1 research outputs found
Energy-Resolved Ion Mobility Spectrometry: Composite Breakdown Curves for Distinguishing Isomeric Product Ions
Identification of lipopeptides (LpAA)
synthesized
from bacteria involves the study of structural characterization. Twenty LpAA have been characterized using commercial tandem high-resolution
mass spectrometers in negative electrospray, employing nonresonant
excitation in “RF only” collision cells and generally
behave identically. However, [LpAA-H]− (AA = Asp or Glu) shows surprising fragmentation pathways, yielding
a complementary fatty acid carboxylate and dehydrated amino acid fragment
anions. In this study, the dissociation mechanisms of [C12Glu-H]− were determinate using energy-resolved mass spectrometry
(ERMS). Product ion breakdown profiles are, generally, unimodal with
full width at half-maximum (fwhm) increasing as product ion m/z ratios decrease, except for the two
product ions of interest (fatty acid carboxylate and dehydrated glutamate)
characterized by broad and composite profiles. Such behavior was already
shown for other ions using a custom-built guided ion beam mass spectrometer.
In this study, we investigate the meaning of these particular profiles
from an ERMS breakdown, using fragmentation mechanisms depending on
the collision energy. ERMS on line with ion mobility spectrometry
(IMS), here called ER-IMS, provides a way to probe such questions.
Broad or composite profiles imply that the corresponding product ions
may be generated by two (or more) pathways, resulting in common or
isomeric product ion structures. ER-IMS analysis indicates that the
fatty acid carboxylate product ion is produced with a common structure
through different pathways, while dehydrated glutamate has two isomeric
forms depending on the mechanism involved. Drift time values correlate
with the calculated collision cross section that confirms the product
ion structures and fragmentation mechanisms