October 2020 - IMP-users

Problem with IMP.core.TransformationSymmetry
by Jan Kosinski 07 Dec '20

07 Dec '20

Hi Ben, I tried to test sth related to the TransformationSymmetry on rigid bodies and I fail to get it work properly in the below simple example. In the example I create four copies of a chain, create four-fold symmetry constraints and try to generate the updated configuration using model.update(). In the resulting model.rmf, three chain copies are fine and follow the symmetry but one copy of the chains is weirdly rotated. What do I do wrong? import IMP import IMP.core import IMP.atom import IMP.container import IMP.rmf import RMF import sys IMP.setup_from_argv(sys.argv, "rigid bodies") m = IMP.Model() rbs = [] hs = [] for i in range(4): mp1 = IMP.atom.read_pdb(IMP.core.get_example_path('example_protein.pdb'), m) chains = IMP.atom.get_by_type(mp1, IMP.atom.CHAIN_TYPE) hs.append(IMP.atom.Hierarchy(chains[0])) rbs.append(IMP.atom.create_rigid_body(chains[0])) for i, rb in enumerate(rbs[1:]): # the other 3 particles are all symmetric copies of the first IMP.core.Reference.setup_particle(rb, rbs[0]) # the symmetry operation is rotation around the z axis tr = IMP.algebra.Transformation3D( IMP.algebra.get_rotation_about_axis(IMP.algebra.get_basis_vector_3d(2), 2 * 3.14 / len(rbs) * (i + 1)), IMP.algebra.Vector3D(0, 0, 0)) sm = IMP.core.TransformationSymmetry(tr) c = IMP.core.SingletonConstraint(sm, None, m, rb) m.add_score_state(c) m.update() modelrmf = RMF.create_rmf_file('model.rmf') IMP.rmf.add_hierarchies(modelrmf, hs) IMP.rmf.save_frame(modelrmf) Using IMP 2.13.0. Best, Jan

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SAXS restraint error
by Cameron Murray 21 Oct '20

21 Oct '20

Hi, I am working with the pmi library and I am trying to add an IMP.pmi.restraints.saxs.SAXSRestraint but I am getting an error. The error does not come when I add the restraint and as far as I can tell the system understands what I have given it. The issue arises when I add the restraint to the model and then try to optimize_flexible_beads(), here is the full error: Traceback (most recent call last): File "test.py", line 154, in <module> dof_obj.optimize_flexible_beads(100) File "/usr/local/lib/python3.8/site-packages/IMP/pmi/dof/__init__.py", line 518, in optimize_flexible_beads mc.optimize(nsteps) File "/usr/local/lib/python3.8/site-packages/IMP/pmi/samplers.py", line 201, in optimize self.mc.optimize(nstep * self.get_number_of_movers()) File "/usr/local/lib/python3.8/site-packages/IMP/__init__.py", line 5041, in optimize return _IMP_kernel.Optimizer_optimize(self, max_steps) _IMP_kernel.IOException: Profile is not sampled for q = 0.0131, q_max = 0.5 You can remove points with q > 0.5 from the experimental profile or recompute the profile with higher max_q I dont understand what this means, as I have set the maxq to be 0.3 in the restraint and the profile object has 0.3 as its maxq. q = 0.0131 is my first data point. I also get a similar error if I either remove the optimize_flexible_beads step or add the restraint to the model after optimization and then run replica exchange, here is that error: Traceback (most recent call last): File "test.py", line 172, in <module> rex.execute_macro() File "/usr/local/lib/python3.8/site-packages/IMP/pmi/macros.py", line 395, in execute_macro output.init_stat2(low_temp_stat_file, File "/usr/local/lib/python3.8/site-packages/IMP/pmi/output.py", line 820, in init_stat2 d = l.get_output() File "/usr/local/lib/python3.8/site-packages/IMP/pmi/restraints/__init__.py", line 107, in get_output score = self.evaluate() File "/usr/local/lib/python3.8/site-packages/IMP/pmi/restraints/__init__.py", line 83, in evaluate return self.weight * self.rs.unprotected_evaluate(None) File "/usr/local/lib/python3.8/site-packages/IMP/__init__.py", line 3785, in unprotected_evaluate return _IMP_kernel.RestraintSet_unprotected_evaluate(self, da) _IMP_kernel.IOException: Profile is not sampled for q = 0.0131, q_max = 0.5 You can remove points with q > 0.5 from the experimental profile or recompute the profile with higher max_q It seems like the issue is occuring after I add the restraint so I dont think it is a file format issue but like I said im not sure what is going on. Anything you could do to help would be appreciated. Thanks, Cameron

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Issue with Flexible Modeling Using PMI
by Jake Sumner 21 Oct '20

21 Oct '20

Hello, I have recently been trying to conduct flexible modeling using beads of varying size for a particular protein. I have separated the protein into 5 domains based on the PDB crystal structure, and I have already done rigid body modeling to fit the domains to an EM map we have. However, I seem to run into an issue when I try to do flexible modeling by creating bead models using the topology file. Essentially, each of the domains is coming directly from the PDB crystal structure, and I am creating beads from the residues listed there and in the FASTA file. The beads are created with a varying number of residues to reflect the size and overall flexibility of the domain. When I set up the topology file in this manner, and make sure to not invoke the rigid body or super rigid body options, I get a structure warning from IMP saying it is making the components flexible. However, I also get a warning that "No hierarchies were passed to create_flexible_beads()". I am not sure why no flexible beads are being created from the PDB/FASTA specified residues. I am using the "ToplogyReader" and the "execute_macro" functions to set up the hierarchy and the DOF for the MC simulation. I have tried 'enable_all_movers()' to make the beads flexible, but they don't seem to exist. When I try 'dof.get_flexible_beads()' or 'dof.get_movers()', both of the lists are empty. Because the movers list is empty, I am unable to run the MC simulation macro. Could you possibly help me diagnose this problem? Is there a simple way to do the flexible bead modeling and fit it to an EM map, as I have described above? Is there some consideration I am missing in my script? Thank you, and if you need more information on the errors or the system I am working with, I am happy to provide it. Best, Jacob

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Coarse Grain PDB structure
by Altair Hernández 20 Oct '20

20 Oct '20

Hi IMP users, I would like to know how to coarse a PDB structure using IMP, in a way to represent it as spheres but reducing the level of resolution (each 10 aa grouped and represented as a sphere). I have tried reading the input PDB with IMP.atom.read_pdb to generate the atom hierarchy and with IMP.atom.setup_coarse_secondary_structure_residues, however without success. Should I try using IMP.pmi instead? Thanks! Altair

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Precision for systems with fixed bodies
by Atefeh Rafiei 13 Oct '20

13 Oct '20

Hi there, I have a question regarding the interpretation of the last step of integrative modeling. I am wondering if the precision calculations (for structural clusters) presented in the analysis workflow (from PMI analysis repository on GitHub), will calculate precision for all components of the modeling system including the fixed rigid bodies? I am asking this as I have a good portion of my protein system being fixed in the modeling (for specific reasons), so I am not sure if that will impact the precision I get. Thanks, Atefeh

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