Anharmonic simulations of the vibrational spectrum of sulfated compounds: application to the glycosaminoglycan fragment glucosamine 6-sulfate

作者：Barnes Loic; Schindler Baptiste; Allouche Abdul Rahman^*; Simon Daniel; Chambert Stephane; Oomens Jos; Compagnon Isabelle

来源：Physical Chemistry Chemical Physics, 2015, 17(39): 25705-25713.

DOI：10.1039/c5cp02079d

Mid-infrared spectroscopy coupled with mass spectrometry is an appealing tool for the sequencing and structural elucidation of functional modifications in biopolymers, as it offers direct spectroscopic identification of the functionality where the traditional mass spectrometric approach is insufficient. Whereas the gas phase vibrational spectroscopy of peptides (and to a lesser extent saccharides) has been widely investigated, sulfation has attracted much less attention, despite its prevalence in natural polymers. The simulation of the vibrational spectra of such functionalized compounds is however notoriously challenging, which impairs the interpretation of spectroscopic data in terms of structure. Driven by a striking case of such a failure for a sulfated glycosaminoglycan fragment, we elaborate on an original hybrid GVPT2 anharmonic approach. This strategy offers a significantly improved accuracy in the description of the sulfate modes, without the recourse to empirical scaling factors, and with a greatly reduced computational cost which is otherwise prohibitive for molecules of this size. Alternatively, we propose a selection of reasonably accurate harmonic methods with adequate scaling factors optimized on a set of benchmark compounds.

• 出版日期2015