Guest-to-host proton transfer in melatonin–β-cyclodextrin inclusion complex by ionspray, fast atom bombardment and tandem mass spectrometry

✍ Scribed by David Bongiorno; Leopoldo Ceraulo; Andrea Mele; Walter Panzeri; Antonio Selva; Vincenzo Turco Liveri

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 116 KB
• Volume: 36
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.226

✦ Synopsis

Abstract

Ionspray (IS) and fast atom bombardment (FAB) positive ionization mass spectrometry (MS) of 1 : 1 β‐cyclodextrin (β‐CD)–melatonin (MLT) host–guest complex allowed the detection of gaseous protonated 1 : 1 β‐CD–MLT. Tandem MS collision‐induced dissociation (CID) of such protonated 1 : 1 β‐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 β‐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 β‐CD–5‐methoxytryptamine inclusion complex with the protonated 5‐methoxytryptamine guest undergoing deamination. Copyright © 2001 John Wiley & Sons, Ltd.