The Flexibility of Oligosaccharides Unveiled Through Residual Dipolar Coupling Analysis.

Ana Poveda,Peter H Seeberger,Giulio Fittolani,Martina Delbianco,Jesús Jiménez-Barbero

doi:10.3389/fmolb.2021.784318

Abstract

The intrinsic flexibility of glycans complicates the study of their structures and dynamics, which are often important for their biological function. NMR has provided insights into the conformational, dynamic and recognition features of glycans, but suffers from severe chemical shift degeneracy. We employed labelled glycans to explore the conformational behaviour of a β(1-6)-Glc hexasaccharide model through residual dipolar couplings (RDCs). RDC delivered information on the relative orientation of specific residues along the glycan chain and provided experimental clues for the existence of certain geometries. The use of two different aligning media demonstrated the adaptability of flexible oligosaccharide structures to different environments.

Highlights

Saccharides known as glycans, carbohydrates, or sugars are ubiquitous molecules in Nature, that serve in a large variety of roles, from plant cell construction and energy storage to mediation of key biomolecular recognition events (Varki et al, 2017)
The presence of five ω torsional degrees of freedom in the glycan backbone provides high flexibility to the saccharide chain that may adopt a variety of conformations
The results clearly show that the alignment medium is not inert and provides interactions with the molecule

Summary

INTRODUCTION

Saccharides known as glycans, carbohydrates, or sugars are ubiquitous molecules in Nature, that serve in a large variety of roles, from plant cell construction and energy storage to mediation of key biomolecular recognition events (Varki et al, 2017) Despite their chemical similarity, glycan functions largely vary depending on the monosaccharide composition (i.e., relative stereochemistry), as well as on the regio- and stereochemistry of the glycosidic linkages (Gao and Chen, 2020; Gim et al, 2021). Residual dipolar couplings (RDCs) deliver information on the relative orientation of specific X-Y bonds between NMR-active nuclei (Tjandra and Bax, 1997) When these bonds are distributed along a molecule, the global analysis of RDC values may generate valuable information on the global molecular shape and/or assess the presence of a particular conformation (Bax and Grishaev, 2005).

RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT