Sensitive Analysis of Oligosaccharides Derivatized with 4-Aminobenzoic Acid 2-(Diethylamino)ethyl Ester by Matrix-assisted Laser Desorption/Ionization Mass Spectrometry

Abstract

A sensitive detection method for oligosaccharides using matrix-assisted laser desorption/ionization mass spectrometry has been developed. The method involves the derivatization of oligosaccharides with 4-aminobenzoic acid 2-(diethylamino)ethyl ester (ABDEAE) by reductive amination, a technique which was initially developed for high-sensitivity detection of oligosaccharides by electrospray ionization mass spectrometry (K. Yoshino, T. Takao, H. Murata and Y. Shimonishi, Anal. Chem. 67, 4028 (1995)). Experiments using a high-mannose-type N-linked oligosaccharide (Man8GlcNAc2) as a model oligosaccharide showed that derivatization with ABDEAE gave 400-, 80-, and 20-fold increases in molecular ion abundance over the underivatized oligosaccharide and the oligosaccharide derivatized with 2-aminopyridine and 4-aminobenzoic acid ethyl ester respectively. ABDEAE-derivatized maltoheptaose could be detected at a level of 10 fmol, which represents a 1000-fold increase in sensitivity over the underivatized oligosaccharide. Moreover, ABDEAE derivatization also allows in-source fragmentation to give the specific ions produced by glycosidic cleavage.