[3dem] contamination in cryo samples

[Garry P Morgan]

Nadav-
i’ve been seeing the exact same contamination on my cryo grids, and i’ve come to the conclusion that it’s my quantifoil grids.  i had one plunge freeze session in which i used c-flats, lacey’s and quantifoils…the c-flats and lacey grids had none of this surface contamination, while the the quantifoils were terrible; and every time i’ve used quantifoils i have consistently gotten this contamination.  if nothing else works, i suggest trying a different type of grid, or possibly cleaning your grids (which didn’t work for me)….it’s pretty cheap to test out.
good luck!
Garry

On Sep 1, 2016, at 3:00 AM, Nadav Elad <nadav.elad at weizmann.ac.il<mailto:nadav.elad at weizmann.ac.il>> wrote:

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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