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

[Henning Stahlberg]

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 | Tel. +41-61-387 32 62


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