[Chimera-users] Chimera user, about 'turn' command

Dear Mr./Ms. I'm a Chimera user in FSU. I would like to use Chimera to build some models. I used 'turn' command to rotate the model around the z axis. The command and option was: turn z 27.6923. The model is from a PDB file. But the result was that it should have be, not what I wanted. The atoms should be always in the circle centered in the Z axis, respectively. So my question is: When Chimera open a PDB file recording a protein structure, whether the coordinate axis is exactly the same as that in the PDB file? Thank you for your information in advance. Best, Daniel