[3dem] Request for help to find source of resolution loss in cryo-EM

[Alex de Marco]

Hi Henning,

Is the behaviour specific of the imaging conditions you describe or can you
see a similar result at other magnifications?

We had some grounding issues that displayed a similar behaviour. It took
some time to get to the root of it.

In our case the resolution cut was independent from the magnification, but
fixed at about 2/3 Nyquist,

Best

Alex





*From:* 3dem [mailto:3dem-bounces at ncmir.ucsd.edu] *On Behalf Of *Mark
Ebrahim
*Sent:* Friday, 12 May 2017 6:05 AM
*To:* Henning Stahlberg <henning.stahlberg at unibas.ch>; 3dem <
3dem at ncmir.ucsd.edu>
*Subject:* Re: [3dem] Request for help to find source of resolution loss in
cryo-EM



Hi Henning,



Greetings from New York.



This is an interesting photo. How reproducible is this behavior?



My first step would be to insert a cross grating and have a look at the
information limit; after seeing that we could start to theorize what the
problem could really be.

​



Best,

Mark


*------------------------------*

*Mark Ebrahim*

Senior Staff Scientist

Cryo Electron Microscopy Resource Center (CEMRC)

The Rockefeller University

1230 York Avenue

New York, NY 10065
------------------------------

*From:* 3dem <3dem-bounces at ncmir.ucsd.edu> on behalf of Henning Stahlberg <
henning.stahlberg at unibas.ch>
*Sent:* Thursday, May 11, 2017 9:08 AM
*To:* 3dem
*Subject:* [3dem] Request for help to find source of resolution loss in
cryo-EM



Hi,

We have a strange problem on one of our instruments (Titan Krios with
Quantum-LS GIF and K2 Summit in counting mode).
When recording images at low mag (1.04 A/px for the 4k images) and low-dose
conditions of a partly devitrified sample, and compute the FFTs, we can see
the 3.7A ice ring and also the second-order 2.1A ice ring, sometimes a
third-order ring in the corners at 1.7A resolution.
We recently observed a resolution loss visible in the FFTs only in the
vertical direction, shown by an amplitude decay in the upper and lower
quarter of the FFTs.
However, while the 3.7A ring shows that anisotropic resolution loss, the
2.1A ring is still isotropically present.  An example image is attached.

Does anybody have an idea what could cause such a behavior?

Thanks,

Henning.


Henning Stahlberg, PhD
Prof. for Structural Biology, C-CINA, Biozentrum, University Basel
Mattenstrasse 26 | D-BSSE | WRO-1058 | CH-4058 Basel | Switzerland
http://c-cina.org
<https://urldefense.proofpoint.com/v2/url?u=http-3A__c-2Dcina.org&d=DwMFAg&c=JeTkUgVztGMmhKYjxsy2rfoWYibK1YmxXez1G3oNStg&r=yFrUlH9O04U9FBwxVIdysCYHghM3ThWbjLvKfnev9gQ&m=O8br31vcM9PsZG9JLWoGbKKE3Fn8LksrXXsWo0uQeuo&s=gD8H_SbRDYBegOWKgL_wUmFQV274mYNF8p4Ayx3Mxho&e=>
| Tel. +41-61-387 32 62
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