Computational and NMR Conformational Analysis of Galactofuranoside Cycles Presented in Bacterial and Fungal Polysaccharide Antigens.

Alexey G Gerbst,Nikolay E Nifantiev,Vadim B Krylov

doi:10.3389/fmolb.2021.719396

Alexey G Gerbst, Nikolay E Nifantiev + Show 1 more

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https://doi.org/10.3389/fmolb.2021.719396

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Abstract

Unlike pyranoside cycles which are generally characterized by strictly defined conformational preferences, furanosides are flexible and may adopt a wide range of available conformations. During our previous studies, conformational changes of galactofuranoside cycles upon total sulfation were described computationally, using a simple Hartree–Fock (HF) method, and principal conformers of the 5-membered galactose ring were revealed. However, in the case of more complex disaccharide structures, it was found that this method and the widely applied DFT-B3LYP produced results that deviated from experimental evidence. In this study, other DFT functionals (PBE0 and double hybrid B2PLYP) along with RI-MP2 are employed to study the conformational behavior of the galactofuranoside ring. Reinvestigation of galactofuranosides with a lactic acid substituent at O-3 revealed that changes in the orientation of lactic acid residue at O-3 might induce conformational changes of the furanoside cycle. Such findings are important for further modeling of carbohydrate–protein interaction.

Highlights

The understanding of the 3D structure of biologically important oligosaccharide sequences and of their conformational mobility is required for the assessment of their immunodeterminant fragments and prediction of the topology of oligosaccharide binding to cellular receptors and lectins (Zhang et al, 2017)
The problem that inspired this investigation first occurred in the study by (Dorokhova et al, 2021) when we started the conformational analysis of model disaccharides 1 and 2
Several DFT and MP2-based methods were compared in modeling of furanoside ring conformations, including ones with a lactic acid substituent

Summary

Introduction

The understanding of the 3D structure of biologically important oligosaccharide sequences and of their conformational mobility is required for the assessment of their immunodeterminant fragments and prediction of the topology of oligosaccharide binding to cellular receptors and lectins (Zhang et al, 2017). In this context, galactofuranoside containing oligosaccharide determinants which are often presented in the antigenic polysaccharide chains of pathogenic bacteria and fungi represents a special interest because of its biological importance (Richards and Lowary, 2009; Krylov and Nifantiev, 2020).

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