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Fwd: Re: coloring surfaces by electrostatic potential from different atoms
by Boaz Shaanan 16 Mar '25

16 Mar '25

Boaz Shaanan, Ph.D. Dept. of Life Sciences Ben Gurion University Beer Sheva, Israel ---------- Forwarded message ---------- From: Boaz Shaanan <bshaanan(a)bgu.ac.il> Date: Mar 16, 2025 18:32 Subject: Re: coloring surfaces by electrostatic potential from different atoms To: ChimeraX Users Help <chimerax-users(a)cgl.ucsf.edu> Cc: Hi Elaine, Thank you so much for the prompt an informative reply. The points about the offset and dielectric are very relevant. In fact, in a quick test that I ran before posing the question I noticed that the coloring of the electrostatic potential on the cofactor was quie dim, probably because of those parameters. I'll also look into the MOLE and pseudo atom coloring. Thanks again. Boaz Boaz Shaanan, Ph.D. Dept. of Life Sciences Ben Gurion University Beer Sheva, Israel On Mar 16, 2025 17:50, Elaine Meng <meng(a)cgl.ucsf.edu> wrote: Hi Boaz, I changed the subject line to try to describe this topic. We aren't the APBS experts but my understanding is that yes, it will generate potential at all points in the rectangular grid, based on the input atoms charges and locations. There will of course be potential values even at grid points where there are no atoms, since electrostatics are fairly long-range interactions. However, the magnitude will depend on what dielectric parameters you have given the calculation. Whether it makes sense: that is somewhat up to your scientific judgement. In my opinion, yes, it makes sense, but you have to think carefully about the "offset" you use to color the cofactor surface. Normally when the surface is on the same atoms that produced the charge, you use a positive offset (default 1.4) to color by values projected that distance outward from the surface, to represent what other outside atoms might "see". If you are coloring a surface of the cofactor atoms to try to understand the potential from the protein that the cofactor "sees," you should consider instead using a negative (say -1.4) or zero offset. The offset is adjustable in the Surface Color dialog options and the "color electrostatic" command: <https://protect.checkpoint.com/v2/r02/___https://rbvi.ucsf.edu/chimerax/doc…> <https://protect.checkpoint.com/v2/r02/___https://rbvi.ucsf.edu/chimerax/doc…> Note that an analogous procedure could be done in ChimeraX with the Coulombic electrostatic potential. For example, see the MOLE channels tutorial where we calculate the Coulombic potential from the protein but then show a surface on pseudoatoms representing a channel calculated by MOLEonline, and then color that channel surface by the protein potential. <https://protect.checkpoint.com/v2/r02/___https://www.rbvi.ucsf.edu/chimerax…> I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. UCSF Chimera(X) team Resource for Biocomputing, Visualization, and Informatics Department of Pharmaceutical Chemistry University of California, San Francisco > On Mar 15, 2025, at 10:30 AM, Boaz Shaanan via ChimeraX-users <chimerax-users(a)cgl.ucsf.edu> wrote: > > Hi friends, > On a related issue: > I'd like to explore the effect of replacing Val by Asp on the electrostatic potential 'seen' by a cofactor which is completely surrounded by the protein (this is relevant for understanding the change in reaction rate following such replacement). I thought of the following steps: > > • Omit the cofactor from the pdb2pqr and APBS. > • Read into chimerax the complete pdb (i.e. including the cofactor). > • Generate the surfaces (protein and cofactor). > • Render the electrostatic potential on both surfaces (i.e. Cofactor and protein surrounding it) and probe the potential on the cofactor. > • Does it make sense? Does APBS generate potential values in the void where the cofactor resides even though it wasn't present in the input pdb2pqr (i.e. in the void where the cofactor resides). > I'd appreciate your input. > Boaz >

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Re: ChimeraX-users Digest, Vol 99, Issue 28
by Boaz Shaanan 16 Mar '25

16 Mar '25

Hi friends, On a related issue: I'd like to explore the effect of replacing Val by Asp on the electrostatic potential 'seen' by a cofactor which is completely surrounded by the protein (this is relevant for understanding the change in reaction rate following such replacement). I thought of the following steps: 1. Omit the cofactor from the pdb2pqr and APBS. 2. Read into chimerax the complete pdb (i.e. including the cofactor). 3. Generate the surfaces (protein and cofactor). 4. Render the electrostatic potential on both surfaces (i.e. Cofactor and protein surrounding it) and probe the potential on the cofactor. 5. Does it make sense? Does APBS generate potential values in the void where the cofactor resides even though it wasn't present in the input pdb2pqr (i.e. in the void where the cofactor resides). I'd appreciate your input. Boaz Boaz Shaanan, Ph.D. Dept. of Life Sciences Ben-Gurion University of the Negev Beer-Sheva 84105 Israel E-mail: bshaanan(a)bgu.ac.il ________________________________ From: chimerax-users-request(a)cgl.ucsf.edu <chimerax-users-request(a)cgl.ucsf.edu> Sent: Friday, 14 March 2025 21:00 To: chimerax-users(a)cgl.ucsf.edu <chimerax-users(a)cgl.ucsf.edu> Subject: ChimeraX-users Digest, Vol 99, Issue 28 Send ChimeraX-users mailing list submissions to chimerax-users(a)cgl.ucsf.edu To subscribe or unsubscribe via email, send a message with subject or body 'help' to chimerax-users-request(a)cgl.ucsf.edu You can reach the person managing the list at chimerax-users-owner(a)cgl.ucsf.edu When replying, please edit your Subject line so it is more specific than "Re: Contents of ChimeraX-users digest..." Today's Topics: 1. sybyl vs amber atom types in ChimeraX (laurene.jacquot) 2. Re: sybyl vs amber atom types in ChimeraX (David A Case) ---------------------------------------------------------------------- Message: 1 Date: Fri, 14 Mar 2025 09:47:39 +0000 From: "laurene.jacquot" <laurene.jacquot(a)etu.chimieparistech.psl.eu> Subject: [chimerax-users] sybyl vs amber atom types in ChimeraX To: "chimerax-users(a)cgl.ucsf.edu" <chimerax-users(a)cgl.ucsf.edu> Message-ID: <MR1P264MB2612AFE1D7D6BEF80D0B069A92D22(a)MR1P264MB2612.FRA P264.PROD.OUTLOOK.COM> Content-Type: multipart/alternative; boundary="_000_MR1P264MB2612AF E1D7D6BEF80D0B069A92D22MR1P264MB2612FRAP_" Dear ChimeraX community, I hope this message finds you well. I am a master student currently working on a project where I need to generate a mol2 file with amber atom types for a protein. Chimera does not manage to parametrize my protein at all, which is why I switched to ChimeraX. ChimeraX does manage to generate a mol2 file, but it writes sybyl atom types. Despite looking on forums, I have not found a feature like in Chimera to write amber atom types instead. I was wondering if such a feature exists in ChimeraX ? Thanks in advance, Best, Laurène Jacquot PSL University, ChimieParisTech -------------- next part -------------- A message part incompatible with plain text digests has been removed ... Name: not available Type: text/html Size: 3823 bytes Desc: not available ------------------------------ Message: 2 Date: Fri, 14 Mar 2025 09:08:36 -0600 From: David A Case <dacase1(a)gmail.com> Subject: [chimerax-users] Re: sybyl vs amber atom types in ChimeraX To: "laurene.jacquot" <laurene.jacquot(a)etu.chimieparistech.psl.eu>, chimerax-users(a)cgl.ucsf.edu Message-ID: <20250314150836.x2iskz4ufcygpsqt(a)pop-os.localdomain> Content-Type: text/plain; charset=us-ascii; format=flowed On Fri, Mar 14, 2025, laurene.jacquot via ChimeraX-users wrote: > >I am a master student currently working on a project where I need to >generate a mol2 file with amber atom types for a protein. I don't have a ChimeraX answer here, but rather a question: why do you need a protein mol2 file with Amber atom types? Amber workflows would not create a mol2 file for an entire protein; but of course, you may need such a file for some other purpose. If so, we may be able to find some Amber tools that does this (or avoids needing it), if the ChimeraX folks themselves don't have a solution. ....dave case ------------------------------ Subject: Digest Footer _______________________________________________ ChimeraX-users mailing list -- chimerax-users(a)cgl.ucsf.edu To unsubscribe send an email to chimerax-users-leave(a)cgl.ucsf.edu Archives: https://protect.checkpoint.com/v2/r02/___https://mail.cgl.ucsf.edu/mailman/… ------------------------------ End of ChimeraX-users Digest, Vol 99, Issue 28 **********************************************

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Ubuntu 24 ARM Daily Builds
by Zach Pearson 15 Mar '25

15 Mar '25

ARM daily builds for Ubuntu 24.04 are now available. — Zach

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Feature suggestion: cubic interpolation for image display
by Ricardo Righetto 14 Mar '25

14 Mar '25

Dear ChimeraX team, (I have a vague memory of discussing this before, apologies if duplicate!) When displaying volumes as images (e.g. cryo-ET volume slices), I see that by default it uses linear interpolation: https://www.rbvi.ucsf.edu/chimerax/docs/user/commands/volume.html#style Would it be possible to offer higher-order interpolation options such as cubic? I love how customizable it is to make figures in ChimeraX, but this is the one feature that we really miss compared e.g. to 3dmod from IMOD. Thank you! -- Ricardo Diogo Righetto

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Dockprep Inquiry
by Emir MALOVIC 13 Mar '25

13 Mar '25

Hello, I am trying to perform some simple docking between a small molecule and a protein. I get the following warning: (UNL) `bash.exe: warning: could not find /tmp, please create!` I was browsing around and noticed I may need to set up ChimeraX Development Environment. Is this true? Thank you, Emir

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ISOLDE refine.eff and phenix.refine
by Shawn Rumrill 13 Mar '25

13 Mar '25

Dear ChimeraX Community, Not strictly ChimeraX related, but probably interesting to some and I've seen some feedback for ISOLDE here... I am using ISOLDE to rebuild a mid-resolution protein/NA model (still adjusting to using ISOLDE, but really powerful tool). I want to refine using phenix.refine, but I am running into a problem with the refine.eff file. The error from the terminal output is below. I've gathered that this is due to a change in parameter terminology from Phenix 1.20 to 1.21. My question is, is there some way to write the refine.eff file with the required information? I would hate to have to manually edit the .eff output file each time I want to run a new refinement in Phenix. Thanks, Shawn Error: Processing files: ------------------------------------------------------------------------------- Found phil, refine.eff Processing PHIL parameters: ------------------------------------------------------------------------------- Adding PHIL files: ------------------ refine.eff Unrecognized PHIL parameters: ----------------------------- refinement.input.pdb.file_name (file "refine.eff", line 6) refinement.input.xray_data.file_name (file "refine.eff", line 9) refinement.input.xray_data.labels (file "refine.eff", line 10) refinement.input.xray_data.high_resolution (file "refine.eff", line 11) refinement.input.xray_data.low_resolution (file "refine.eff", line 12) refinement.input.xray_data.r_free_flags.file_name (file "refine.eff", line 14) refinement.input.xray_data.r_free_flags.label (file "refine.eff", line 15) refinement.input.xray_data.r_free_flags.test_flag_value (file "refine.eff", line 16) Sorry: Some PHIL parameters are not recognized by phenix.refine. Please run this program with the --show-defaults option to see what parameters are available. PHIL parameters in files should be fully specified (e.g. "output.overwrite" instead of just "overwrite")

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Re: Inquiry to docking protein onto lipid bilayer
by You, Youngki 12 Mar '25

12 Mar '25

Hello Tommy, You can use this server (PPM in OPM site), https://opm.phar.umich.edu/ppm_server3_cgopm , to determine the orientation and depth of your protein in the membranes. After that, you can use the model from PPM in CHARMM-GUI. Best, Youngki ________________________________PNNL__ Youngki You, PhD Post Doctorate RA, Biochemical Mechanisms Structure, Function & Design Biological Sciences Division Pacific Northwest National Laboratory Tel: +1 (509) 371-6660

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Inquiry to docking protein onto lipid bilayer
by Tommy Tong 12 Mar '25

12 Mar '25

Dear ChimeraX experts, Good afternoon. My name is Tommy from San Diego Biomed. I am a beginner to ChimeraX version 1.9. May I ask if it is possible to use ChimeraX to dock a membrane protein into a lipid bilayer? I obtained Phosphotidylcholine bilayer (POPC) structure from CHARMM-GUI webpage https://charmm-gui.org/?doc=archive&lib=lipid_pure, and was wondering if it is possible to “place” a protein into this POPC structure in ChimeraX. Your help and advice on this is greatly appreciated. Thank you. Sincerely, Tommy

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Obtain individual RMSD values
by javisanchezdelrio＠gmail.com 12 Mar '25

12 Mar '25

Hello, I have an issue when applying matchmaker command in ChimeraX. When I execute the command: matchmaker #1 to #2 showAlignment true I obtain the alignment with the bars in the upper layer showing the individual RMSD of each residue. But the results yields the overall RMSD of the alignment (i.e. RMSD between 108 pruned atoms). Is there any way to obtain those individual RMSDs of the alignment as a file or have them printed in the log for post-processing? Thank you in advance

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Dividing a huge model (& map) into smaller chunks
by Alejandro Buschiazzo 12 Mar '25

12 Mar '25

Dear chimeraX developers/users Using version 1.9, I am trying to divide a very big mmcif model (230K + nonH atoms; >130 chains) and corresponding mrc map, into a number of smaller mmcif files (and corresponding cropped maps, covering just those parts). What I’ve tried so far unsuccessfully: I can create dummy atoms with build start atom, at desired x,y,z points, so that I can then use select zone to select a radius and keep parts near each dummy atom. Yet, that is suboptimal: I would largely prefer to keep (build) boxes, and not spheres, ensuring complete recovery and no blind spots. So that each box slightly overlaps with the neighboring one, and systematically covers the whole original map volume. 1. How can I generate a script that will do this "systematic windowing” screening, making boxes of a defined side-length at each step, and keeping the model within? 2. How should I then crop the original map, so that it covers each box (with a small padding on the borders)? 3. How should I stitch back the models, so that I don’t loose any atomic coordinates information? (of course that stitching will be done after I do some refinement work on each boxed model vs map) So sorry for the many questions! I’ve been trying hard to find this kind of strategy, and just can’t seem to succeed…. Thank you very much in advance Alejandro -- Alejandro Buschiazzo, PhD Associate Professor Laboratory of Molecular & Structural Microbiology Institut Pasteur de Montevideo Mataojo 2020 Montevideo 11400 URUGUAY Phone: +598 25220910 ext. 120 Fax: +598 25224185 https://pasteur.uy/en/laboratories/molecular-and-structural-microbiology/

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