[3dem] "leopard skin" ice

[Bob Grassucci]

After closer examination of the image I do recall seeing this 
type of ice on part of the grid after we had been collecting 
on our Polara for 2 weeks.  It was interesting because it was 
present near the grid bars (where it was coldest) and absent.
Towards the center of the grid it was absent.  I vote for the term
Turtle ice:)
Bob

Sent from Bob's iPhone

> On Nov 21, 2013, at 6:36 PM, Montserrat Samso/FS/VCU <msamso at vcu.edu> wrote:
> 
> 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" (fromSchildkroete = plate toad).
> 
> Hope thathelps,
> 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
>>> 
>>> <alligator_ice.tif> _______________________________________________
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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
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