Jason, * tree <javer...@utmb.edu> [2005-05-12 11:39] wrote: > PyMolers, > > The docs leave me stranded here. The wiki page > (http://www.pymolwiki.org/index.php/Rms_Cur) is the same as the docs. > > I'm trying to rms_cur two selections. I keep getting an > ExecutiveRMS-Error: No atoms selected. > error. > > I load two proteins, 1gh2 and 1kao. I then, created two easy selections > A and D as: > > PyMOL>sel A, 1gh2 and n. CA and i. 65-99 > Selector: selection "A" defined with 35 atoms. > > PyMOL>sel D, 1kao and n. CA and i. 64-98 > Selector: selection "D" defined with 35 atoms. > > So far, so good.
Actually not quite so good as you think... > PyMOL>rms_cur A, D > ExecutiveRMS-Error: No atoms selected. > > Can anyone shed some light on this, please? Yes, the problem is the lack of identity within your selections. If you do "help rms_cur" it prints: DESCRIPTION "rms_cur" computes the RMS difference between two atom selections without performing any fitting. USAGE rms_cur (selection), (selection) SEE ALSO fit, rms, intra_fit, intra_rms, intra_rms_cur, pair_fit Unfortunately it leaves out the bit included in: PyMOL>help fit DESCRIPTION "fit" superimposes the model in the first selection on to the model in the second selection. Only matching atoms in both selections will be used for the fit. This is still not quite as clear as it could be. "Matching atoms" are those that are identical in chain, residue name, residue number, atom name, segid and alternate position identifier (if present). So although you had a two lists of 35 C-alphas, none of them matched in all of those aspects. At the end of March, I had announced on this mailing list a script that takes care of this problem when trying to use the "fit" command and it was easy to modify it to use the "rms_cur" command. You can download them from my pymol script site: http://adelie.biochem.queensu.ca/~rlc/work/pymol the scripts are called fitting.py and rms_current.py (I couldn't think of a better name quickly). The usage is: rms_current object1, selection1, object2, selection2 For your case: rms_current 1gh2, n. ca & i. 65-99, 1kao, n. ca & i. 64-98 Note that the object names must not appear in the selections because the atom specifications from object1 are (temporarily) changed to match object2 and selection2. I know this is sort of ugly, but it was to avoid using the slow "alter" command on both selections. I hope this helps. Cheers, Rob -- Robert L. Campbell, Ph.D. <r...@post.queensu.ca> Senior Research Associate phone: 613-533-6821 Dept. of Biochemistry, Queen's University, fax: 613-533-2497 Kingston, ON K7L 3N6 Canada http://adelie.biochem.queensu.ca/~rlc PGP Fingerprint: 9B49 3D3F A489 05DC B35C 8E33 F238 A8F5 F635 C0E2