Fig. 4.

Multistage tandem mass spectrometry analysis allowing the determination of the structure of the permethylated LLO-released oligosaccharide isolated from the diatom P. tricornutum. ESI-MSⁿ spectra with n = 2 selecting m/z 1413.5 ([M + 2Na]²⁺) as the precursor ion (a), n = 3 selecting m/z 1492.5 ([M + Na]⁺) as intermediate ion (b) and n = 3 with m/z 1682.5 ([M + Na]⁺) as intermediate ion (c) of permethylated Hex₁₁HexNAc₂ derivative) isolated from P. tricornutum. On each panel, the ion selected for the fragmentation analysis is shown with a diamond and its fragmentation pattern is proposed according to Prien et al. [40]. Black square: N-acetylglucosamine; grey circle: mannose, black circle: glucose. The fragment ions are labelled according to the nomenclature of Domon and Costello [41]