In the set of filters we designed for adding proteins to the AI-assisted reagent selection platform, Protein Specs, you will find two that at first appear similar, Modification and PTM (post-translational modification). PTM relates specifically to modifications of the protein by (but not exclusively):
You can also filter by which specific residue is modified, for example Lysine 9 of human histone H3.
Modification, however, refers to tags (e.g. His, GST, Fc, etc.), conjugates (e.g. fluorescein, biotin, etc.), or reporter proteins (GFP, alkaline phosphatase, peroxidase) that decorate your protein of interest for purposes related to the experiment.