I do not understand your question. Can you tell us what you mean?
If you insert a precursor with a chemical formula into your Skyline document, you will get multiple transitions for the precursor corresponding to the monoisotopic, M+1, etc. masses, depending on what your "Isotope Peaks Included" setting at "Settings > Transition Settings > Full Scan".
It sounds like you must be asking about something else.
-- Nick |