Binuclear Terbium(III) Complex as a Probe for Tyrosine Phosphorylation

By using the luminescence from binuclear complexes of Tb III (Tb 2 -L 1 and Tb 2 -L 2 ), phosphorylated Tyr residue in peptides was selectively detected in neutral aqueous solutions. Neither the non-phosphorylated Tyr, pSer, pThr, nor the other phosphate-containing biomolecules tested affected the luminescence intensity to any notable extent. Upon the binding of the pTyr to these Tb III complexes, the luminescence from the metal ion was notably promoted, as the light energy absorbed by the benzene ring of pTyr is efficiently transferred to the Tb III center. The binding activity of the binuclear Tb III complexes towards pTyr is two orders of magnitude larger than that of the corresponding mononuclear complex. These binuclear complexes were successfully used for real-time monitoring of enzymatic phosphorylation of a peptide by a tyrosine kinase.