[3dem] How to determine a symmetry of a ring particle?

[Alexander Aleshin]

Could anybody advice me about a way/software to analyze a symmetry of a ring particle imaged by negative staining TEM. The actual symmetry (number of subunits in a ring) is not known, but appears to be within a range of 14-20 subunits per a particle. The number of subunits may also vary  from a particle to  particle. I've got about a thousand projections  with a symmetry axis being perpendicular to the image, but the staining appears to deform particle shapes. As a result, the symmetry of class averages is not obvious.

I am an EM novice, just learned EMAN2 workflow, but I have some experience in structure analysis by Xray crystallography.

Regards,
Alexander Aleshin
Sanford-Burnham Medical Research Institute
Infectious & Inflammatory Disease Center
10901 North Torrey Pines Road
La Jolla, California 92037