question about annealing residues in pdb file
Hello, I have been using chimera extensively for pdb rendering and manipulation. I needed some information that i couldn't find in the archives. I am aware that chimera displays the pdb file according to the co-ordinates mentioned in the pdb file. However in my situation I have changed co-ordinates of some of the secondary structure elements like helices to do a better fit. and I have saved the new coordinates in the same pdb file. So now when i render this pdb file it shows me the structure with the modified orientation, however chimera displays a continuous model. In the sense, the breaks that I had introduced by changing the angles of some of the helices and thus making the linkage discontinuous are somehow annealed by chimera. So my question is what sort of algorithm chimera employs to seal breaks in the pdb structure. The same pdb strucutre when viewed in swiss model deepview software contains gaps/breaks at the junctions where the coordinates of the helices have been modified from the original ones. however no such breaks are seen when displayed through chimera. First I thought chimera does energy minimization to find out the best way to arrange the loops between the helices so as to create the best continuous structure. However it seems that chimera doesn't do energy minimization, yet it's able to display a complete structure. Could you please inform me about how this is accomplished. Thanks Sanket
Hi Sanket, If I am understanding the problem correctly, it's easy to fix; just use the command "longbond". http://www.cgl.ucsf.edu/chimera/docs/UsersGuide/midas/longbond.html Chimera shows the connections because the PDB file (I am guessing) still implies they are there: the residues are in the same chain and don't have TER between them. DeepView probably applies some distance test similar to "longbond" automatically when a structure is opened. I hope this helps, Elaine On Aug 31, 2006, at 1:21 PM, Shah, Sanket S wrote:
Hello, I have been using chimera extensively for pdb rendering and manipulation. I needed some information that i couldn't find in the archives. I am aware that chimera displays the pdb file according to the co-ordinates mentioned in the pdb file. However in my situation I have changed co-ordinates of some of the secondary structure elements like helices to do a better fit. and I have saved the new coordinates in the same pdb file. So now when i render this pdb file it shows me the structure with the modified orientation, however chimera displays a continuous model. In the sense, the breaks that I had introduced by changing the angles of some of the helices and thus making the linkage discontinuous are somehow annealed by chimera. So my question is what sort of algorithm chimera employs to seal breaks in the pdb structure. The same pdb strucutre when viewed in swiss model deepview software contains gaps/breaks at the junctions where the coordinates of the helices have been modified! from the original ones. however no such breaks are seen when displayed through chimera. First I thought chimera does energy minimization to find out the best way to arrange the loops between the helices so as to create the best continuous structure. However it seems that chimera doesn't do energy minimization, yet it's able to display a complete structure. Could you please inform me about how this is accomplished. Thanks Sanket
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----- Elaine C. Meng, Ph.D. meng@cgl.ucsf.edu UCSF Computer Graphics Lab and Babbitt Lab Department of Pharmaceutical Chemistry University of California, San Francisco http://www.cgl.ucsf.edu/home/meng/index.html
participants (2)
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Elaine Meng -
Shah, Sanket S