Enhanced Mixture Separations of Metal Adducted Tetrasaccharides Using Frequency Encoded Ion Mobility Separations and Tandem Mass Spectrometry

Abstract

Using five isomeric tetrasaccharides in combination with seven multivalent metals, the impact on mobility separations and resulting CID spectra were examined using a hybrid ion mobility atmospheric pressure drift tube system coupled with a linear ion trap. By enhancing the duty cycle of the drift tube system using a linearly chirped frequency, the collision-induced dissociation spectra were encoded in the mobility domain according to the drift times of each glycan isomer precursor. Differential fragmentation patterns correlated with precursor drift times ensured direct assignment of fragments with precursor structure whether as individual standards or in a mixture of isomers. In addition to certain metal ions providing higher degrees of separation than others, in select cases more than one arrival time distribution was observed for a single pure carbohydrate isomer. These observations suggest the existence of alternative coordination sites within a single monomeric species, but more interesting was the observation of different fragmentation ion yields for carbohydrate dimers formed through metal adduction. Positive-ion data were also compared with negative-ion species, where dimer formation did not occur and single peaks were observed for each isomeric tetrasaccharide-alditol. This enhanced analytical power has implications not only for carbohydrate molecules but also for a wide variety of complex mixtures of molecules where dissociation spectra may potentially be derived from combinations of monomeric, homodimeric, and heterodimeric species having identical nominal m/z values. Graphical Abstract ᅟ.

Separation and Identification of Glycan Anomers Using Ultrahigh-Resolution Ion-Mobility Spectrometry and Cryogenic Ion Spectroscopy

“…We first used a drift-tube IMS instrument coupled to a cryogenic ion trap to measure the collision cross sections (CCS) of isomeric disaccharides prior to their spectroscopic analysis [26,27], however it became evident that the IMS resolution provided by our 2 m drift tube would not be sufficient to resolve most of these species from a mixture. By variation of the charge state of the investigated glycans from protonated to deprotonated [39] or by using different metal ion adducts as charge carriers [40][41][42] it is possible to enhance IMS separation of specific glycan mixtures, however, a generally applicable method has not been established to date. Our approach to separate glycan isomers as completely as possible before spectroscopic interrogation employs a newly constructed instrument in which we combine ultrahighresolution IMS, using structures for lossless ion manipulation (SLIM) [43,44], with a cryogenic ion trap and a time-offlight (TOF) MS to allow messenger-tagging IR spectroscopy of CCS-and m/z-selected glycans [38,45].…”

Adduct-ion formation in trapped ion mobility spectrometry as a potential tool for studying molecular structures and conformations

“…Recently, Morrison, Bendiak, & Clowers [18] investigated the influence of cation adduct formation with tetrasaccharides using atmospheric pressure dual-gate drift ion mobility coupled to a Thermo linear ion trap mass spectrometer. They noticed that for some glycans the coordination of a metal ion lead to formation of dimers, which was observed as a second mobility peak appearing at the same nominal mass as the monomeric form of the analyte.…”

Magnifying ion mobility spectrometry–mass spectrometry measurements for biomolecular structure studies

“…The bottom two traces show data for a low-mobility selection and a comparison with data for the linear glycan isomer. Panels A and B were adapted with permission from figures obtained from references 40 and 44, respectively.…”

“…Morrison et . al examined metalated tetrasaccharides and observed multiple conformers for several species suggesting the presence of multiple coordination sites [44]. Additionally, the ion fragmentation efficiencies of metalated dimers were observed to be dramatically different.…”