Anion sensor-based ratiometric peptide probe for protein kinase activity.

A new fluorescent sensor consisting of Cd(II)-cylcen appended aminocoumarin and a substrate peptide for protein kinase A (PKA) has been designed. Upon phosphorylation by PKA, the metal complex moiety binds to a phosphorylated residue, which in turn displaces the coumarin fluorophore, and this event results in ratiometric change of excitation spectrum in neutral aqueous solution.