Detecting substrates of kinases by labeling them is an important technique as well as future goal in profiling novel kinases with important biological activity.
In this method, dansyl-ATP has been used as a co-substrate for kinases. The dansyl group is transferred to the substrate peptides and detected by MALDI-TOF. The authors further extend the method to FRET detection of dansyl-labeled substrates that have fluorophores attached to them.
The general idea seems to be be to use gamma-phosphate modified ATP analogues which are accommodated in many kinase active sites. Dansylation is an old and well-known method for peptide sequencing.
Keith D. Green, Mary Kay H. Pflum (2009). Exploring Kinase Cosubstrate Promiscuity: Monitoring Kinase Activity through Dansylation ChemBioChem, 10 (2), 234-237 DOI: 10.1002/cbic.200800393