Molecular tools for the study of ADP-ribosylation: a unified and versatile method to synthesise native mono-ADP-ribosylated peptides Por Voorneveld, J, Rack, JGM, van Gijlswijk, L, Meeuwenoord, NJ, Liu, Q, Overkleeft, HS, van der Marel, GA, Ahel, I, Filippov, DV