[3dem] contamination in cryo samples

[Schwartz, Cindi (NIH/NIAID) [C]]

I would echo having very dry nitrogen when you load samples. We built a simple way of drying dewars overnight. We hung them upside down and shoved a hose that went to the house air in there. Turn on the house air and voila! Dry dewars. We put an industrial air filter in the system to make sure we weren't blowing any contaminants into the dewars. They were nice and dry every morning.

Good luck!

--
Cindi L. Schwartz
Electron Microscopist
Rocky Mountain Labs/NIAID/NIH
903 South 4th Street
Hamilton, MT  59840
240-669-5473
Cindi.Schwartz at NIH.gov<mailto:Cindi.Schwartz at NIH.gov>
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From: Nadav Elad <nadav.elad at weizmann.ac.il<mailto:nadav.elad at weizmann.ac.il>>
Date: Thursday, September 1, 2016 at 3:00 AM
To: "3dem at ncmir.ucsd.edu<mailto:3dem at ncmir.ucsd.edu>" <3dem at ncmir.ucsd.edu<mailto:3dem at ncmir.ucsd.edu>>
Subject: [3dem] contamination in cryo samples

Dear all

We are having a serious contamination problem in our cryo preparations and would be grateful for any suggestion. Although this issue has been discussed in the past in this forum, the solutions raised do not seem to work. The attached image shows the contamination on a bad day. I am referring mainly to the lighter, smaller particles (10-20 nm) which are the most persistent. They seem to be above or below the ice layer and are the first to evaporate under the electron beam. The concentration of contaminants is variable.

We are using a Leica EM GP plunger for freezing, and Tecnai T12 and F20 microscopes with Gatan side entry holders. We have tried to replace the ethane cylinder and are in the process of ordering a third one, cleaning the glow discharger machines, different cryo holders, different cryo-transferring units and grids of varying sources. There seems to be no leaks in the compustages of the microscopes.

Thank you for your help

Nadav

--
Nadav Elad, Ph.D.
Electron Microscopy Unit
Weizmann Institute of Science
Rehovot, Israel
Tel: +972 (0) 8 934 2115
Mobile:  +972 (0) 52 3909 420
Email:  nadav.elad at weizmann.ac.il<mailto:nadav.elad at weizmann.ac.il>

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