Dear Chimera-Developers, I am a new user and I am amazed of chimeras great functionality! I had some problem with adding hydrogens to a iron-sulfur center containing protein. The Cys ligating the iron got protonated. I was wondering if there is an option to define additional bonds which would help to guide the hydrogen placeing algorithm, which seems to work extremely well otherwise. Also an option to delete or add atoms (particularly hydrogens) would be nice for non-standard protonation states. This might be extensible to some molecular editor, but I guess this would be a major change/new module to the program. Also some function would be nice to optimize the hydrogen bond network (either simple minimization or better some global optimization). Maybe some of the features I am looking for are there, but I couldn't find them yet... :-) Thanks for the great program! Timm Essigke