[chimerax-users] Proposal to an add on

[Elaine Meng]

Hi Heather,
The problem is that Chimera and ChimeraX do not really have a way to measure the size of a pocket that has any openings.  I'm guessing that other programs have solved this problem, but I do not have a list off the top of my head, nor have I tried them, nor do I know if they work on something on the scale of a viral capsid.  

Maybe others on this list have suggestions of what other program(s) to try?

The only one I've used is CASTp, but that is generally for something like a single protein (enzyme or receptor).  I don't know if you could run it on a large assembly or not.
<http://sts.bioe.uic.edu/castp/index.html?2cpk>
<http://sts.bioe.uic.edu/castp/calculation.html>

My only idea in Chimera/ChimeraX is to create an idealized sphere or icosahedron shape of the largest size that nests within the inner surface of your capsid (determined iteratively by eye), and then calculate the volume of idealized sphere or icosahedron.  The idealized surface could be created with "shape" and measured with "measure volume"
<https://rbvi.ucsf.edu/chimerax/docs/user/commands/shape.html>
<https://rbvi.ucsf.edu/chimerax/docs/user/commands/measure.html#volume>

Another way to draw a sphere shape is with the Volume Eraser tool, e.g. in ChimeraX, click "Right Mouse" in the toolbar tab across the top and then the icon that looks like a surface with a pink sphere on it.  Then you get a Map Eraser dialog that has a slider for radius, which may be easier than using "shape sphere" or "shape icosahedron" repeatedly, and you can drag the sphere around to reposition using the right mouse (= trackpad + Alt on Windows, trackpad + command key on Mac)

Best,
Elaine
-----
Elaine C. Meng, Ph.D.                       
UCSF Chimera(X) team
Department of Pharmaceutical Chemistry
University of California, San Francisco

> On Aug 31, 2022, at 6:28 AM, Noriega, Heather via ChimeraX-users <chimerax-users at cgl.ucsf.edu> wrote:
> 
> Hello,
> 
> I hope everyone is doing well. I know I have asked this before about the molmaps and have been trying to work around the "holes", in order to create a solid map for the inner volume calculation. It works very well with the AAVs, however with the other subfamilies because of their larger pores it makes it to where it is an inconsistent volume contour, and I believe it throws off the inner volume calculations. I propose to add an element to only cover the pores as a means to make the contour thinner to create a more realistic inner volume calculation. I would like to help with this feature, as my skills have improved within the last year since I first started using Chimera and ChimeraX for my project. I am unsure how I go about this and your response.
> 
> I have reached out before and most of the time it ends in maybe trying another software. There is no other software that is remotely comparable to this molmap feature that is as user-friendly as it is in ChimeraX. I would really like to continue the use of ChimeraX. I have also thought of possibly trying to create a way for the molecular surface to work with the volume blob feature, but it still comes down to the pores creating the holes. A mechanism to create a feature of only covering the pores could be useful for not only my project but others that may have similar issues. Please let me know what your thoughts are as I would like to contribute to this resolution, but would also need some direction on how to start it. Thank you and I hope to hear from you soon.
> 
> 
> Thank you,
> 
> Heather Noriega
> PhD-Pharmaceutical Science student 
> Howard University
> heather.noriega at bison.howard.edu
> 520-203-1883
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