Matrix-assisted laser desorption/ionization mass spectrometry of acidic glycoconjugates facilitated by the use of spermine as a co-matrix

Negative-ion matrix-assisted laser desorption/ionization mass spectra of sialylated glycoconjugates were acquired employing 2,5-dihydroxybenzoic acid (DHB) in conjunction with spermine as a co-matrix. The addition of spermine to DHB permitted an improved crystal formation as well as a higher analyte solubility. Moreover, DHB/spermine appears to minimize alkali adduct formation, thus allowing the sample analysis without desalting. The combined matrix permitted the analysis of complex sialylated and sialylated/fucosylated structures down to the femtomole range. The ability to use such a matrix also facilitates determination of the sialic acid linkages (in combination with a specific enzyme cleavage). The matrix also appears suitable for studies on gangliosides.