Uncovering Nonconventional and Conventional Hydrogen Bonds in Oligosaccharides through NMR Experiments and Molecular Modeling: Application to Sialyl Lewis‑X

We
describe the direct NMR detection of a C–H···O
nonconventional hydrogen bond (Hbond) and provide experimental and
theoretical evidence for conventional Hbonds in the pentasaccharide
sialyl Lewis-X (sLeX-5) between 5 and 37 °C in water.
Extensive NMR structural studies together with molecular dynamics
simulations offer strong evidence for significant local dynamics in
the LeX core and for previously undetected conventional
Hbonds in rapid equilibrium that modulate structure. These NMR studies
also showed temperature-dependent 1H and 13C
line broadening. The resulting model emerging from this study is more
complex than a simple rigid core description of LeX-like
molecules and improves our understanding of stabilizing interactions
in glycans.