Target Identification by Diazirine Photo‐Cross‐Linking and Click Chemistry

Abstract Target identification is often the rate‐determining step in deciphering the mechanism of action of biologically active small molecules. Photo‐affinity labeling (PAL) represents a useful biochemical strategy for target identification in complex protein mixtures. This unit describes the use of alkyl diazirine‐based photo‐affinity probes and Cu(I)‐catalyzed click chemistry to covalently label and visualize the targets of biologically active small molecules. A general method for affinity purification of probe‐modified proteins, useful for identification of protein targets, is also described. Curr. Protoc. Chem Biol . 1:55‐73. © 2009 by John Wiley & Sons, Inc.