February 2018 - phenixbb - phenix-online.org

Re: [phenixbb] Overlapping ligand-protein side chain density
by van den Bedem, Henry 02 Mar '18

02 Mar '18

If the phe is a gatekeeper, shouldn’t the ligand be refined at partial occupancy; i.e. occupancies not necessarily have to ‘add up’ as you suggest? Maybe this link is helpful too: www.biorxiv.org/content/early/2018/01/24/253419 H From: <phenixbb-bounces(a)phenix-online.org> on behalf of "Phan, Jason" <jason.phan(a)vanderbilt.edu> Date: Wednesday, February 28, 2018 at 1:30 PM To: "phenixbb(a)phenix-online.org" <phenixbb(a)phenix-online.org> Subject: [phenixbb] Overlapping ligand-protein side chain density All, A piece of a ligand and the side chain of a “gate-keeper” Phe occupy the same space with well-defined features observed for both (resolution is 1.7 A). It looks about 50:50. How do you refine both ligand and protein side chain in this case? A couple of phenixbb suggestions for dealing with ligand-ligand overlapping density have been considered. With the first suggestion, the two entities still clashed and moved apart off of their respective densities. The second suggestion is not applicable in this case since the other molecule is not a ligand but part of the protein but it was tested anyway. Although there was no bumping, the occupancies don’t add up, resulting in a big blob of negative density around the ligand piece. ------------------------------ Only two comments: 1. At that resolution, constrained group occupancy refinement should work reasonably well (provided you can model the 2 entities). Then you also do not have clashes between the molecules, because Occ(A)+Occ(B)=1, meaning when one (A) is there, the other one (B) is not. This works with refmac (external keyword file); if you need more sophisticated occupancy re/constraints SHELXL may offer more opportunities. 2. There is no necessity for the two NCS copies of the binding site to look exactly the same (non-equivalent). Maybe there is a good reason/story (accessibility, contacts etc) for one site to be occupied differently than the other one. Best, BR —————————————— Modeling two molecules that occupy overlapping binding sites in a structure simply involves designating them as alternate conformers, with the same chain and residue number, and an occupancy that sums to 1.0. For example, if you have an AMP and an ADP that occupy the same binding site, you would define them as AAMP B 501 BADP B 501 and initially set the occupancies for the atoms in each conformer to the ratio (50:50, 30:70, etc.) that you observe in the density. Refinement in this manner is straightforward in PHENIX. Diana ----------------------------

5 6

Overlapping ligand-protein side chain density
by Phan, Jason 28 Feb '18

28 Feb '18

All, A piece of a ligand and the side chain of a “gate-keeper” Phe occupy the same space with well-defined features observed for both (resolution is 1.7 A). It looks about 50:50. How do you refine both ligand and protein side chain in this case? A couple of phenixbb suggestions for dealing with ligand-ligand overlapping density have been considered. With the first suggestion, the two entities still clashed and moved apart off of their respective densities. The second suggestion is not applicable in this case since the other molecule is not a ligand but part of the protein but it was tested anyway. Although there was no bumping, the occupancies don’t add up, resulting in a big blob of negative density around the ligand piece. ------------------------------ Only two comments: 1. At that resolution, constrained group occupancy refinement should work reasonably well (provided you can model the 2 entities). Then you also do not have clashes between the molecules, because Occ(A)+Occ(B)=1, meaning when one (A) is there, the other one (B) is not. This works with refmac (external keyword file); if you need more sophisticated occupancy re/constraints SHELXL may offer more opportunities. 2. There is no necessity for the two NCS copies of the binding site to look exactly the same (non-equivalent). Maybe there is a good reason/story (accessibility, contacts etc) for one site to be occupied differently than the other one. Best, BR —————————————— Modeling two molecules that occupy overlapping binding sites in a structure simply involves designating them as alternate conformers, with the same chain and residue number, and an occupancy that sums to 1.0. For example, if you have an AMP and an ADP that occupy the same binding site, you would define them as AAMP B 501 BADP B 501 and initially set the occupancies for the atoms in each conformer to the ratio (50:50, 30:70, etc.) that you observe in the density. Refinement in this manner is straightforward in PHENIX. Diana ----------------------------

2 1

Plots of local real-space CC
by Murpholino Peligro 27 Feb '18

27 Feb '18

Dear all I want to get the values for the blue line (i.e. local real-space CC) in the Molprobity multicriterion plot. How can I do that? I want to plot those values with gnuplot. I do not want the whole graph (red and green lines). Thanks Murphy

3 5

hi please unsubscribe me
by Zhenwei Su 27 Feb '18

27 Feb '18

-- Zhenwei Su 4417 Spruce Street, APT 3A Philadelphia, PA 19104 email: zwsuustc(a)gmail.com cell phone: (608) 698-4156

1 0

hi please unsubscribe me
by Zhenwei Su 27 Feb '18

27 Feb '18

-- Zhenwei Su 4417 Spruce Street, APT 3A Philadelphia, PA 19104 email: zwsuustc(a)gmail.com cell phone: (608) 698-4156

1 0

Issues with refinement of cadmium
by Mohammad Khan 27 Feb '18

27 Feb '18

Dear all, I am trying to fit Cd ion in a protein structure using Phenix. However, the refinement transposes CD to DC and returns me a result with DC ( 2'-DEOXYCYTIDINE-5'-MONOPHOSPHATE) in the validation report and gives me the missing atoms accordingly. When I open the same structure in Coot, it shows me the ion Cd. Also, the .pdb file contains Cd. Cd is present in my crystallization condition and fits well into the density. Other metal atoms such as Zn and Cl have refined well. HETATM 5535 CD CD F 1 156.533 -64.594 138.360 1.00 76.11 CD HETATM 5536 CD CD F 2 119.954-111.545 105.562 1.00 35.85 CD HETATM 5537 CD CD F 3 152.936 -93.077 102.747 1.00 28.68 CD HETATM 5538 CD CD F 4 121.467 -96.375 128.574 1.00 72.24 CD Can someone suggest what may be wrong? Thanks in advance!

3 2

[Feature request] Exclude atoms outside user provided mask from refinement (in phenix.real_space_refine)
by Oliver Clarke 26 Feb '18

26 Feb '18

Hi, Often I would like to refine part of a model against a EM map generated by masked refinement. Such a map is typically better than the globally refined map in the region within the mask, and worse outside it. It would be useful to have the capacity to refine the same model first against the globally refined map, and then against the maps generated by masked refinement, but restricting refinement in the latter case to atoms/residues within the bounds of the mask. Is this something that could be maybe added in a future version of phenix.real_space_refine? This would mean allowing the user to provide a mask file, and setting an option to exclude all atoms/residues outside the mask boundaries from refinement. Cheers Oli

1 0

refining a covalent-bound ligand
by Sebastiano Pasqualato 26 Feb '18

26 Feb '18

Hi there, I have a pretty basic question. I am refining a structure in which a drug has been covalently linked to a Cys of the protein. I have generated the .cif fie for the ligand, but I don’t know how to tell the program that carbon C04 has to be covalently linked to the SG of the Cys. Is that sufficient to insert a LINK record in the pdb file? What is the correct syntax for that? Thanks a lot for the feedback and sorry for the naive question, ciao, Sebastiano -- Sebastiano Pasqualato, PhD Crystallography Unit Department of Experimental Oncology European Institute of Oncology IFOM-IEO Campus via Adamello, 16 20139 - Milano Italy tel +39 02 9437 5167 fax +39 02 9437 5990 web http://is.gd/IEOXtalUnit

5 5

Information regarding Anisotropic atoms
by pooja kesari 22 Feb '18

22 Feb '18

I observed that phenix.refine tool is adding anisotropic atoms to the pdb file by default even at resolution more than 2A. Can anyone please suggest why is it doing so?

2 1

lattice symmetry and free-set selection?
by Edward A. Berry 22 Feb '18

22 Feb '18

Where can I find description of the free-r selection parameters: refinement.input.xray_data.r_free_flags { lattice_symmetry_max_delta=5 use_lattice_symmetry=True } ?

1 0