
Department of Cellular and Molecular Pharmacology
University of California
1700 4th Street, Box 2530
San Francisco, CA. 94158

Phone: +1 (415) 476 - 2980
Fax: +1 (415) 514 - 9736
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