Infrared Spectroscopy of Mobility-Selected H⁺-Gly-Pro-Gly-Gly (GPGG)

Abstract

Abstract. We report the first results from a new instrument capable of acquiring infrared spectra of mobility-selected ions. This demonstration involves using ion mobility to first separate the protonated peptide Gly-Pro-Gly-Gly (GPGG) into two conformational families with collisional cross-sections of 93.8 and 96.8 Å 2 . After separation, each family is independently analyzed by acquiring the infrared predissociation spectrum of the H 2 -tagged molecules. The ion mobility and spectroscopic data combined with density functional theory (DFT) based molecular dynamics simulations confirm the presence of one major conformer per family, which arises from cis/trans isomerization about the proline residue. We induce isomerization between the two conformers by using collisional activation in the drift tube and monitor the evolution of the ion distribution with ion mobility and infrared spectroscopy. While the cis-proline species is the preferred gas-phase structure, its relative population is smaller than that of the trans-proline species in the initial ion mobility drift distribution. This suggests that a portion of the trans-proline ion population is kinetically trapped as a higher energy conformer and may retain structural elements from solution.

Cryogenic Vibrational Spectroscopy Provides Unique Fingerprints for Glycan Identification

“…1, in which we couple cryogenic, messenger-tagging spectroscopy in an ion trap with drift-tube IMS-MS [22]. …”

“…Both ion mobility spectrometry and cryogenic ion spectroscopy have shown that ions can adopt multiple stable conformations in the gas phase, some of which may be kinetically trapped [22, 30–33]. For this reason, we choose to anneal all the conformations produced in the nano-ESI process, driving them to the lowest energy gas-phase structure(s) before measuring the CCS and the vibrational spectrum (see supporting information).…”

“…One possibility is to add a spectroscopic dimension to IMS-MS to achieve this discrimination, as was recently demonstrated for peptides [22]. Along these lines, Hernandez et al [23] combined differential IMS (DIMS) with infrared multi-photon dissociation (IRMPD) spectroscopy to study mono-hydrated, methylated monosaccharides.…”

Infrared spectrum and structure of the homochiral serine octamer–dichloride complex

“…[22][23][24] Further, IM-MS can be used to prepare samples for gas-phase IR spectroscopy. [25][26][27][28][29] Here ions are simultaneously mass-tocharge (m/z) selected by MS and specific oligomers are geometrical size selected by IMS. This is in contrast to experiments where only m/z selection is used which can suffer from signal overlap between a cluster and its larger counterpart, which, for example, have twice the mass and twice the charge.…”

Fundamentals of Trapped Ion Mobility Spectrometry Part II: Fluid Dynamics

“…In the past few decades, several advances coupling drift tube IMS and other time-dispersive methods (i.e., traveling wave IMS) to mass spectrometry (MS) [1][2][3][4][5][6][7][8][9][10] have extended its versatility for a range of chemical [11][12][13][14][15][16][17], physical [18][19][20][21][22][23], and biomolecular structural studies [24][25][26][27][28][29][30][31][32][33]. Still relatively new to the biomedical field, several groups have recently begun to incorporate LC-IMS-MS workflows in proteomics studies [34][35][36][37], and enhanced performance has been demonstrated [38].…”