[Chimera-users] pivot point

[Elaine Meng]

On Apr 30, 2009, at 10:51 AM, Tatyana Fedotova wrote:

> Dear Mrs. Meng,
> I have a question about pivot point.
> Could you explain howfor example  I can rotate part of a helix  from a
> chosen pivot point.
> I fount how I can selet and move atoms. But that's not what I need.
> Thanks,
> Tanya

Dear Tanya,
I can think of two ways to move only part of a structure rather than a  
whole model:

(a) by rotating bonds, see Adjust Torsions, where the bonds define the  
pivots
<http://www.cgl.ucsf.edu/chimera/docs/ContributedSoftware/structuremeas/structuremeas.html#adjust 
 >

(b) with Movement Mouse Mode, which is probably what you were talking  
about
<http://www.cgl.ucsf.edu/chimera/docs/ContributedSoftware/movemode/movemode.html 
 >

Although method (b) does not include control over the center of  
rotation (pivot point), you can set the center of rotation before  
using that tool.  You can set the center of rotation to an atom or  
centroid of a set of atoms by selecting the atom(s) and using  
"Actions... Set Pivot" in the menu.   Or, you can use the "cofr"  
command to do the same thing, or if you have a fairly recent version  
of Chimera (1.4, so a daily build), specify particular X,Y,Z  
coordinates as the center.
<http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/cofr.html>

The center of rotation set as described above also applies when you  
are rotating whole models.  In newer versions of Chimera (1.4), the  
rotation commands "roll" and "turn" also allow specifying the center  
to use when executing that command.
<http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/roll.html>
<http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/turn.html>

Please send Chimera questions to chimera-users at cgl.ucsf.edu rather  
than my personal address, unless you are describing private data.   
Even though I answer a lot of those messages, I might be sick, or on  
vacation, or not know the answer!

Best,
Elaine
-----
Elaine C. Meng, Ph.D.                          meng at 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