The sheer number of kinases and phosphoproteins makes the important task of identifying kinase-substrate pairs very difficult. New phophosphoproteins are being identified by proteomic techniques, yet there is currently no robust method for finding a kinase that preformed a particular phosphorylation event. I report in this thesis on such a method that covalently traps a kinase to the corresponding substrate through a crosslinking ATP mimetic to enable identification of upstream kinases by mass spectrometry
