Ion spectroscopy of heterogeneous mixtures: IRMPD and DFT analysis of anomers and conformers of monosaccharides

The gas phase IR spectra of three protonated hexosamines are measured in the 3 mu m range using IRMPD spectroscopy and compared with DFT simulation of the IR spectra to identify the ring conformations and the contributions of the alpha and beta anomers to the experimental spectra. We propose an original approach for the deconvolution and quantification of heterogeneous IR spectra based on linear combination of the DFT spectra. The method is applied to the analysis of a two-component anomeric mixture and validated using NMR analysis. Finally, we further estimate the relative populations of a three-component mixture: the anomers and conformers of glucosamine. (C) 2019 Elsevier B.V. All rights reserved.