Bonds vs. Pseudobonds

Hello again! I have a structure containing Germanium bonded to three oxygens and one methyl group. By default, all of the bonds between Germanium and its valences are considered as pseudobonds and hence drawn as such. In the manual, I read that Chimera uses an algorithm that considers atoms classically bonded if the distance is below the sum of their VDW radii (plus a margin of 0.4 A). However, no matter what I set the radius of the Ge atom to (setattr a radius xy Ge), I can't get Chimera to display a regular bond between Ge and its valences. Can you give me a hint how to set a rule when a normal bond is drawn, or how I can draw one manually? Thank you very much, Thomas

Hi Thomas, I would recommend against adding regular covalent bonds between the metal and its coordinating atoms since Chimera's atom-typing code isn't designed to handle coordination covalent bonds, so any chemistry- related computations (hydrogen addition, charge assignment, etc.) involving the complex would be wacky afterward. I would instead recommend you just get the pseudobonds depicted however you prefer. You can do this by control-clicking one of the pseudobonds to select it, then hit up arrow to select all the pseudobonds in all complexes in the molecule, then bring up the Selection Inspector (by clicking the green button at the lower right of the Chimera window). In that you can change the color of the pseudobonds, whether then are depicted as wire or stick, etc. If you change to the "Pseudobond Group" item of the dialog's "Inspect" menu, you can change the line dashing of the pseudobonds. The group also has a color, which is used for any pseudobond whose individual color is "No color". There is also limited control as to how metal complexes look in new models in the "New Molecules" preference category (Favorites-
Preferences). If you must create regular bonds to the metal for some reason there are two methods. You can control double-click a pseudobond and choose "Select Bonded" from the popup menu, then type "bond sel" in the command line -- or you can bring up the Pseudobond Panel with General Controls->Pseudobond Panel and choose the coordination complexes and hit the "select bonded" button, then use Structure Editing->Build Structure, choose the Add/Delete Bonds tab and click the Add button (with the menu set to "reasonable bonds").
--Eric Eric Pettersen UCSF Computer Graphics Lab http://www.cgl.ucsf.edu On Mar 24, 2009, at 9:31 AM, Dipl.-Ing. Thomas Mitterfellner wrote:
Hello again!
I have a structure containing Germanium bonded to three oxygens and one methyl group. By default, all of the bonds between Germanium and its valences are considered as pseudobonds and hence drawn as such. In the manual, I read that Chimera uses an algorithm that considers atoms classically bonded if the distance is below the sum of their VDW radii (plus a margin of 0.4 A). However, no matter what I set the radius of the Ge atom to (setattr a radius xy Ge), I can't get Chimera to display a regular bond between Ge and its valences.
Can you give me a hint how to set a rule when a normal bond is drawn, or how I can draw one manually?
Thank you very much,
Thomas _______________________________________________ Chimera-users mailing list Chimera-users@cgl.ucsf.edu http://www.cgl.ucsf.edu/mailman/listinfo/chimera-users
participants (2)
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Dipl.-Ing. Thomas Mitterfellner
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Eric Pettersen