On-target exoglycosidase digestions/MALDI-MS for determining the primary structures of carbohydrate chains

One method used to determine the primary sequence of oligosaccharides is to digest them with exoglycosidases and analyze the resulting digestion products by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Previous research has demonstrated that these digestions can be performed on the MALDI target. However, the procedure requires the sample to be incubated at elevated temperatures, and complete digestion requires a few hours. We demonstrate new conditions that permit exoglycosidase digestions to be performed on the MALDI target at room temperature within 30 min. Oligosaccharide standards were digested with one or more exoglycosidases to show that the enzymes retain their activity and specificity under these new reaction conditions. Using this method, the primary sequences of carbohydrate chains can be determined in a relatively short amount of time.