pCMF, ASIS-0070, is a genetically encodable phosphotyrosine analog, p-carboxymethyl-L-phenylalanine (pCMF, 2-amino-3-[4-(carboxymethyl)phenyl]propionic acid) can be site specifically incorporated into the protein of interest while it is synthesized in vivo in cells expressing an orthogonal tRNA synthetase/tRNA pair (Xie et al. 2007). Reversible phosphorylation in proteins mediates enzyme activity through kinases and phosphatases. Phosphorylation regulates protein function and cellular processing including cell cycle, growth, apoptosis and cell signaling pathways.pCMF can be used to replace phosphotyrosine in order to probe protein regulation (Rust et al. 2014). It has been used to investigate post-translational regulation of DNA repair protein by tyrosine kinase (Honda, 2011). pCMF incorporation (1 mM final concentration) enables analysis of phosphorylation effects on structure-activity relationships, substrate specificity, or protein-protein interactions relative to the wild type using various biochemical methods such as kinetic analysis, photocrosslinking, or co-immunoprecipitation (Rust et al. 2014). pCMF is soluble in water.