Analysis of structural heterogeneity of κ/β-carrageenan oligosaccharides from Tichocarpus crinitus by negative-ion ESI and tandem MALDI mass spectrometry

A mixture of oligosaccharides, released with enzymatic digestion from κ/β-carrageenan of the red seaweed Tichocarpus crinitus was investigated. The composition, sequence and sulfation pattern of the oligosaccharide mixture were elucidated by negative-ion electrospray ionization and MALDI potential lift tandem TOF mass spectrometry. It was shown, that oligosaccharide mixture (DP up to 20), produced by κ-carrageenase, contained κ-carrabiose, κ-carratetraose as main components, and set of hybrid oligosaccharides as less abundant components: β → κ, κ → β → κ, β → κ → κ, and minor β → ι → κ, β → β → κ → κ, β → κ → β → κ, κ → β → β → κ, κ → β → κ → κ κ → β → β → β → κ, β → β → κ → β → κ, κ → β → κ → β → κ, κ → β → β → κ → κ. The application of arabinoosazone as a MALDI matrix for negative-ion mode with the addition of l-fucose allowed decreasing the in-source fragmentation. The oligosaccharides of κ/β-carrageenan were shown to maintain an ability to induce of TNF-α and IL-6 secretion of immune cells.