| Abstract
| - An unprecedented method of producing molecular radical cations of oligopeptides in the gas phase has beendiscovered. Electrospraying a methanolic mixture of a Cu(II)−amine complex, e.g., CuII(dien)(NO3)2 (wheredien = diethylenetriamine), and an oligopeptide (M) yields the [CuII(dien)M]•2+ ion, whose collision-induceddissociation (CID) produces [CuI(dien)]+ and M•+, the molecular cation of the oligopeptide. Abundant M•+is apparent when the oligopeptide contains both a tyrosyl and a basic residuearginyl, lysyl, or histidyl.These structural requirements are similar to those in the metalloradical enzyme process in photosystem II.Tandem mass spectrometry of M•+ produces fragment ions that are both common to and also different from[M + H]+. The fragmentation chemistry of M•+ and of its products appear to be radical driven.
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