"*" IN SMILES string

Hello again,





During our normal use of JChem 3.0.12 we appear to have generated a small number of SMILES strings that contain a "*". Can you please explain the significance of a "*" in a SMILES string? What does it code for? Subsequently we are finding that SMILES strings like these are being rejected as invalid by our docking tool of choice - so the question is whether you consider these SMILES to be valid? If not please advise how we might stop them occuring.





Thanks for your help,


Daniel.

Hello!





The symbol `*' ("star") is treated by SMILES as a valid atomic symbol meaning "unspecified atomic number" and is represented as an atom of atomic number zero.





This symbol is generated if you have ANY atom in the molecule (see the attachment).





I hope this helps.





Andras

Thank you Andras,





You learn somthing new every day.





Now you mention it, I do seem to recall * as essentially meaning "attachment point" in MDL project library structures, although I'm not suggesting there the same, the idea is certainly similar.





Cheers,


Daniel.