[3dem] Electron dense contamination on cryo grids

[Ben Engel]

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.

Best,
Ben

On Sat, Sep 30, 2017 at 12:20 AM, Stefan Bohn <bohn.stefan.acc at gmail.com>
wrote:

> Hello Sabrina,
>
> 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).
>
> 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.
>
> Hope that helps,
> Stefan.
>
> On Fri, Sep 29, 2017 at 1:52 PM, Sabrina Pospich <
> Sabrina.Pospich at mpi-dortmund.mpg.de> wrote:
>
>> Dear EM community,
>>
>> 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).
>> 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.
>> Has anyone seen those black dots before? We appreciate any hint.
>>
>> Cheers,
>> Sabrina Pospich
>> (Representative for the Raunser lab, MPI Dortmund)
>>
>>
>> _______________________________________________
>> 3dem mailing list
>> 3dem at ncmir.ucsd.edu
>> https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem
>>
>>
>
>
> --
>
> Stefan Bohn
> Gladstone Institute
> 1650 Owens Street
> San Francisco, CA. 94158
> Phone: +1 (415) 476 - 2980 <(415)%20476-2980>
> Fax: +1 (415) 514 - 9736 <(415)%20514-9736>
> stefan.bohn at gladstone.ucsf.edu
>
> _______________________________________________
> 3dem mailing list
> 3dem at ncmir.ucsd.edu
> https://mail.ncmir.ucsd.edu/mailman/listinfo/3dem
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.ncmir.ucsd.edu/pipermail/3dem/attachments/20170930/9f4f4f3b/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Screen Shot 2017-09-29 at 16.52.26.png
Type: image/png
Size: 1729438 bytes
Desc: not available
URL: <http://mail.ncmir.ucsd.edu/pipermail/3dem/attachments/20170930/9f4f4f3b/attachment-0001.png>