[3dem] your opinion on these images from graphene grids

[Castillon, Reika]

This looks like leopard ice to me (attached, 2D projection and tomogram (suraface and inside view) around ~ 0.5 nm pixel site).
This type of artifact could grow overtime on the surface of cryo-lamella prepared by FIB milling when the dual-beam stage temperature is compromised.
If you take tilt the stage or take a tilt series, you might see the ice grows on the surface of the samples (not inside). The shape and heterogeneity vary also could change overtime.


[cid:33EA86DD-11AE-4981-BE76-FDCB9BCE42A1 at home][cid:FA15A784-E234-4472-B95F-C6759C1BF7CD at home][cid:54B3486F-527C-40CB-A340-9A6160728A96 at home]


REIKA WATANABE CASTILLON Ph.D.
Elizabeth Villa laboratory
Department of Molecular Biology
University of California San Diego 9500 Gilman Dr.
Tata hall room 5100
La Jolla, CA 92093
M/C 0335
Office and Laboratory: 858-822-4038
E-mail: recastillon at ucsd.edu<mailto:recastillon at ucsd.edu>

On Nov 20, 2019, at 6:15 AM, Reinhard Rachel <Reinhard.Rachel at biologie.uni-regensburg.de<mailto:Reinhard.Rachel at biologie.uni-regensburg.de>> wrote:

20.11.2019 at 14:54:
Jacopo,

Assuming these are pictures of a frozen specimen, I would assume the spots
are artifacts of likely radiation damage, especially if they bear no
resemblance to your protein prepared by negative staining.  The spots also
vary in size.  Does that resemble your protein?  If so, then you have a very
heterogeneous sample.

I can understand the comments by David (Belnap)  ...
and take the opportunity to make (more) people aware of Theresa's and Arne's pictures and remarks on sample homo-/heterogeneity and background,  in JSB 203 (Sept 2018) 242-246
Theresa Gewering, D. Januliene, et al .... "Know your detergent ...."
I was for long not aware of this Techn.Note, but only had similar experiences ...
kind regards - Reinhard

--
Prof. Dr. Reinhard Rachel
University of Regensburg
Centre for EM / Anatomy
Faculty of Biology & Preclin. Med.
Universitaetsstrasse 31
D-93053 Regensburg - Germany
tel +49 941 943 -2837, -1720
mail reinhard.rachel at biologie.uni-regensburg.de<mailto:reinhard.rachel at biologie.uni-regensburg.de>
office: VKL 3.1.29
member of the IFSM board

Next microscopy conferences:
- EMC2020 in Kopenhagen, 23.-28.8. 2020 (European conference)
- MC2021 in Vienna (D-A-CH conference)
- IMC20 in Busan, South Korea: Sept 25-30, 2022
- next Microbiol. conferences:  VAAM 8.-11.03. 2020 Leipzig


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