On Apr 18, 2009, at 9:43 AM, Antonios Kolocouris wrote:
Hi Elaine, I have obtained the results of the docking claculations of some compounds with a symmetric - by 180 degrees - receptor. To obtain a consistent set of structures for further 3D QSAR I need to know how I can reflect a docking pose by 180 degrees vertically and horizontally with Chimera. My kind regards, Antonios ---------------------------------------------------------------------- --------------------- Antonios Kolocouris, Assistant Professor of Medicinal Chemsitry Department of Pharmacy, Univ. of Athens, Greece
Hi Antonios, The main issue is figuring out the proper transformation to superimpose one binding site on the other. It will not exactly be a reflection (you will still have the same enantiomers) but a rotation. You would need a recent daily build for what I describe. If you are certain only rotations about the exact horizontal and vertical axis are needed, and you know what the center of rotation should be, use the "turn" command with specified axis and center of rotation to move the ligand model(s). The horizontal axis is x, the vertical axis is y. <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/turn.html> The rest of this message addresses the more general case where the axis of symmetry and thus the proper transformation is not known: -- To find out the transformation, (A) put the two parts containing the two binding sites in different models. This could be done by manually text-editing your PDB file to create two files that can then be read into Chimera. Or, if they are already two different chains, you can use the "split" command to divide the already open model into separate models. <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/split.html> (B) superimpose the two binding sites. It could be done with matchmaker, or match, or manually. Which is best depends on the situation. These methods are discussed and there are links to their manual pages here: <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/superposition.html> (C) find out the relative transformation of the two models using the "measure" command, for example to report the transformation of model #0.2 relative to #0.1: measure rotation #0.1 #0.2 the transformation is sent to the Reply Log (under Favorites menu), both as a matrix and as an axis of rotation and point on the axis, as described in the manual page: <http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/measure.html> -- To apply the transformation to the ligands, I would first use the command "reset" (without arguments) to put everything back into their untransformed positions and then either (A) use the "turn" command with specified axis and center of rotation to move the ligand model(s) - or - (B) save the matrix from the Reply Log to a file and then apply it with the "matrixset" command I'm not sure if the "reset" is necessary (some of these transformation issues confuse me), but that's what I would try first. I recommend sending questions to chimera-users@cgl.ucsf.edu rather than to me directly, to be certain they will not fall through the cracks. I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. meng@cgl.ucsf.edu UCSF Computer Graphics Lab (Chimera team) and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html