2.7. MALDI-TOF-MS analysis
The MALDI-TOF-MS analysis was performed using a Bruker Reflex III MALDI-TOF mass spectrometer (Bruker, Bremen, Germany).
The irradiation source was a pulsed nitrogen laser with a wavelength of 337 nm and the duration of the laser pulse was 3 ns.
In the process of deionization with Amberlite IRP-64 cationexchange resin and selection Cs+ (CsCl, 1.52 mg/mL) as the cationization reagent, the MALDI-TOF mass spectra of fractions FE, FW, and F1–F4 were recorded in reflectron modes with an acceleratingvoltage of 20.0 kV and a reflectron voltage of 23.0 kV (Zhou et al., 2010).