[3dem] Spots in micrographs

[Eric Hanssen]

Hi Saumya,

We have had that discussion a while back, we also discussed this at the Keystone cryoEM a couple of years ago. It seems you are not the only one having that issue. We definitely encountered it a fair few times. However my gut feeling at the time was that the culprit was  our glow discharge system. But I only had exclusion proofs (not the tweezers, not other proteins, not rust on the grids ....).

Since then we purchased a new glow discharge system. I have not seen these spots since. Saying that I am a little less on the microscope than 2 years ago but if some of my staffs or users are reading this please feel free to contradict  me.

Maybe give it a good clean and try again.
Cheers
Eric
(PS I am quite sure I will see them again now I have said that ...)

-----------------
Assoc. Prof Eric Hanssen

Head - Advanced Microscopy Facility
Honorary Principal Fellow - Department of Biochemistry and Molecular Biology

President Australian Microscopy and Microanalysis Society
[acmm2020]
Bio21 Molecular Science and Biotechnology Institute
30 Flemington Road - The University of Melbourne - Victoria 3010 - Australia
email: ehanssen at unimelb.edu.au<mailto:ehanssen at unimelb.edu.au> | Office: +61 3 83442449 | Microscope: +61 3 83442509
Web: www.microscopy.unimelb.edu.au<http://www.microscopy.unimelb.edu.au/>

[bio21]   [amms-logo]

From: 3dem [mailto:3dem-bounces at ncmir.ucsd.edu] On Behalf Of Bajaj Saumya (Dr)
Sent: Friday, 20 March 2020 8:50 PM
To: 3dem at ncmir.ucsd.edu
Subject: [3dem] Spots in micrographs

Dear all,

We are trying to solve the structure of a membrane protein. We have recently started seeing black spots (~1nm) on our micrographs (image attached). The pattern is not uniform, as there are areas where there are no spots. We tried changing buffer and detergent stock - that did not help. The grids are commercial graphene oxide girds and our buffer contains 0.03% GDN detergent.

Have any of you noticed something similar, or can help throw some light on what it could be?

Thanks a lot.
Best regards,
Saumya
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