Compositions and methods for detecting phosphomonoester

1. A method of detecting a phosphomonoester moiety of a target compound, comprising

(a) providing a target compound comprising a carboxylic acid moiety and a phosphomonoester moiety, wherein said target compound comprises a protein;

(b) contacting said target compound with a first carbodiimide compound under conditions for preferential addition of said first carbodiimide compound to said carboxylic acid moiety over said phosphomonoester moiety, thereby forming a carboxyl-protected target compound;

(c) contacting said carboxyl-protected target compound with a second carbodiimide compound and an amine under conditions for addition of said amine to said phosphomonoester moiety, thereby forming a nucleophile-modified phosphate moiety; and

(d) detecting said nucleophile-modified phosphate moiety.

2. The method of claim 1 , wherein said phosphomonoester moiety is attached to an amino acid of said protein.

3. The method of claim 2 , further comprising identifying the type of amino acid that is attached to said nucleophile-modified phosphate moiety.

4. The method of claim 3 , further comprising identifying the primary sequence location of said amino acid that is attached to said nucleophile-modified phosphate moiety.

5. The method of claim 1 , further comprising attaching said target compound to an array and determining the location of said target compound in said array.

6. The method of claim 1 , wherein said carboxylic acid moiety comprises the alpha carboxylic acid moiety of the C-terminal amino acid of said protein, the beta carboxylic acid moiety of aspartate or the gamma carboxylic acid moiety of glutamate.

7. The method of claim 1 , wherein said phosphomonoester moiety is selected from the group consisting of phosphoserine, phosphothreonine, and phosphotyrosine.

8. The method of claim 1 , wherein said protein comprises a fragment of a larger protein and step (a) further comprises separating said fragment from at least one other fragment of said larger protein.

9. The method of claim 8 , wherein step (a) further comprises fragmenting said larger protein.

10. The method of claim 1 , wherein step (a) comprises contacting said protein with a kinase under conditions for adding said phosphomonoester moiety to said protein.

11. The method of claim 1 , wherein said conditions for preferential addition of said carbodiimide compound to said carboxylic acid moiety over said phosphomonoester moiety comprise a pH in the range of 2.0 to 7.5.

12. The method of claim 1 , wherein said conditions for preferential addition of said carbodiimide compound to said carboxylic acid moiety over said phosphomonoester moiety comprise a pH in the range of 4.0 to 6.5.

13. The method of claim 1 , wherein said carbodiimide compound is EDC.

14. The method of claim 1 , wherein said conditions for preferential addition of said carbodiimide to said carboxylic acid moiety over said phosphomonoester moiety form an N-acylurea moiety.

15. The method of claim 1 , wherein said amine comprises a label moiety.

16. The method of claim 15 , wherein said label moiety is selected from the group consisting of a fluorophore, quantum dot, radioactive isotope, colored particle, heavy atom isotope, spin label, magnetic isotope, nanoparticles, chromophore, ligand, receptor, and enzyme.

17. The method of claim 1 , wherein said amine is attached to a solid support.

18. The method of claim 1 , wherein said first carbodiimide compound and said second carbodiimide compound comprise the same molecular species.

19. The method of claim 1 , wherein said first carbodiimide compound is contacted with said target compound and said second carbodiimide compound is contacted with said carboxyl-protected target compound in the same reaction vessel.

20. The method of claim 19 , wherein said first carbodiimide compound and said second carbodiimide compound are simultaneously added to said reaction vessel.

21. The method of claim 6 , wherein said carboxylic acid moiety comprises the alpha carboxylic acid moiety of the C-terminal amino acid of said protein.

22. The method of claim 6 , wherein said carboxylic acid moiety comprises the beta carboxylic acid moiety of aspartate.

23. The method of claim 6 , wherein said carboxylic acid moiety comprises the gamma carboxylic acid moiety of glutamate.

24. The method of claim 7 , wherein said phosphomonoester moiety is phosphoserine.

25. The method of claim 7 , wherein said phosphomonoester moiety is phosphothreonine.

26. The method of claim 7 , wherein said phosphomonoester moiety is phosphotyrosine.

27. The method of claim 15 , wherein said label moiety comprises a fluorophore.

28. The method of claim 15 , wherein said label moiety comprises a radioactive isotope.

29. The method of claim 15 , wherein said label moiety comprises a heavy atom isotope.

30. The method of claim 15 , wherein said label moiety comprises a magnetic isotope.

31. The method of claim 15 , wherein said label moiety comprises a chromophores.

32. The method of claim 15 , wherein said label moiety comprises a ligand.

33. The method of claim 15 , wherein said label moiety comprises a receptor.

34. The method of claim 15 , wherein said label moiety comprises an enzyme.

35. The method of claim 15 , wherein said label moiety comprises a quantum dot.

36. The method of claim 15 , wherein said label moiety comprises a colored particle.

37. The method of claim 15 , wherein said label moiety comprises a spin label.

38. The method of claim 15 , wherein said label moiety comprises a nanoparticle.