Activated PARP cleaves NAD+ to nicotinamide and ADP-ribose and polymerizes the ADP-ribose on nuclear acceptor proteins such as histones, transcription factors, and PARP itself. Biotinylated NAD+ (6-Biotin-17-NAD+) provides a non-isotopic alternative to radiolabeled NAD+ for assays requiring this substrate. Biotinylated NAD+ can be used as an indirect measure of PARP activity when biotin incorporation is detected using a streptavidin detection system. Biotinylated NAD+ is also useful for labeling or purifying proteins via poly (ADP)ribosylation.