Weird behavior: Flipping of reconstruction during refinement

3D Refinement
1

Hi @all,
I made a weird observation lately on an oligomeric structure that kinda resembles a barrel made by stacked donuts.
Obviously, one of the substates is rotated by 180 deg relative to the others. I rotated this manually in chimera, resampled and imported back to cryosparc for homogeneous refinement. I triple checked that the imported volume is in the correct orientation but, funnily, cryosparc always reconstructs upside down.
Any ideas?

Best,
Tarek

2

@tarek For a better understanding of the problem, please can you roughly sketch an oligomer in a way that defines the axis of the 180 degree rotation w.r.t. to a the ring plane, and the rotational states of the remaining donuts. A juxtaposition of the simplified correct and incorrect (“upside-down”) views might also be helpful.