Highly Sensitive MALDI Analyses of Glycans by a New Aminoquinoline-Labeling Method Using 3-Aminoquinoline/α-Cyano-4-hydroxycinnamic Acid Liquid Matrix

In glycomics, mass spectrometry is an indispensable tool for high throughput analyses. Generally speaking, glycans contain many hydroxyl groups and are more difficult to ionize than peptides. Derivatization of glycans has been useful for increasing sensitivity. However, it takes time to purify and causes loss of sample. Here, we show a highly sensitive aminoquinoline (AQ)-labeling method of glycans on a matrix-assisted laser desorption/ionization (MALDI) target using a liquid matrix 3-aminoquinoline (3-AQ)/alpha-cyano-4-hydroxycinnamic acid (CHCA). It is a rapid procedure and reduces loss of sample material during the reaction process, especially in negative ion mode where 10 amol of monosialylated N-glycan were detected as AQ:labeled molecular ions. In addition, MS/MS of 10 amol of monosialylated N-glycan was achieved.