- Chimera-users - RBVI Mailing Lists

Chimera inquiry
by Danny Turin 18 Sep '19

18 Sep '19

Dear Sirs and Madames, I first want to start by sharing my appreciation with you for creating this program. It has been very helpful in my biochemistry course. I have been using the program to compute the total area and volume. Is there a way to only select either the polar or non-polar residue in the surface structure to determine volume and area. Thank you for your time. Sincerely, *--Daniel Turin * University of Minnesota Class of 2021, B.S. Health Sciences l turin005(a)umn.edu l (651)-600-0805 l

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Unable to Find Function
by Bailey Onken 17 Sep '19

17 Sep '19

Hello, I am currently a student in Biochemistry. I have a protein and I am trying to separate polar and nonpolar residues located on the surface of these molecules and then finding the values for the surface area associated with polar and nonpolar areas. If you can help me get to this function I would be very grateful. Thank you very much, Bailey -- *Bailey Onken *| Student, University of Minnesota Rochester 507.329.7409 | onken031(a)umn.edu

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How to draw 3-fold axis of a Icosahedron
by sunyeping 17 Sep '19

17 Sep '19

Dear everyone, I created an icoshedron with "Tool>high-order structre>Icoshedron surface" menu. Do you know how to draw 3-fold axis of a Icosahedron so that I can see the 3-fold symmetry center on the icoshedron surface? Thank you in advacne.

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Command line equivalence for Render by Attribute radii
by Sygusch Jurgen 16 Sep '19

16 Sep '19

Hello, I cannot seem to find the command line equivalence for Render by Attribute radii. I am trying to display a tunnel where the atom B-factors represent the tunnel radius. I am able to display the tunnel as expected by using the GUI. In the GUI, when I do Tools --> Depiction --> Render by Attribute --> atoms --> My Model; then Render Attribute --> bfactor; Radii --> Atom Style --> Sphere, I get the expected result of the tunnel diameter varying according to Bfactor (tunnel radius). What is the command line equivalence for doing this? I cannot seem to find it. Thank you for looking into this.

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Selecting residues with zones when reference is absent
by Carlos G. Oliver 16 Sep '19

16 Sep '19

Hello, I would like to select all ligands that are within a distance of nucleic acids but above a distance from proteins. The selection command I have so far is: `select nucleic acid z<10 & protein z>10 & ligand` This works for PDBs that contain both nucleic acids and protein. However, some will only contain nucleic acids, and in this case the `protein z>10` condition will result in an empty selection even when there is a valid ligand. I was wondering if there was a way to check whether the model contains protein to run a different selection command for each case, or to use a different selection command which handles both cases. Thanks! Carlos G. Oliver

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Dockprep OT2 C terminal question
by Danilo Boškovic 16 Sep '19

16 Sep '19

Dear caretakers, I have a non-standard residue OT2 (C terminus last O atom) that does not get recognized in the amber force field (everything else is fine). How do i rename this residue so it is properly accounted when adding charge? Sincerely, D. Boskovic

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Max 100 residues for local bug?
by Danilo Boškovic 16 Sep '19

16 Sep '19

Dear caretakers, I tried to do autodock vina but as soon as i did i got an error that i can only do max 100 residues. I use a local installation of AVina. Is this a bug or is there somewhere something im missing? 41965 build number 1.13.1 version Sincerely, D. B.

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Where is the radius.nc map file in the Semliki Forest virus?
by sunyeping 16 Sep '19

16 Sep '19

Dear everyone, The Semliki Forest virus tutorial (https://www.cgl.ucsf.edu/chimera/data/tutorials/semliki/semliki.html) mentioned a radius.nc which is used for visualization of the layer. However, the tutorial doesn't describe where the reader can download it. Do you know where to get thid file? Thank you in advance. Yeping Sun

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Re: [Chimera-users] Electrostatic potential molecular surfaces
by Elaine Meng 12 Sep '19

12 Sep '19

Hi Fernando, Our resources don’t allow spending much time on consulting with individual research projects, sorry, and I can only answer mostly as it pertains to Chimera as I don’t know the details of parameters developed by other people or other programs. Also Chimera questions should be sent to this mailing list instead of to me directly so that other people can also benefit, unless private data are discussed or attached. You found an old script that is really special-purpose, finding the surface area that is more red than blue after coloring by electrostatic potential. Note that this would include surface that looks white but has a tiny, tiny tint of pinkishness. Also, the surface area that is more blue than red is just the complement of the surface that is more red than blue. In other words, if the surface is 75% red>blue then it is 25% blue>red because very little if any will be pure white. They always add up to the total surface. So no, you cannot use these scripts to figure out how much of the surface is polar or nonpolar. It may not matter given the above, but which method, set of charges, and what parameter values to use for electrostatic potential (ESP) calculations are research decisions that I cannot make for you. There are always tradeoffs, and different people have different opinions, etc. I don’t know python, but your generalization to coloring by hydrophobicity by identifying cornflower blue vs.goldenrod might be wrong. Red vs. blue is simpler since they are RGB color components. However, even if the color comparison is done correctly, the logical problem is the same, they always add up to the whole surface, and nearly white areas will always be combined with one side or the other. However, you can get the total surface area given some range of hydrophobicity values independent of any coloring. Hydrophobicity in this case is just a constant lookup value for each type of amino acid, according to this table (kdHydrophobicity column): <http://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/midas/hydrophob.html> You would have to decide yourself which range of values is polar or nonpolar, but then you could just select all the residues that are less than or more than a certain value, e.g. command: select :/kdHydrophobicity>0.0 Alternatively you could just use command: select polar select ~polar …but you might not agree with what amino acids are considered polar, as shown in a table in this page: <http://www.rbvi.ucsf.edu/chimera/docs/ContributedSoftware/resprop/resprop.h…> Then if surface is shown you could add up the area for the selected residues, e.g. menu: Tools… Structure Analysis… Attribute Calculator, and in that tool calculate attribute named whatever you want for “molecules” with Formula: sum(areaSAS.residue) (… or SES instead of SAS, to be compared with the corresponding total area given in the Reply Log when you show the surface) with option to “Restrict formula domain to current selection” and “Show calculation results in Reply Log" turned on, other options turned off, click Apply. <http://www.rbvi.ucsf.edu/chimera/docs/ContributedSoftware/calculator/calcul…> Totally separate and not related to Chimera, but I happen to know of this web server you might be interested in, for comparing ESP of related proteins: <https://pipsa.h-its.org/pipsa/> Best regards, Elaine ----- Elaine C. Meng, Ph.D. UCSF Chimera(X) team Department of Pharmaceutical Chemistry University of California, San Francisco > On Sep 11, 2019, at 2:16 PM, Fernando Villa <fer.vdl1928(a)gmail.com> wrote: > > > Dear Elaine C. Meng, Ph.D > > I have some questions about electrostatic potential molecular surfaces and protein comparison. > > 1. The following scripts are added, edited from the redarea.py script of link http://plato.cgl.ucsf.edu/trac/chimera/wiki/Scripts, considering that the script allows reading the surface in Å2 colored more red than blue area. > > 1. Add scripts: > > Command: > > > open > > -blue_area_03.py > > -cornflowerblue_area_03.py > > -goldenrod_area_02.py > > -red_area_02.py > > (the scripts are attached) > > > 2. I used the following commands: > > > open 4MZ2 > > > delete solvent > > > addh > > > addcharge > > > Surface > > coulombic -10 red 0 white 10 blue > > > The electrostatic potential surface is presented by Coulombing coloring Surface: > > > > <image.png> > I execute the commands: > > > redarea #0 > > red area 3562, total area 5730, ratio 0.6217 > > > bluearea #0 > > blue area 2168, total area 5730, ratio 0.3783 > > > The dominant areas of both colors are obtained. > > The following command is input: > > > rangecolor kdHydrophobicity min cornflowerblue 0 white max goldenrod > > > > <image.png> > Next: > > > cornflowerbluearea # 0 > > cornflowerblue area 4109, total area 5730, ratio 0.7171 > > > > goldenrodarea # 0 > > Goldenrod area 1621, total area 5730, ratio 0.2829 > > > So, I believe (I'm not sure): > > Blue area + Red area = PSA ß Is correct? > > White area = NPSA ß Is correct? > > > So, the real blue and red areas would be (not sure): > > > (Redarea * PSA) / Total surf = Real Red area > > (Bluearea * PSA) / Total surf = Real Blue area > > So: > > Bluearea = 1554.6792 > > Redarea = 2554.3208 > > > Is this calculation correct? > > > Could I apply these calculations to compare them with other proteins of the same family? > > For example: > > Protein members of the immunoglobulin family. > > > > In the Chimera version 1.14, I Download the following programs pdb2pqr-windows-bin64-2.1.1 > > apbs1.5_win64 > > Downloaded from the website: http://www.poissonboltzmann.org > > Next, I assign charges and radii with the following parameters of PDB2PQR > > > <image.png> > And I saved the file. Pqr > > > <image.png> > Later I opened the file 001_B4.pqr with Chimera 1.14 > > > <image.png> > I use the following command: > > > surface > > And run the APBS interface with the following default parameters: > > <image.png> > > As a result, the color gradient of the molecular surface appeared as shown: > > > <image.png> > <image.png> > > > However, my question is: > > Are these parameters correct using the force field PARSE of PDB2PQR? Or, is it necessary to use a different force field? > > > Could I apply the scripts: > > -blue_area_03.py > > -cornflowerblue_area_03.py > > -goldenrod_area_02.py > > -red_area_02.py > > > to calculate the redarea and bluearea and compare it with other proteins? > > > Is there a script that gives me the correct areas of both red and blue colors? > > > Sorry for my long email, as I am new to this area. And I really need help. > > I apologize for so many questions. > > I would greatly appreciate your help. > > > Best regards, > > Fer. > > > > > <blue_area_03.py><red_area_02.py><goldenrod_area_02.py><cornflowerblue_area_03.py>

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How to analyze cryo-EM reconstruction map of virus and prepare publishable figures?
by sunyeping 11 Sep '19

11 Sep '19

Dear all, I am new to cryo-EM structural biology. Now I have a cryo-EM reconstruction map for a virus particle. I wish to analyze the characteristics of the virus, such as the h, k and t number, the component of an cryo-EM asymmetric unit of the capid and prepare some publishable figures. I have no idea how to do these things. Could all these be done with Chimera? Is there any tutorials or manual for these calculation, visualization and drawing? If you could recommend some ways by which I can learn to do these, I would be greatly grateful. Best regards

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