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Updated: May 3, 2026

Simultaneous Affinity Enrichment of Two Post-Translational Modifications for Quantification and Site Localization
Published on: February 27, 2020
New approach for pseudo-MS(3) analysis of peptides and proteins via MALDI in-source decay using radical recombination
Daiki Asakawa1, Nicolas Smargiasso, Edwin De Pauw
1Chemistry Department, Mass Spectrometry Laboratory and GIGA-R, University of Liege , 4000 Liege, Belgium.
Abstract:
Matrix-assisted laser desorption ionization in-source decay (MALDI-ISD) is a useful method for top-down sequencing of proteins and preferentially produces the c'/z(•) fragment pair. Subsequently, radical z(•) fragments undergo a variety of radical reactions. This work is focused on the chemical properties of the 1,5-diaminonaphthalene (1,5-DAN) adducts on z fragment ions (zn*), which are abundant in MALDI-ISD spectra. Postsource decay (PSD) of the zn* fragments resulted in specific peptide bond cleavage adjacent to the binding site of 1,5-DAN, leading to the preferential formation of y'n-1 fragments. The dominant loss of an amino acid with 1,5-DAN from zn* can be used in pseudo-MS(3) mode to identify the C-terminal side fragments from a complex MALDI-ISD spectrum or to determine missed cleavage residues using MALDI-ISD. Although the N-Cα bond at the N-terminal side of Pro is not cleaved by MALDI-ISD, pseudo-MS(3) via zn* can confirm the presence of a Pro residue.
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