Hi Martin, Fit an atomic model of the asymmetric unit then use volume zone (Volume Viewer menu entry Feature / Zone) then save the map (Volume Viewer / File / Same Map As…). See the maskZone option description in the volume save command for details https://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/volume.html#output <https://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/volume.html#output> Tom

On Jul 31, 2018, at 7:00 AM, Martin Moncrieffe <mcm35@cam.ac.uk> wrote:

Hi Tom,

A quick question. I have a helical reconstruction (EM) and would like to extract the density for the asymmetric unit from the map. How does one do this?

Best.

__martin