[3dem] Unrecognised CryoEM contaminant 2

[DANIEL.LUQUE.BUZO.40704]

  Hello,

Thank you for all the suggestions that I have received. After try several
of the suggested solutions, the problem have been finally solved by
ultracentrifugating the samples in Caesium chloride. With this approach, it
is possible to obtain an homogeneous population of particles without the
unrecognised impurities. Thus, the problem (as some of you suggested) came
from the sample and not from the vitrification process. I hope that this
information can be useful of someone find a similar problem.

Thank you all for your kind answers and help

Daniel

Daniel Luque <dluque at cnb.csic.es> escribió:

> Hello
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>    Before a couple of days waiting for the list moderator approval to
> attach the images in the list , I do not have received any response
> (either positive or negative) and I do not have find a mail/way for
> contact. Thus, I have made the images available at our server at:
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>    http://halley.cnb.csic.es/~virus/3DEM/Example_images.pdf
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>    Bellow is text of the original question:
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>    We are doing CryoEM of viral particles. When we check the sample by
> negative staining, a field of intact homogeneous particles without
> significant contaminants is observed. However, when we visualize the
> same sample by CryoEM, additionally to a lower-than expected number of
> particles, we observe an unexpected contaminant mostly located in the
> holes (see attached document with some example images). Does anybody see
> this class of contaminants? Any idea about its origin?
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>    Thanks in advance!
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>    Daniel Luque
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