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New conformational constraints in isotopically (13C) enriched oligosaccharides
M J Milton1, R Harris, M A Probert
1Centre for Biomolecular Sciences, University of St. Andrews, Fife, United Kingdom.
Glycobiology
|March 14, 1998
Summary
Advanced NMR techniques reveal the "anti" conformation of a key trisaccharide linkage. This study enhances understanding of glycan structures and dynamics using isotopic enrichment and molecular simulations.
Area of Science:
- Carbohydrate Chemistry
- Structural Biology
- Nuclear Magnetic Resonance Spectroscopy
Background:
- Glycans play crucial roles in biological processes.
- Understanding glycan conformation is essential for elucidating their functions.
- Resonance overlap in proton NMR complicates structural analysis of complex carbohydrates.
Purpose of the Study:
- To assign resonances and analyze the conformation of 13C-enriched Neu5Acalpha2-3Galbeta1-4Glc.
- To demonstrate the utility of 3D ROESY-HSQC experiments for glycan structural determination.
- To establish a Karplus-type relation for 13C-13C coupling constants in glycans.
Main Methods:
- Multidimensional heteronuclear Nuclear Magnetic Resonance (NMR) spectroscopy.
- Carbon-13 (13C) isotopic enrichment (>95%) of the trisaccharide.
- Three-dimensional Rotating-frame Overhauser Effect SpectroscopY-Heteronuclear Single Quantum Coherence (ROESY-HSQC) experiments.
- 5 ns molecular dynamics simulations.
Main Results:
- 3D ROESY-HSQC provided crucial through-space distance restraints unobtainable by 1H NMR.
- The
- anti
- conformation of the Galbeta1-4Glc glycosidic linkage was unambiguously identified.
- Trans-glycosidic 1H-13C and 13C-13C coupling constants were measured, leading to a derived Karplus-type relation.
- 15 conformational restraints were obtained and validated against molecular dynamics simulations.
Conclusions:
- Heteronuclear NMR, particularly 3D ROESY-HSQC, is powerful for complex glycan structural analysis.
- 13C isotopic enrichment facilitates detailed conformational studies of glycans.
- The study provides valuable insights into the solution-state conformation of Neu5Acalpha2-3Galbeta1-4Glc.
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