Hi Tom,
If you think specific new model building capabilities would be helpful given the above limitations, explain them and we will be happy to consider them.
For the beginning, I think the following "model building" capabilities would make Chimera even more useful (some of them are maybe already implemented, I do not know Chimera so well yet): 1) Move atom, move selection of atoms, delete selection/atom. Add atoms. 2) Change atom to another one. 3) Add/attach functional groups from library 4) I work in the field of nucleic acids, it would be nice one could build the "ideal" structure (B-DNA, A-DNA, Z-DNA) from sequence (if needed, I can provide a references to papers publishing geometry parameters). Possibly change of pseudorotation angle in deoxyribose and ribose. I am sure other Chimera users would take a benefit if them too. Of course you're right more sophisticated capabilities would probably require force field implementation, and I understand this is (unfortunately) not the direction Chimera is heading to. Regards Dan -- Daniel Svozil, PhD Institute of Organic Chemistry and Biochemistry Center for Biomolecules and Complex Molecular Systems http://www.molecular.cz/~svozil Czech Republic phone: +420-220 410 312