Hi Damien, You can measure the relative orientation of the two models with the "measure rotation" command: measure rot #0 #1 which produces output in the reply log (Favorites / Reply Log) like Position of 2gbp.pdb (#1) relative to 1a0m.pdb (#0) coordinates: Matrix rotation and translation 0.90028335 0.21178251 -0.38031310 38.41870000 0.30675800 0.31121759 0.89946825 -28.00030000 0.30885177 -0.92644038 0.21521804 53.80560000 Axis -0.93447169 -0.35270388 0.04860698 Axis point 0.00000000 15.26078714 51.99569332 Rotation angle (degrees) 77.68070000 Shift along axis -23.41004496 Also it draws the rotation axis on the screen (append "show false" to suppress that). The rotation is shown as a matrix and as axis/angle in the output. You can compute the quaternion equivalent of the rotation if you need that: (sin(a/2)*axis, cos(a/2)) where a is the angle. The "measure" command is only in Chimera 1.4 so get a daily build to use it. http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/measure.html#rotation Tom -------- Original Message -------- Subject: [Chimera-users] Orientation and quaternion From: Damien Larivière <damien.lariviere@fourmentinguilbert.org> To: chimera-users@cgl.ucsf.edu Date: 8/6/09 11:11 AM

Dear all,

In the attached image, two copies of the FtsZ protein (pdb 1FSZ) are displayed in Chimera.

I would like to know the orientation of one copy with respect to the other one. Is there a way to get this information ? Is it possible to get a quaternion instead of a set of Euler angles ?

My best regards

Damien

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