FLUORESCENCE OF PHOSPHOTYROSINE-TERBIUM(III) COMPLEXES

Phosphotyrosine, a biologically important protein residue, was investigated for the ability to enhance terbium (Tb3+) fluorescence. Spectroscopic analysis of the Tb3+: phosphotyrosine interaction indicated the development of a new excitation peak at 275 nm and strong Tb+ fluoresence enhancement at 488 and 540 nm that was linear over a range from 0.5 to 100 μM amino acid. Subsequent experiments comparing the ability of phosphotyrosine, phosphothreonine, phosphoserine and 20 other common non-phosphorylated amino acids showed that only phosphotyrosine produced significant Tb3+ fluoresence enhancement. Analysis of various phospho-sugars and nucleotides showed (with the expected exception of GMP) that they produced little or no significant fluoresence enhancement, indicating a further selectiveness for the phosphotyrosine: Tb3+ fluoresence enhancement event. These results establish a basis for the future use of Tb3+ fluoresence enhancement as a unique probe for the investigation of phosphotyrosine residues. © 1990.