Improved method for fluorescence labeling of sugar chains with sialic acid residues.

The pyridylamination methodis useful for the structural analysis of sugar chains from small amountsof glycoproteins. About 60% of the sialyl linkage was, however hydrolyzed under the reaction conditions reported previously.1>2) The growing need for fluorescence labeling oi sialyl sugar chains prompted us to re-investigate the reaction conditions. Recently, we tried pyridylamination conditions under which sialic acid residues were not released, but the yield of pyridylamino (PA-) sugar chains was low.3 4) Here, an improved procedure for the pyridylamination of sialyl sugar chains is described. The yield of PA-sugar chains was almost quantitative, and desialyl-