On Mar 9, 2010, at 2:17 PM, Francesco Pietra wrote:

Hello Eric:
I have seen your later correction mail.

I had a bad day, that is little time for chimera and with little
success. Please try to guess were I was faulty.

francesco@tya64:~$ chimera --version
chimera alpha version 1.5 (build 30193) 2010-03-06 09:27:34 GMT
francesco@tya64:~$
This is amd64, at the moment I have no 32bit computer.

<select ligand> selects too much.

<select :residue.number>
<select :residue.name>
do select exactly what I want (which is a small ligand of HEME ligand
of the protein.

The problem was with <define> command

MD-movie...Per-Frame "define centroid :residue.number" ... Apply

then activating the movie gave the same view as not going through the
Per_Frame, i.e., the small ligand does not leave any sphere on the
path. I did not investigate if the sphere are too small to be seen at
the magnification I used, ore have the same color as the background
(black). Very likely, I did some other major mistake.

Not sure what to say.  Works for me.  I've appended an image of centroids tracing the motion of a small ligand in an RNA binding site.  I used a step size of 10 and this 'define' command:

define centroid raiseTool false radius 1.0 color goldenrod sel

"raiseTool false" prevents 'define' from trying to bring up the Axes/Planes/Centroids tool (and update that tool's table) for every centroid created.  The other options control the size and color of the centroid.  I had the small ligand selected so 'sel' is my atom spec.  I tried it a second time with ":35" (which also selects the small ligand) and that worked too.

FYI, "~define" will get rid of all the centroids.

I hope this helps somehow.  Are you sure you had the "Interpret script as" part of the per-frame dialog set to "Chimera commands"?  I can't imagine that you didn't, since you would have gotten some kind of error if it had been interpreted as Python.

--Eric


                        Eric Pettersen

                        UCSF Computer Graphics Lab

                        http://www.cgl.ucsf.edu