title: Combined use of post-ion mobility/collision-induced dissociation and chemometrics for b fragment ion analysis.
abstract: Although structural isomers may yield indistinguishable ion mobility (IM) arrival times and similar fragment ions in tandem mass spectrometry (MS), it is demonstrated that post-IM/collision-induced dissociation MS (post-IM/CID MS) combined with chemometrics can enable independent study of the IM-overlapped isomers. The new approach allowed us to investigate the propensity of selected b type fragment ions from AlaAlaAlaHisAlaAlaAla-NH2 (AAA(His)AAA) heptapeptide to form different isomers. Principle component analysis (PCA) of the unresolved post-IM/CID profiles indicated the presence of two different isomer types for b4(+), b5(+), and b6(+) and a single isomer type for b7(+) fragments of AAA(His)AAA. We employed a simple-to-use interactive self-modeling mixture analysis (SIMPLISMA) to calculate the total IM profiles and CID mass spectra of b fragment isomers. The deconvoluted CID mass spectra showed discernible fragmentation patterns for the two isomers of b4(+), b5(+), and b6(+) fragments. Under our experimental conditions, calculated percentages of the "cyclic" isomers (at the 95% confidence level for n = 3) for b4(+), b5(+), and b6(+) were 61 (± 5)%, 36 (± 5)%, and 48 (± 2)%, respectively. Results from the SIMPLISMA deconvolution of b5(+) species resembled the CID MS patterns of fully resolved IM profiles for the two b5(+) isomers. The "cyclic" isomers for each of the two-component b fragment ions were less susceptible to ion fragmentation than their "linear" counterparts.
authors.affiliation: Department of Chemistry and Biochemistry, Baylor University Sciences Building, Waco, TX 76798, USA.
authors.forename: Behrooz
authors.initials: B
authors.lastname: Zekavat
authors.forename: Mahsan
authors.initials: M
authors.lastname: Miladi
authors.forename: Christopher
authors.initials: C
authors.lastname: Becker
authors.forename: Sharon M
authors.initials: SM
authors.lastname: Munisamy
authors.forename: Touradj
authors.initials: T
authors.lastname: Solouki
mesh_terms: D000595:Amino Acid Sequence; D007477:Ions / Q000737:chemistry; D007536:Isomerism; D013058:Mass Spectrometry / Q000379:methods*; D010455:Peptides / Q000737:chemistry*; D025341:Principal Component Analysis
chemical_list: D007477:Ions; D010455:Peptides