Hi JD, Take a look at the new Axes tool (under Tools... Structure Analysis in recent builds of Chimera): http://www.cgl.ucsf.edu/chimera/docs/ContributedSoftware/ structuremeas/structuremeas.html#axes It can show protein helix axes, but you can also calculate an axis for any set of selected atoms. Then you can perform other measurements such as distance to axis, crossing angle between two axes, etc. However, I am not sure whether this computed axis is what you need - it is not exactly an axis of inertia (doesn't depend on the atomic weights of the atoms, for example). Best, Elaine ----- Elaine C. Meng, Ph.D. meng@cgl.ucsf.edu UCSF Computer Graphics Lab and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html On Mar 19, 2008, at 8:40 AM, Jean-Didier Maréchal wrote:
Hi everyone, I was wondering if there is a method available to calculate the principal axis of inertia of a protein (or a part of a protein) in chimera?
If not what would be the easiest way to move forward? All the best, JD