Detection of Protein Phosphorylation on SDS-PAGE Using Probes with a Phosphate-Sensitive Emission Response

Fluorescent probes for the detection of protein phosphorylation on SDS-PAGE are presented. The probes were designed using a dinuclear metal-chelate phosphate recognition unit and an environmentally sensitive fluorophore. The specificity of the probes is determined by their binding site selectivity toward phosphate ions and the emission response induced by the change in the electrostatic environment of the fluorophore upon binding to a phosphorylated amino acid residue. The staining is fully reversible due to the noncovalent binding of the probe. Gel bands with less than 100 ng of phosphorylated alpha-casein are detectable with the new probes on a normal UV-table without specialized equipment like a laser-based gel scanner or a cooled camera detector.