Recipe 1.7 - Creating Modification
You want to create Modifications.
A Modification is a labeled Mass that can be added to AminoAcidSequence. There are two ways to build an instance of Modification class, using the constructor with a label and a Mass (NumericMass, Composition and NeutralLoss are Masses)
or using the static factory method parseModification from a string with the following format: (label:)?formula
or the same method without label (in this case the label is the formula)
here is a list of getters
See also Recipe 1.6