Hi Vijay,

Atom objects have an 'element' attribute which in turn has 'name' and 'number' attributes.  The 'name' attribute is actually the atomic symbol, e.g. H for hydrogen.

You can use normal Python operations, such as 'not', to find these things, so the non-ring ligand atoms are: [a for a in ligand_atoms if not a.rings()]

--Eric

On Jan 17, 2023, at 6:26 PM, Dr. Vijay Masand via ChimeraX-users <chimerax-users@cgl.ucsf.edu> wrote:

Thank you for the details and nice solution, Eric. 

How can I extend the above code to select ring nitrogen and oxygen atoms and to sum charges on different atoms (ring/non-ring)?

Thanks in advance.

 

With Warm Regards

Dr. Vijay H. Masand

Department of Chemistry,
Vidya Bharati College, Amravati, 444 602
Maharashtra, India.
Phone number- +91-9403312628
https://sites.google.com/site/vijaymasand/

On Wed, Jan 18, 2023 at 1:36 AM Eric Pettersen <pett@cgl.ucsf.edu> wrote:

Hi Vijay,

I don't know exactly how efficient you need things to be, but here is some info...

Get all atoms:

from chimerax.atomic import all_atoms

atoms = all_atoms(session)

Filter down to just ligand atoms:

ligand_atoms = atoms.filter(atoms.structure_categories == "ligand")

Ligand ring atoms:

ring_atoms = [a for a in ligand_atoms if a.rings()]

Assign charges to ligand residues:

from chimerax.add_charge import add_charges

add_charges(session, ligand_atoms.unique_residues)

Sum the charges:

charge_sum = sum([a.charge for a in ligand_atoms])

This all assumes the structure has hydrogens.  In particular, the charge sum will be massively negative if hydrogens are missing!  Some of the calls above are covered in the ChimeraX programmer's guide (https://www.rbvi.ucsf.edu/chimerax/docs/devel/index.html, also included in the app under Help), particularly the "API Reference" link.

When you said "select ring atoms" I don't know if you meant just find them (which the above does) or actually select them in the graphics window.  This would do that:

session.selection.clear()

for a in ring_atoms:

a.selected = True

--Eric

Eric Pettersen

UCSF Computer Graphics Lab

On Jan 16, 2023, at 11:03 PM, Dr. Vijay Masand via ChimeraX-users <chimerax-users@cgl.ucsf.edu> wrote:

Dear all

I am looking for an efficient method to select ring atoms of ligands using python in chimeraX. Also, is there any python code/method to get the sum of charges on ligand atoms only?

Thanks in advance.

From

Vijay

With Warm Regards

Dr. Vijay H. Masand

Department of Chemistry,
Vidya Bharati College, Amravati, 444 602
Maharashtra, India.
Phone number- +91-9403312628
https://sites.google.com/site/vijaymasand/

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