Sialic Acid Linkage Specific Derivatization of Glycosphingolipid Glycans by Ring-Opening Aminolysis of Lactones

Sialic acids occur widely as glycoconjugates at the nonreducing ends of glycans. Glycosphingolipids (GSLs) include a large number of sialyl-linked glycan isomers with alpha 2,3-, alpha 2,6-, and alpha 2,8-linked polysialic acids. Thus, it is difficult to distinguish structural isomers with the same mass by mass spectrometry. The sialic acid linkage specific alkylamidation (SALSA) method has been developed for discriminating between alpha 2,3- and alpha 2,6-linked isomers, but sequential amidation of linkage-specific sialic acids is generally complicated and time-consuming. Moreover, analysis of GSL-glycans containing alpha 2,8-linked polysialic acids using solid-phase SALSA has not been reported. Herein, we report a novel SALSA method focused on ring-opening aminolysis (aminolysis-SALSA), which shortens the reaction time and simplifies the experimental procedures. We demonstrate that aminolysis-SALSA can successfully distinguish serum GSL-glycan isomers by mass spectrometry. In addition, ring-opening aminolysis can easily be applied to amine and hydrazine derivatives.