Abstract: One aspect of the present invention relates to a method of labeling a peptide or protein comprising a phosphorylated amino acid comprising: a) removing from the peptide or protein the phosphate group via a ?-elimination to form a double bond conjugated to a C?O group; b) reacting the double bond from step a) with a nucleophile comprising a tag on a solid support; and c) removing the solid support from the product of step b) forming the labeled peptide or protein. A second aspect of the invention relates to a solid support comprising a linker and tag between the solid support and a nucleophile, wherein the tag comprises a label.