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

[Jacopo Marino]

Dear Community,

I would like to ask you what you think about these images we took by 
using graphene grids (suspended monolayer graphene on TEM grid 
substrate, quantifoil gold, purchased from Sigma). We are puzzled 
because if one area is exposed with the usual 20 electrons for 2 
seconds, it is very difficult to see if there are particles or not. 
However, when the same area is re-exposed with the same dose or for 
longer, there are particles-like entities appearing, which we wonder 
whether they could be an artefact from the longer exposure. 
Interestingly, by exposing for even longer (200 electrons), particles 
seem not be destroyed, which makes us doubting this is protein.

Here is the link with the images, where 001.tif is the image we took 
with normal exposure, 18.tif is exposed twice, while 19.tif is the one 
shot at least three times. We used a Talos at 200 kV, pixel size 1.61.

https://www.dropbox.com/sh/5rb59jwsiu6zcrq/AAAze6dKhR4P4Wzb7LMCs75Ba?dl=0

Thank you for your help !

Jacopo

-- 
Dr. Jacopo Marino
Laboratory of Biomolecular Research
Paul Scherrer Institute
OFLB/005
5232 Villigen PSI, Switzerland
tel: +41 56 310 5484 (or +41 56 310 5777)
e-mail: jacopo.marino at psi.ch