Use of bispyridines to improve labeling of nucleophiles
Bispyridines improve the labeling of nucleophiles, including amines and thiols and are particularly useful for improving labeling with acidic and basic labels. Use of bispyridines with such labels dramatically increases labeling compared to protocols without a bispyridine. The labeled nucleophile can then be subjected to standard analytical methods.
1. A method of labeling N-glycans released from a glycoprotein of interest, said method comprising:
(a) incubating said glycoprotein with an enzyme that releases said N-glycans from said glycoprotein as glycosylamines, and
(b) contacting said glycosylamines with a solution comprising a solvent, an amine-reactive label, and a bispyridine, under conditions allowing labeling of said glycosylamines by said amine-reactive label,
thereby labeling said N-glycans released from said glycoprotein with said amine-reactive label.
2. The method of claim 1 , wherein said glycoprotein is an antibody.
3. The method of claim 1 , further wherein said glycoprotein is immobilized on a solid support before step (b).
4. The method of claim 1 , wherein said enzyme is an endoglycosidase.
5. The method of claim 4 , further wherein said enzyme is an amidase.
6. The method of claim 5 , further wherein said amidase is PNG F.
7. The method of claim 1 , wherein said solvent is dimethylforamide or dimethyl sulfoxide.
8. The method of claim 1 , wherein said bispyridine is pyridine, 4,4′-(1,3-propanediyl)bis- or pyridine, 4,4′-(1,2-ethanediyl)bis-.
9. The method of claim 1 , further wherein said labeled glycosylamines are provided to an analytical means.
10. The method of claim 9 , wherein said analytical means is selected from the group consisting of high-pressure liquid chromatography, capillary electrophoresis, microfluidic separation, and mass spectrometry.
11. The method of claim 10 , wherein said analytical means is high-pressure liquid chromatography.
12. The method of claim 10 , wherein said analytical means is mass spectrometry.
13. The method of claim 1 , wherein said bispyridine is pyridine, 4,4′,4″,4′″ (2,3,4,5-thiophenetetrayl)tetrakis; 1,2-Ethanediol, 1,2-di-4-pyridinyl; methanone, di-4-pyridinyl; cyclohexanone, 2,6-bis(4-pyridinylmethylene-,(2E6E)-; 2H-Indol-2-one, 1,3-dihydro-1-phenyl-3,3-bis(4-pyridinylmethyl)-; 2,3-Butanediol, 2,3-di-4-pyridinyl-; 1,2-Ethanediol, 1,2-di-4-pyridinyl-, (1R,2S)-rel-; 9(10H)-Anthracenone, 10,10-bis(4-pyridinylmethyl)-; 2,4,6(1H,3H,5H)-Pyrimidinetrione, 1-(3-methoxyphenyl)-5,5-bis[2-(4-pyridinyl)ethyl]-; 2,4,6(1H,3H,5H)-Pyrimidinetrione, 1,3-dimethyl-5,5-bis[2-(4-pyridinyl)ethyl]-; Ethanone, 1,2-di-4-pyridinyl-; Pyridine, 4,4′-(1,4-butanediyl)bis-; 2,4,6(1H,3H,5H)-Pyrimidinetrione, 1-(phenylmethyl)-5,5-bis[2-(4-pyridinyl)ethyl]-; 2,4,6(1H,3H,5H)-Pyrimidinetrione, 1-(4-ethoxyphenyl)-5,5-bis[2-(4-pyridinyl)ethyl]-; 4-Pyridinepropanenitrile, α-4-pyridinyl-; 1,2-Ethanediarnine, N,N′-dimethyl-1,2-di-4-pyridinyl-(9Cl); pyridine, 4,4′,4″-(1H-irnidazole-2,4,5-triyl)tris-; 4,6(1H,5H)Pyrimidinedione, dihydro-5,5-bis[2-(4-pyridinyl)ethyl]-2-thioxo-; or Pyridine, 4,4′-methylenebis-.