METABOLITES OF ERWINIA .11. ON THE COLLISION-ACTIVATED FRAGMENTATION OF PROFERRIOXAMINES - EVIDENCE FOR A SUCCINIMIDE-MEDIATED MECHANISM

The fragmentation mechanism of acyclic proferrioxamines has been studi ed by tandem mass spectrometry in a triple stage quadrupole mass analy zer by using activation in the collision cell as well as in the high p ressure region prior to the first mass analyzer. The data suggest that proferrioxamines fragment preferentially at the hydroxamate bonds via cyclic rearrangement to succinimide derivatives. This pattern was obs erved most clearly for the peracetyl derivatives, in which the influen ce of terminal functional groups was masked. Free amino or carboxylic acid functions may modify this basic fragmentation pattern. Using hydr ogen-deuterium exchange, we also were able to show that the hydrogen a toms that are ''recruited'' in the formation of ammonium ions are ''ac idic'' ones from elsewhere in the molecule or the matrix. At the same time, this rules out that they originate from ''activated'' methylene groups, as previously proposed [de Hoffmann, E.; Stroobant, V. Biol. M ass Spectrom. 1991, 20, 142].