FIGURE 5.

Mass spectrometric detection of CMP-Neu5Ac in a moss extract (A) compared to the measurement of a CMP-Neu5Ac standard (B). Extracted ion chromatogram (EIC, m/z 613.1 ± 0.1) of LC-MS measured extract of line GMC5 (A) or 70 pmol of a CMP-Neu5Ac standard (B), respectively (upper panels). In both measurements, peaks corresponding to the [M-H]^–-ion of CMP-Neu5Ac of m/z 613.1 could be detected on MS¹ level (middle panels). Confirmation of corresponding MS¹-peak identities (indicated by the black arrows) was performed on MS² level via the identification of the [M-H]^–-CMP-fragment ion of m/z 322.0 (lower panels). The additional peak in the MS² spectrum of the moss extract compared to the measurement of the CMP-Neu5Ac standard is considered to originate from an unknown compound with a mass similar to the selected CMP-Neu5Ac parent ion. CMP-Neu5Ac-concentration in GMC5 was determined via peak area integration in comparison to defined standard values and resulted in 58 nmol/g DW.