From: Axel Kohlmeyer (
Date: Wed Sep 13 2006 - 14:18:03 CDT

On 9/13/06, Zu Thur Yew <> wrote:
> Hi,
> I'm rather new to VMD, I was wondering if anyone has done anything
> similar...

it is rather trivial to implement with a little bit of experience.

> I have 2 crystal structures as 2 frames in a single pdb file and want to
> draw vectors/arrows from each CA atom that give a feel of the
> conformational transition.

> Any advice would be much appreciated!

try the attached scripts.

first you need to source the vec_draw_lib.tcl script file
(or install the corresponding rpm from the vmd biocore)
that has a generic implementation of a point to point arrow.

then you source the cavec.tcl script.
now you can load your file and then do.

set casel [atomselect top {name CA}]
frametoframepos $casel 0 last

and you should see the desired result.

> Thanks!

Axel Kohlmeyer
  Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
If you make something idiot-proof, the universe creates a better idiot.