Gas‐phase fragmentation study of biotin reagents using electrospray ionization tandem mass spectrometry on a quadrupole orthogonal time‐of‐flight hybrid instrument

In this study, we evaluated, by electrospray ionization mass spectrometry (ESI‐MS) and collision‐induced dissociation tandem mass spectrometry (CID‐MS/MS) using a quadrupole orthogonal time‐of‐flight (QqToF)‐MS/MS hybrid instrument, the gas‐phase fragmentations of some commercially available biotinyl reagents. The biotin reagents used were: psoralen‐BPE 1, p ‐diazobenzoyl biocytin (DBB) 2 , photoreactive biotin 3 , biotinyl‐hexaethyleneglycol dimer 4 , and the sulfo‐SBED 5 . The results showed that, during ESI‐MS and CID‐MS/MS analyses, the biotin reagents followed a similar gas‐phase fragmentation pattern and the cleavages usually occurred at either end of the spacer arm of the biotin reagents. In general we have observed that the CID‐MS/MS fragmentation routes of the five precursor protonated molecules obtained from the biotin linkers 1 – 5 afforded a series of product ions formed essentially by similar routes. The genesis and the structural identities of all the product ions obtained from the biotin linkers 1 – 5 have been assigned. All the exact mass assignments of the protonated molecules and the product ions were verified by conducting separate CID‐MS/MS analysis of the deuterium‐labelled precursor ions. Copyright © 2009 John Wiley & Sons, Ltd.