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<div style="direction: ltr;font-family: Tahoma;color: #000000;font-size: 10pt;">Hi Sabrina,<br>
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I've seen the same dots (top and bottom right). In my case I saw them in areas where the ice was too thin and interpreted it as aggregated proteins. Perhaps you need to change the grid making conditions (reduce blotting time slightly ?)<br>
You could also look at a different part of the the current grid where the ice may be of more optimum thickness.<br>
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Hope this helps.<br>
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Best,<br>
Sameer<br>
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<div style="font-family:Tahoma; font-size:13px">________________</div>
<div style="font-family:Tahoma; font-size:13px">Sameer Singh, PhD
<div>Albert Einstein College of Medicine</div>
<div>1300 Morris Park Avenue</div>
<div>New York, NY - 10461</div>
<div>Phone: 718-430-2048 </div>
<div>Cell: 917-848-9319</div>
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<div id="divRpF958006" style="direction: ltr;"><font size="2" color="#000000" face="Tahoma"><b>From:</b> 3dem [3dem-bounces@ncmir.ucsd.edu] on behalf of Sabrina Pospich [Sabrina.Pospich@mpi-dortmund.mpg.de]<br>
<b>Sent:</b> Friday, September 29, 2017 4:52 PM<br>
<b>To:</b> 3dem@ncmir.ucsd.edu<br>
<b>Subject:</b> [3dem] Electron dense contamination on cryo grids<br>
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<div class="">Dear EM community,</div>
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<div class="">we are currently struggling with an electron dense contamination on our cryo-EM grids (see images below - left panel volta phase plate images with different phase shift - right panel standard TEM images at different magnifications).</div>
<div class="">The dots seem to appear almost randomly and like to stick to protein. We furthermore see them independently of the glow discharger (GloCube or an older device) and plunger (Cp3 or Vitrobot) we use and also for both C-flat and Quantifoils grids.</div>
<div class="">Has anyone seen those black dots before? We appreciate any hint.</div>
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<div class="">Cheers,</div>
<div class="">Sabrina Pospich</div>
<div class="">(Representative for the Raunser lab, MPI Dortmund)</div>
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<div class=""><img id="39D8F63D-ED7D-49C3-8DBB-9C068CF3AADB" src="cid:115172A7-0078-461B-88F7-50ABF840BA2F" class="" width="748" height="386"></div>
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