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<div class="">Dear Alexey, Sameer, Stefan and Ben,</div>
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<div class="">thanks for sharing your ideas with us. We have already suspected the contamination to be gold. However, we hardly use gold fiducial in our lab and even less frequent with the plungers. We will clean our equipment more carefully in the future and
hope that solves the problem. </div>
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<div class="">Cheers,</div>
<div class="">Sabrina</div>
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<blockquote type="cite" class="">
<div class="">On 30 Sep 2017, at 06:46, Ben Engel <<a href="mailto:bdengel@gmail.com" class="">bdengel@gmail.com</a>> wrote:</div>
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<div dir="ltr" class="">I agree with Stefan that they look like Gold fiducials (5nm or 10nm). In addition to tweezers, if you are using a plunger such as a Vitrobot, it is also possible that the contaminating particles are on the pads where you place the rings
of blotting paper.
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<div class="">Best,</div>
<div class="">Ben</div>
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<div class="gmail_quote">On Sat, Sep 30, 2017 at 12:20 AM, Stefan Bohn <span dir="ltr" class="">
<<a href="mailto:bohn.stefan.acc@gmail.com" target="_blank" class="">bohn.stefan.acc@gmail.com</a>></span> wrote:<br class="">
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<div dir="ltr" class="">Hello Sabrina,
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<div class="">these particles look remarkably similar to nanogold particles I used before. These particles also preferred proteins (they loved the 26S) or showed clusters similar to the ones on the lower right image. They come in sizes from 2 to >5nm (can't
see a scale-bar, but it seems your contamination is of similar size). </div>
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<div class="">Is anyone using fiudical markers of any sort in your lab? One source of contamination would be the tweezers that hold the grid during plunging. In case those tweezers are shared among several 'plungers' and not readily cleaned after use of the
markers, they could appear on the next grid being plunged.</div>
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<div class="">Hope that helps,</div>
<div class="">Stefan.</div>
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<div class="h5">On Fri, Sep 29, 2017 at 1:52 PM, Sabrina Pospich <span dir="ltr" class="">
<<a href="mailto:Sabrina.Pospich@mpi-dortmund.mpg.de" target="_blank" class="">Sabrina.Pospich@mpi-dortmund.<wbr class="">mpg.de</a>></span> wrote:<br class="">
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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=""><span id="cid:115172A7-0078-461B-88F7-50ABF840BA2F"><Screen Shot 2017-09-29 at 16.52.26.png></span></div>
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-- <br class="">
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Stefan Bohn<br class="">
Gladstone Institute<br class="">
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