Differentiation and sequencing of three constitutional isobaric 18-mer DNA oligomers using low-energy collision tandem mass spectrometry

摘要

In this manuscript we present the differentiation and sequencing of three constitutional isobaric 18-mer DNA oligomers, namely: GATTCATAGCTACGAATC 1, AATTCGTAGCTACGAATC 2, and AATTCGTACCTACGAATG 3 using electrospray ionization-mass spectrometry with a hybrid QqToF-MS/MS instrument. The conventional single scan ESI-QqTOF-MS analyses of the DNA oligomers afforded the same series of deprotonated molecular ions. Low-energy collision tandem mass spectrometric analyses (CID-MS/MS) were used to differentiate and to sequence the three DNA oligomers. Different CID-MS/MS analyses of the various deprotonated molecules: [M-8H]~(8-) at m/z 683.9881 and [M-9H] ~(9-) at m/z 607.8775 were acquired for each 18-mer DNA oligomer. It was established that we could distinguish two different types of diagnostic product ions: (a) the product ions formed by identical cleavage sites within each precursor anion, having the same isobaric masses and (b) the product ions formed by identical cleavage sites, but having different masses. These specific diagnostic product ions facilitated the characterization of each isobaric 18-mer DNA oligomer. In addition, we also indicate that a series of product ions were common for at least two constitutional isobaric 18-mer oligomers. The Mongo Oligo Software was used exclusively to perform the characterization and the correct sequencing of each isobaric DNA oligomer.