I am using the Symmetric Molecule Copies plug-in with Chimera. I am wondering if there is a preferred way to orient an EM volume so that it is centered around the z-axis at the origin. From my experience with this plug-in, symmetry related molecules are generated around z-axis at the origin of the viewing area. I am finding that my maps tend to be close, but not exactly oriented around the z-axis for a helical volume. Molecules fit into a portion of the map then tend to have slightly askew symmetry mates relative to the volume (presumably because the z-axis of the map is not exactly oriented along the origin of the symmetry z-axis). After playing around with various map tools (MAPMAN, Priism), I am still not satisfied with my orientation protocol and wonder if anyone can suggest a tried and true method for this. Thanks Albion