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<div>Hi Henning,</div>
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<div>There is one more thing you may check, the comma free alignment is important to the high resolution, beam tilted too much would distort images.</div>
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<div>Dan</div>
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<div>Dan Shi</div>
<div>Janelia Research Campus, HHMI</div>
<div>19700 Helix Dr, Ashbirn</div>
<div>VA 20147, USA </div>
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<span style="font-weight:bold">From: </span>3dem <<a href="mailto:3dem-bounces@ncmir.ucsd.edu">3dem-bounces@ncmir.ucsd.edu</a>> on behalf of Henning Stahlberg <<a href="mailto:henning.stahlberg@unibas.ch">henning.stahlberg@unibas.ch</a>><br>
<span style="font-weight:bold">Date: </span>Thursday, May 11, 2017 at 9:08 AM<br>
<span style="font-weight:bold">To: </span>3dem <<a href="mailto:3dem@ncmir.ucsd.edu">3dem@ncmir.ucsd.edu</a>><br>
<span style="font-weight:bold">Subject: </span>[3dem] Request for help to find source of resolution loss in cryo-EM<br>
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Hi,<br class="">
<br class="">
We have a strange problem on one of our instruments (Titan Krios with Quantum-LS GIF and K2 Summit in counting mode).<br class="">
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.<br class="">
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. <br class="">
However, while the 3.7A ring shows that anisotropic resolution loss, the 2.1A ring is still isotropically present. An example image is attached.<br class="">
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Does anybody have an idea what could cause such a behavior?<br class="">
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Thanks,<br class="">
<br class="">
Henning.<br class="">
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<div class="">Henning Stahlberg, PhD<br class="">
Prof. for Structural Biology, C-CINA, Biozentrum, University Basel<br class="">
Mattenstrasse 26 | D-BSSE | WRO-1058 | CH-4058 Basel | Switzerland<br class="">
<a href="http://c-cina.org" class="">http://c-cina.org</a> | Tel. +41-61-387 32 62<br class="">
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