Structural evidence for inter-residue hydrogen bonding observed for cellobiose in aqueous solution

Area of Science:

• Carbohydrate Chemistry
• Structural Biology
• Biophysical Chemistry

Background:

• Cellobiose is the fundamental repeating disaccharide unit of cellulose.
• Understanding cellobiose's solution structure is crucial for predicting cellulose properties.
• Previous computational and NMR studies suggested an intramolecular hydrogen bond.

Purpose of the Study:

• To determine the solution structure of cellobiose.
• To provide direct evidence for predicted intramolecular hydrogen bonding.
• To elucidate hydrogen bonding interactions involving the non-reducing ring oxygen.

Main Methods:

• Neutron diffraction with isotopic substitution (NDIS).
• Computational modeling.
• Nuclear Magnetic Resonance (NMR) spectroscopy.

Main Results:

• Direct evidence for an intramolecular hydrogen bond between the HO3 hydroxyl group and the O5' oxygen was observed.
• The O5' oxygen is shared by water and the HO3 hydroxyl group with 50% occupancy each.
• Glycosidic and hydroxymethyl torsional angles are consistent with NMR data and previous findings.

Conclusions:

• The study confirms the presence and nature of a significant intramolecular hydrogen bond in cellobiose solution structure.
• This detailed structural information aids in understanding cellulose assembly and properties.
• The findings reconcile neutron diffraction, computational, and NMR data for cellobiose.