Multiple overlapped thon rings

mrc120_rings Hi, I am knew to CryoEM and trying to reconstruct images for alpha-synuclein fibrils from EMPIAR-10195 . Micrographs have been already drift-corrected and dose-weighted using MotionCor2.

After I imported the exposures to CryoSparc, I ran CTF estimation and now am at the exposure curation job. When looking at the thon rings image, there are many other thon rings overlapped on the main one (look at picture). Should I be concerned? What does it mean?

Thank you.

Hi Ginaglezi,
If you are referring to the left side of the image, I think that is just Moire aliasing. It is just an artifact from the monitor.
The Thon rings from your data are displayed on the right half and they look OK to me.


Just a small correction, it’s not from the monitor, but rather from the small size of the rendered image. (The oscillations in the CTF become faster than the Nyquist frequency of the small rendered image).

Thank you both for your responses!

Sorry, I am a new learner too. Here are some images from my data set. How to understand the difference between the left and right side of the image

? Thank you very much!

Hi Yaohui,
The left is a visualization of the CTF model that was fit to the Fourier transform of your image, which is shown on the right side. Generally you would want to see that the CTF model has similar appearance to your Thon rings visible in the Fourier transform, though the Thon rings wont be as apparent in the FT image as will the rings on the left side. I would guess that this particular image has pretty strong astigmatism, or more likely, there is thick/missing ice and the CTF estimation did not produce a model with high confidence.

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Hi Ablakely,
Thank you very much for your explanation!