[Chimera-users] rotate a helix

Hi there, I would like to rotate a helix at a particular angle. How could I accomplish the following? 1. How to define the central axis of the helix in chimera? 2. How to set a particular angle to rotate? 3. I do this on a helix belonging to a GPCR, with the loops firstly broken for rotation and then perhaps need to rejoin them. How to join them back? 4. After joining, should I just redo energy minimization for the loops concerned? Much thanks!