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.