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

[Mark Ebrahim]

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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