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Updated: Jul 16, 2026

Self-assembling Morphologies Obtained from Helical Polycarbodiimide Copolymers and Their Triazole Derivatives
Published on: February 7, 2017
Linkage and pyranosyl ring twisting in cyclodextrins
Alfred D French1, Glenn P Johnson
1Southern Regional Research Center, US Department of Agriculture, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, United States. afrench@srrc.ars.usda.gov
Acylated cyclodextrins (CDs) exhibit distortions due to the loss of hydrogen bonds, leading to unique helical geometries. These structural changes are influenced by the exo-anomeric effect and acyl stacking in distorted CDs.
Area of Science:
- Carbohydrate Chemistry
- Structural Biology
- Supramolecular Chemistry
Background:
- Classic cyclodextrins (CDs) possess a doughnut shape stabilized by inter-residue hydrogen bonds.
- Acylated CDs lack these stabilizing hydrogen bonds, leading to structural distortions.
- Understanding these distortions provides insight into the shapes of CDs and potentially starch structures.
Purpose of the Study:
- To investigate the structural distortions in acylated beta-cyclodextrins (beta-CDs).
- To understand the role of the exo-anomeric effect and acyl stacking in stabilizing distorted CD structures.
- To correlate observed distortions with helical geometry and glucose residue twists.
Main Methods:
- Analysis of crystal structure data for acylated beta-CDs and related compounds.
- Examination of energy maps for maltose analogs to assess linkage energies.
- Measurement of glucose ring twists and pseudo torsion angles.
Main Results:
- Acylated beta-CDs exhibit distortions, with some linkages achieving low energies via the exo-anomeric effect and acyl stacking.
- These low-energy linkages induce left-handed helical geometry, counterbalanced by right-handed character in other linkages.
- Significant twists in glucose residues (e.g., +34 degrees in acetylated beta-CD) contribute to the overall helical structure.
Conclusions:
- Distorted structures in acylated CDs arise from the interplay of the exo-anomeric effect, acyl stacking, and macrocyclic constraints.
- The observed helical geometries and glucose ring twists are crucial for accommodating these distortions.
- This study enhances understanding of CD structural flexibility and the factors governing their shapes.
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