C49H73N11O13 had been confirmed with the accuracy of 3.1 ppm (the
[M+H]+ ion in MALDI) and 0.1 ppm (the [M+2H]2+ ion, ESI-MS2).
Library searches with ESI spectrum (Fig. 5b) led to the two above-
MFcut-off candidates which are isomeric [Dha7]microcystin-RR
(Fig. 5d) and [D-Asp3]microcystin-RR (Fig. 5f). However, because
of not very high MF values and a few reference spectra of different
demethylmicrocystins-RR including [D-Asp3,E-Dhb7]microcystin-
RR [42] available in the library, from one through three spectra,
we cannot definitely identify the particular isomer and prefer ‘‘demethylmicrocystin-
RR’’ as the result statement.