ADP-ribosylation has long been recognised as a key regulator of essential signalling pathways, including the DNA damage response. However, only recent and ongoing technological advances are beginning to make it possible to investigate its distinct forms with molecular precision. Here, we design a 'mono-ADP-ribosylation blocking' strategy to develop sensitive, modular antibodies with high specificity for poly(ADP-ribosyl)ation. During peptide antigen generation, we identify a distinctive mass spe...