Garry,
One easy "test" you can do to determine whether it's devitrification would be to record electron diffraction patterns at the same time that you take pictures like the ones you showed us. If the ice is de-vitrify-ing, you should see a change in the diffraction pattern towards more ordered ice.
--
politics is more difficult than physics.
A. Einstein
David Gene Morgan
Electron Microscopy Center
047D Simon Hall
IU Bloomington
812 856 1457 (office)
812 856 3221 (3200)
http://iubemcenter.indiana.edu
________________________________________
From: 3dem <3dem-bounces at ncmir.ucsd.edu> on behalf of Garry P Morgan <Garry.Morgan at Colorado.EDU>
Sent: Wednesday, March 7, 2018 11:32 AM
To: 3dem at ncmir.ucsd.edu
Subject: Re: [3dem] 626 holder problems
thanks everyone for the helpful responses.
most opinions are that my second image shows a contamination buildup (although some think it’s de-vitrification). i’m hoping that getting the shutter assembly fixed & sealed properly fixes the issue. and it was apoferritin…as most of you probably guessed.
cheers,
Garry
On Mar 5, 2018, at 2:43 PM, Diaz-Avalos, Ruben <diazavalosr at janelia.hhmi.org> wrote:
> Hi Garry,
>
> I have seen something very similar to this before, and at that time, we concluded that it was heavy contamination from the rod assembly that operates the shutter on the holder. I sent the holder to repair and did not see the problem anymore.
>
> The sample looks like apoferritin.
>
> Ruben.
>
>> On Mar 5, 2018, at 4:22 PM, Garry P Morgan <Garry.Morgan at Colorado.EDU> wrote:
>>
>> Hello list!
>>
>> i have yet another round of questions regarding a problem with one of my Gatan 626 holders. i believe my holder tip is heating up, but i’m getting no indication of a temperature change on my control box. i have attached a couple images…first i would like to ask if anyone can acknowledge that the second image (named “5hours_in_TEM”) does in fact look like a de-vitrified sample.
>>
>> the first image is what my sample looked like initially, and after ~3 hours in the TEM; both images are from the same grid square. my nitrogen was topped up every 1-2 hours (so i’m confident that it didn’t run out), and when i noticed the change in the ice, i immediately checked the temperature with the control box and it was still at -184º (which is the usual reading for us). likewise, there was no unusual amount of drift during this transformation (as one might expect if the holder was running out of LN2). anyway, my main questions is: does anyone know what might be causing this? i’m almost certain something is not right in my holder, but i just got it back (for the second time), so i’m fairly confident all the o-rings as well as the clip spring are (or should be) new and in good shape.
>>
>> one possible clue: when i first put the rod into the TEM, the column vacuum would not recover until i opened the shutter, at which point the vacuum quickly started to improve. i guess this would indicate that the o-rings on the shutter assembly rod are not sealing completely…could this lead to a very slow/gradual warmup of the sample? later in my session, opening and closing the shutter had no impact on the column vac.
>>
>> any thoughts or possible solutions would be greatly appreciated. and just for fun….can anyone guess what this sample is?
>>
>> thanks,
>> Garry
>>
>>
>> <2hours_in_TEM.jpeg><5hours_in_TEM.jpeg>
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