Symmetry made huge dip in FSC

Troubleshooting
1

image

Dear colleagues,

I am recently working on protein possessing I1 symmetry, but when I applied the symmetry the FSC got this huuuge dip like the attached image. But overall map quality is fine. If I apply no symmetry, then the FSC curve is totally fine. I have no idea what is going on with it. Some of you could give me any suggestions? It would be a great help.

Thanks!
Simon

2

Looks like beam tilt or some other aberration. Have you tried running global CTF refinement using the output of this to analyze?

Given it has icosahedral symmetry I am assuming it is big and shell-like, so refinement of anisotropic mag may also be worth trying.

Cheers
Oli

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3

Your suggestion amazingly improved my data, thanks a lot!

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