Fluorescent labeling of a carboxyl group of sialic acid for MALDI-MS analysis of sialyloligosaccharides and ganglioside.
We developed a modified method enabling stable MALDI-MS analysis and fluorescent detection of sialyl-compounds. The modification involved the amidation of sialic acid (Neu5Ac) at the position of the carboxyl group using the fluorescent reagent, 2-(2-pyridilamino)ethylamine (PAEA). In this study the following sialyl-compounds were amidated, 3'-sialyllactose (3'-SL), 6'-sialyllactose (6'-SL), and ganglioside GM3. Yields of PAEA-3'-SL, PAEA-6'-SL, and PAEA-GM3 were 45%, 60%, and 30%, respectively. The PAEA-amidation enabled fluorescence detection of structural isomers using HPLC and TLC at sensitivity levels as low as pmol. In MALDI-TOF-MS and/or MS/MS analysis in positive ion mode, PAEA-amidation provided the following advantages: suppression of preferential cleavage of Neu5Ac; enhancement of molecular-related ion intensities; simplification of MS spectra; and finally, since PAEA-amidation did not cleave the linkage between sugar and aglycon of sialylglycoconjugate, MALDI-TOF-MS and MS/MS analyses revealed the complete structure of the molecule.
Endo
Shin-ichi
S
Department of Physics, School of Science, Kitasato University, Sagamihara, Kanagawa, Japan.
Morita
Minoru
M
Ueno
Masaki
M
Maeda
Tadakazu
T
Terabayashi
Takashi
T
D000631:Aminopyridines / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D005021:Ethylamines / Q000737:chemistry*; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry*; D005679:G(M3) Ganglioside / Q000032:analysis; D005732:Gangliosides / Q000032:analysis*; D007785:Lactose / Q000031:analogs & derivatives / Q000032:analysis; D019158:N-Acetylneuraminic Acid / Q000737:chemistry*; D009844:Oligosaccharides / Q000032:analysis*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
C534472:2-(2-pyridylamino)ethylamine; C421467:3'-sialyllactose; C403777:6'-sialyllactose; D000631:Aminopyridines; D005021:Ethylamines; D005456:Fluorescent Dyes; D005679:G(M3) Ganglioside; D005732:Gangliosides; D009844:Oligosaccharides; C016735:sialooligosaccharides; D019158:N-Acetylneuraminic Acid; D007785:Lactose