Ionspray (IS) and fast atom bombardment (FAB) positive ionization mass spectrometry (MS) of 1:1 Î²-cyclodextrin (Î²-CD)-melatonin (MLT) host-guest complex allowed the detection of gaseous protonated 1:1 Î²-CD-MLT. Tandem MS collision-induced dissociation (CID) of such protonated 1:1 Î²-CD-MLT species showed the proton (charge) to be retained to a significant extent by the host and by its cage fragmentation products, in spite of the higher proton affinity of MLT with respect to that of Î²-CD. This requires an endothermic guest-to-host proton transfer to occur within the gaseous association. Collisional activation could be accounted for by the promotion of such an endothermic process; however, the proton affinity decrease of the guest determined by the loss of the elements of acetamide, which is a dominant MS dissociation reaction of pure protonated MLT, could also provide a rationale for such an endothermic guest-to-host proton transfer. This proposal parallels the reaction scheme we had previously formulated for the analogous MS and tandem MS behaviour of 1:1 Î²-CD-5-methoxytryptamine inclusion complex with the protonated 5-methoxytryptamine guest undergoing deamination. Copyright Â© 2001 John Wiley & Sons, Ltd.
|Numero di pagine||6|
|Rivista||Journal of Mass Spectrometry|
|Stato di pubblicazione||Published - 2001|
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