IR-IR Conformation Specific Spectroscopy of Na⁺(Glucose) Adducts

Abstract

We report an IR-IR double resonance study of the structural landscape present in the Na(glucose) complex. Our experimental approach involves minimal modifications to a typical IR predissociation setup, and can be carried out via ion-dip or isomer-burning methods, providing additional flexibility to suit different experimental needs. In the current study, the single-laser IR predissociation spectrum of Na(glucose), which clearly indicates contributions from multiple structures, was experimentally disentangled to reveal the presence of three α-conformers and five β-conformers. Comparisons with calculations show that these eight conformations correspond to the lowest energy gas-phase structures with distinctive Na coordination. Graphical Abstract ᅟ.

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

“…4b and e for species A and B, respectively. Signals in the wavenumber range below 3550 cm -1 can be attributed to strongly hydrogen-bonded OH and NH oscillators, while relatively free OH vibrations are expected to occur from 3600 cm -1 and above [20]. The high sensitivity of IR spectroscopy to smallest structural details are reflected in these spectra.…”

“…A vibrational spectrum will therefore contain information about the structure-defining hydrogen-bonding network within each molecule. Aided by quantum mechanical calculations, IR spectroscopy becomes the ideal method for precise structural analysis of smaller sugar molecules [20][21][22][23][24], with the size-limiting factor being the computational methods available on the one hand and increasingly congested experimental spectra as the molecules become larger on the other. Nevertheless, a vibrational spectrum will always represent a characteristic fingerprint for a given carbohydrate structure.…”

Cryogenic Ion Spectroscopy for Identification of Monosaccharide Anomers

“…We thus applied IR-IR ion dip spectroscopy to acquire vibrational fingerprints of individual conformers (Figure 2). Vibrations of the OH group are expected to appear in the spectral region above 3400 cm -1 , 15 and NH group vibrations usually appear lower than 3400 cm -1 . 28 Fixing the wavenumber of the IR pump pulse on an OH band at 3542 cm -1 and scanning the wavenumber of the probe pulse produces a spectrum with eight bands -more than the total number of stretch vibrations in the molecule -indicating that multiple conformers absorb at this wavenumber ( Figure S4).…”

“…In contrast to protonated glucosamine studied here, sodiated glucose exhibits a larger number of conformers due to strong binding of the coordinating metal to a few hydroxyl groups that hinders the interconversion of conformers. 15,34 The presence of a proton in glucosamine does not hinder the interconversion of conformers as strongly as the coordinating metal.…”

Direct Measurement of the Visible to UV Photodissociation Processes for the PhotoCORM TryptoCORM

“…IR-IR conformer-specific spectroscopy was performed to confirm that only a single isomer is present (Section S4). [43]…”