The negative ion mass spectra of deprotonated 2,5-diketopiperazines
Date
1996
Authors
Bowie, J.
Wabnitz, P.
Waugh, R.
Eckersley, M.
Dua, S.
Blumenthal, T.
Editors
Advisors
Journal Title
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Volume Title
Type:
Journal article
Citation
International journal of mass spectrometry and ion processes, 1996; 154(3):193-201
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Abstract
Deprotonation of 2,5-diketopiperazine (with HO<sup>-</sup>) can occur either on N (position 1(4)) or on carbon (position 3(6)). The two depotonated forms are interconvertible on collisional activation. The major collision-induced fragmentations of (M - H)<sup>-</sup> ions of substituted 2,5-diketopiperazines are (i) characteristic side-chain losses (e.g. Me<sup>.</sup> for Ala, PhCH<inf>2</inf><sup>.</sup> for Phe, and O = C<inf>6</inf>H<inf>4</inf> = CH<inf>2</inf> for Tyr), which identify the particular 2,5-diketopiperazine, and (ii) an unusual loss of RCHO (R is the substituent, e.g. Me for Ala), which involves initial 1,2 migration of R<sup>.</sup> to the carbon of the adjacent carbonyl group. © 1996 Elsevier Science B.V. All rights reserved.