Magnification Anisotropy

Cryo-EM Data Processing
1

Hi everyone,

I am re-processing an old dataset from 2015. It has significant magnification anisotropy. Years ago, I would have modified the raw data after estimating the anisotropy using something like mag_distortion_estimate from the Grigorieff lab. However, now that higher order CTF estimation is built into 3D refinement, and can theoretically correct for mag distortion, is this necessary?

  1. Should I (and can I) correct for mag distortion on the entire micrograph in cryoSPARC?
  2. Is it advisable to correct the frames outside of cryoSPARC and then start the processing from there?
  3. Or should I just process as normal and then let it get handled by higher order CTF estimation during refinement?

I know the real answer is try multiple ways, but the raw data is gain-corrected movies, so the 6k dataset is over 10 TB and is a beast to handle on the machines.

Thanks!

Rick

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I think prob #3, unless the anisomag is so severe as to prevent getting to high enough res for estimation. But discussion here may be useful: Correction of apparent astigmatism due to anisotropic magnification

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Thanks! Slowly downloading 10 TB of data…..so I’ll see how it goes.

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