spectra was made on the parent compounds.
2.3. MALDI-TOF/TOF
MALDI–MS spectra were measured on a MALDI-TOF/TOF ultraFLEX III mass spectrometer (Bruker-Daltonics, Bremen, DE). Positive/negative spectra were calibrated externally using the monoisotopic [M+H]+ or [M−H]− ions of PepMixII calibrant (Bruker-Daltonics). -Cyano-4-hydroxycinnamic acid (5mg/mL) in 50% CH3CN/0.1% TFA was used as a MALDI matrix. A 0.4L of sample dissolved in MeCN was premixed with 0.5L of the matrix solution on the target and allowed to dry at ambient temperature