MALDI-TOF MS analysis of the extracellular polysaccharides released by the diatom Thalassiosira pseudonana

The extracellular polysaccharides (ECPS) released by diatoms have significant roles in marine ecosystems and have potential applications including drug-discovery and biopharmaceutical precursors. In this study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) technology was used in the structural analysis of the ECPS released by Thalassiosira pseudonana (Bacillariophyta). Three different deproteinization methods, the Sevag method, the trichloroacetic acid (TCA) method, and the enzymolysis method, were compared in the purification of ECPS. Our results suggested that TCA was the best deproteinization method among the three methods for subsequent MALDI-TOF MS investigation because of its high ECPS yield, protein removal ability and reliable MALDI-TOF MS fingerprint. The degree of polymerization (d.p.) profiles, the molecular weight of the ECPS and the distribution pattern of the polymers with different molecular mass were described from the MALDI-TOF MS spectra. This work represents the whole-level composition of the ECPS released by the diatom and has improved our knowledge of the structural characterization of ECPS.