Hi Michael,

Perhaps you can compare the orientation between the exact symmetric placement of a chain and the actual position by measuring the translation and rotation angle needed to align the two. By rotation angle I mean that any rotation can be represented as a rotation about a single axis (which depends on the rotation). I do not understand what you mean by rotation angles about x, y and z axes. As I mentioned that depends on the order of the rotations and therefore is rarely used. In the Chimera match command or matchmaker tool the optimal rotation matrix is computed -- it is *not* decomposed into separate x, y and z rotations during that calculation. I suppose if your system has symmetry about the z axis you could ask what rotation about z best aligns a chain with the exact symmetric chain location. In other words, only a z-axis rotation rather then rotation about an arbitrary axis would be allowed. Chimera does not have code for that and I have never heard that number reported.

If you spell out precisely what angle is needed I can give better advice on how to get it from Chimera.

Tom

From: "Stohr, Michael" stohr@uni-mainz.de To: "Thomas Goddard" goddard@cgl.ucsf.edu Date: Mon, 27 Nov 2006 09:51:31 +0100 Subject: AW: Get angles in degree out of Rotation matrix

Hi Tom,

Thanks a lot for your description. It does not fit completely my demand. I will rephrase my question, is there a simple way to determine the three angles between the two 3d-structures of two identical chains? The background is that my molecule is not absolutely symmetrical and I want to quantify the asymmetry. So, I want to be able to say, this angle between this two chains differs from ideal symmetry angle by X degrees for different directions (x, y, z). I thought the rotation matrix would be the way to do so, but it does not seem so. I've found a not very precise method by using the distance tool and trigonometric functions. Therefore, if there is no answer for my question it will be ok at first especially I have to finish my theses very soon. By the way, in which order does for example the tool match or matchmaker rotates a structure or is this not predictable?

Thanks for your afford, Michael