Weird FSC curve dip and cut-off

Dear colleagues,

I used version 3.2.0 to do the homo-refine and NUR. However, the output FSC curves are all weird with a small dip and are cut off near the reported resolution. I tried to play with a larger box size, but no help. I haven’t met with this kind of problem in other projects. Do you have any suggestions?

Thanks for any of your suggestion!

P31_J69_fsc_iteration_004_after_fsc_mask_auto_tightening

what is your pixel size? It appears you are using binned or downsampled particles

Yes, the pixel size is 1.72A, binned by 2 after extraction from micrograph. The original is 0.43A/pixel (data collected by K3 in super-resolution mode), and was binned by 2 (=0.86, using F-crop factor 1/2) when doing motion correction. Since the particle is elongated, I have to use a large box size, so I downsampled particles.
I just realized that, it’s close to the Nyquist limit, so I need to use the 0.86A/pixel particles, right?

Yes, you are hitting Nyquist, you will want to use the original particles

Thanks for your timely help!