{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,17]],"date-time":"2025-10-17T00:29:08Z","timestamp":1760660948536,"version":"build-2065373602"},"reference-count":31,"publisher":"Wiley","issue":"12","license":[{"start":{"date-parts":[[2020,11,2]],"date-time":"2020-11-02T00:00:00Z","timestamp":1604275200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["analyticalsciencejournals.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["J Mass Spectrom"],"published-print":{"date-parts":[[2020,12]]},"abstract":"Abstract<\/jats:title>Fragmentation of peptide radical cations [M].<\/jats:sup>+<\/jats:sup> has been examined using matrix\u2010assisted laser desorption\/ionization (MALDI) in\u2010source decay (ISD) with hydrogen\u2010abstracting nitro\u2010substituted matrices. The ISD spectra of peptides containing an arginine (Arg) residue at carboxyl (C)\u2010termini showed preferential [w<\/jats:italic>]+<\/jats:sup> ions when 4\u2010nitro\u20101\u2010naphthol (4,1\u2010NNL) matrix was used, whereas the use of 3,5\u2010dinitrosalicylic acid (3,5\u2010DNSA) resulted in preferential [x<\/jats:italic>]+<\/jats:sup> ions. Minor or some [d<\/jats:italic>]+<\/jats:sup>, [x<\/jats:italic>]+<\/jats:sup>, [y<\/jats:italic>]+<\/jats:sup>, and [z<\/jats:italic>]+<\/jats:sup> ions were also observed. For peptides containing Arg residue at amino (N)\u2010termini, the ISD spectra showed preferential [a<\/jats:italic>]+<\/jats:sup> ions independent of matrix used. The observed [a<\/jats:italic>]+<\/jats:sup>, [w<\/jats:italic>]+<\/jats:sup>, [x<\/jats:italic>]+<\/jats:sup>, [y<\/jats:italic>]+<\/jats:sup>, and [z<\/jats:italic>]+<\/jats:sup> ions can be rationally explained by radical\u2010directed dissociation (RDD) of the peptide radical cations [M].<\/jats:sup>+<\/jats:sup>, although [d<\/jats:italic>]+<\/jats:sup> ions may be formed via Norrish Type I cleavage and\/or by RDD of [M].<\/jats:sup>+<\/jats:sup> ions. The formation of overdegraded [d<\/jats:italic>]+<\/jats:sup>, [w<\/jats:italic>]+<\/jats:sup>, [y<\/jats:italic>]+<\/jats:sup>, and [z<\/jats:italic>]+<\/jats:sup> ions is discussed from the standpoint of the internal energy of radical cations [M].<\/jats:sup>+<\/jats:sup> and radical fragment ions [a<\/jats:italic> + H].<\/jats:sup>+<\/jats:sup> and [x<\/jats:italic> + H].<\/jats:sup>+<\/jats:sup> deposited via collisional interactions with excited matrix molecules in the MALDI plume. The radical site of the peptide cations [M].<\/jats:sup>+<\/jats:sup> was presumed to be backbone amide nitrogen, from MALDI\u2010ISD data with three different deuterated amino acids.<\/jats:p>","DOI":"10.1002\/jms.4668","type":"journal-article","created":{"date-parts":[[2023,9,4]],"date-time":"2023-09-04T10:48:48Z","timestamp":1693824528000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Matrix\u2010dependent a<\/i>\/x<\/i> pair and overdegraded w<\/i>\/y<\/i>\/z<\/i> ions generated by radical\u2010directed dissociation of peptide radical cations [M]+<\/sup> in matrix\u2010assisted laser desorption\/ionization in\u2010source decay"],"prefix":"10.1002","volume":"55","author":[{"given":"Kei","family":"Miyazawa","sequence":"first","affiliation":[{"name":"Mass Spectrometry Laboratory, Graduate School in Nanobioscience Yokohama City University Yokohama 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