Strange FSC curve

I am doing the helical refinement, but the FSC curve is always strange,like this:
does anyone know why?and how to solve this? :worried:

Hi @SJH,

Thanks for the post! I have encountered similar FSCs to this when processing helical data – here are some questions/comments:

  • Are you confident in the applied symmetry for the dataset? Incorrect symmetry can often create unhealthy FSCs like these
  • Does the model/density appear as expected, with clear examples of secondary structure? Helical reconstruction has unique pitfalls relative to globular protein reconstruction via cryo-EM, and so manual inspection of the density is (especially) necessary; see Prof. Egelman’s paper on the subject here.
  • Are you using an initial model, or are you allowing the job itself to initialize the density?