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Computer modeling of the tetrasaccharide nystose
A D French1, N Mouhous-Riou, S Pérez
1Southern Regional Research Center, New Orleans, Louisiana 70179.
Carbohydrate Research
|September 2, 1993
Summary
Molecular modeling of nystose reveals distortions in its oligosaccharide linkages, likely due to crystal packing forces rather than inherent conformational preferences. These findings highlight that higher oligosaccharide structures may not reflect isolated disaccharide conformations.
Area of Science:
- Carbohydrate Chemistry
- Computational Chemistry
- Structural Biology
Background:
- Nystose is a tetrasaccharide composed of glucose and three fructose units.
- Understanding the conformational flexibility of oligosaccharides is crucial for their biological function and chemical properties.
Purpose of the Study:
- To model the structure of nystose using computational methods.
- To investigate the influence of crystal packing on nystose conformation.
- To compare the conformations of nystose in crystalline form versus theoretical global minima.
Main Methods:
- Rigid-residue program PFOS modeling.
- Molecular mechanics (MM3) calculations with a dielectric constant of 4.
- Analysis of crystalline nystose trihydrate structure.
Main Results:
- The three furanose rings of crystalline nystose trihydrate are conformationally constrained within 1 kcal.mol-1.
- Intramolecular forces have minimal influence on individual disaccharide segments in the extended crystalline conformation.
- Distortions were observed in the central inulobiose and sucrose linkages, attributed to crystal packing and potential exoanomeric effect miscalculations.
- Conformations of inulobiose linkages in crystalline nystose differ between central and terminal positions.
Conclusions:
- Crystal packing forces significantly influence the observed conformations of higher oligosaccharides like nystose.
- The conformational preferences of isolated disaccharides may not accurately predict the structures of larger oligosaccharides in the solid state.
- Computational modeling combined with crystallographic data provides insights into the complexities of oligosaccharide structure determination.