A method for the production of a serine ADP-ribosylated protein or peptide comprising preparing an aqueous buffered solution comprising 5 to 60 mM, preferably 10 to 60 mM of a buffer and having a pH between 5.0 and 9.0, preferably between 5.5 to 8.5, and most preferably between 6.1 to 8.3, said solution further comprising
- (a) 0.2 to 2.5 mM NAD+,
- (b) at least 50 nM, preferably 50 to 3000 nM PARP-1, PARP-2 or the PARP-1 variant E988Q,
- (c) at least 100 nM, preferably 100 to 5000 nM HPF1,
- (d) at least 10 μg/mL, preferably 10 μg/mL to 200 μg/mL sonicated DNA, said sonicated DNA preferably comprising DNA fragments of 10 to 330 bp, and
- (e) up to 600 μM protein or peptide, said protein or peptide comprising at least one serine,
- thereby generating a reaction mix, in which the protein or peptide becomes serine ADP-ribosylated.