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Structures of quinoxaline antibiotics
G M Sheldrick1, A Heine, K Schmidt-Bäse
1Institut für Anorganische Chemie der Universität Göttingen, Germany.
Acta Crystallographica. Section B, Structural Science
|December 1, 1995
Summary
This study determined the crystal structures of echinomycin 2QN and triostin C, revealing subtle differences in their molecular conformations compared to triostin A. These findings offer insights into quinoxaline antibiotic structure-activity relationships.
Area of Science:
- Structural Biology
- Crystallography
- Medicinal Chemistry
Background:
- Quinoxaline antibiotics like echinomycin and triostin are known for their DNA-binding properties.
- Understanding their precise three-dimensional structures is crucial for elucidating their mechanism of action.
Purpose of the Study:
- To determine and compare the crystal structures of echinomycin 2QN, triostin C, and different forms of triostin A.
- To investigate how molecular conformations relate to DNA complex formation and biological activity.
Main Methods:
- X-ray crystallography was employed to determine the atomic structures of the antibiotics in crystalline states.
- Crystal data, including unit cell parameters and space groups, were collected and analyzed.
- Structure refinement was performed using anisotropic refinement with geometrical and displacement parameter restraints.
Main Results:
- The crystal structures of echinomycin 2QN and triostin C were determined, alongside a re-refinement of triostin A.
- Deviations from ideal symmetry were observed due to chromophore folding or ester plane rotation, impacting molecular conformation.
- Intermolecular hydrogen bonding and chromophore stacking patterns were identified, mimicking DNA intercalation.
Conclusions:
- Subtle conformational variations exist among these quinoxaline antibiotics in the crystalline state.
- These structural differences, including disulfide bridge chirality inversion in DNA complexes, influence their interaction with biological targets.
- The crystal packing and hydrogen bonding provide models for understanding antibiotic-DNA interactions.