[3dem] Thinner ice after several microscope uses

[Henning Stahlberg]

Hi,

We had a similar phenomenon: Ice contamination on cryo-EM grids was  
sometimes but not always quite bad, but the second inserted grid was  
often less contaminated than the first one. This was on a JEOL  
JEM-2100F.
I believe the problem might have been related to some weird air-pocked  
formation in the goniometer, potentially between two consecutive O- 
ring sealings. When we left the goniometer without sample holder over  
night, air might have slowly accumulated somewhere and was inserted  
into the column during the first sample transfer. We tried leaving a  
holder in the goniometer over night, but that did not significantly  
improve the situation, as if the "leak" only occurred during sample  
insertion.

An immediate solution could be to insert the warm sample holder in the  
morning, then cool it down in the column, then remove it, mount the  
cryo-grid, and transfer the cold holder back into the column.

JEOL now exchanged the anticontaminator on our JEM-2100F, and on that  
occasion also replaced the goniometer. During that procedure, a lost  
TEM grid was found on the O-ring between the goniometer shell and the  
column housing, which might have caused that problem.

Since this procedure about a month ago, our single-particle cryo-EM  
grids (thin ice on holey film) have not shown signs of contamination.

Henning.



On Nov 24, 2008, at 6:29 PM, Eduardo Sanz Garcia wrote:

> I was analyzing the success rates of my cryoEM sessions and I  
> noticed a trend: When I am the first microscope user of the day I  
> always have thick ice and the chances to obtain better ice improve  
> after several consecutive trials.
> [...]
>


Henning Stahlberg,
Molecular & Cellular Biology, Briggs Hall 5,
University of California at Davis, 1 Shields Ave., Davis, CA 95616, USA
Tel: +1-530-752 8282 (office), +1-530-754 8285 (lab), Fax: +1-530-752  
3085
mailto:HStahlberg at ucdavis.edu
http://stahlberglab.org
http://2dx.org
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