Thiophene-based diamidine forms a "super" at binding minor groove agent

Area of Science:

• Medicinal Chemistry
• Structural Biology
• Molecular Biology

Background:

• The DNA minor groove is a critical site for protein interactions, including enzymes and transcription factors.
• Developing small molecules that target the DNA minor groove is a key strategy in drug discovery and molecular biology research.

Purpose of the Study:

• To design and synthesize novel diamidine derivatives with potential biological activity.
• To investigate the DNA interaction profiles of these derivatives using biophysical and structural methods.

Main Methods:

• Systematic synthesis of diamidine derivatives.
• DNA binding affinity studies using biosensor-Surface Plasmon Resonance (SPR).
• DNA interaction analysis via DNase I footprinting and X-ray crystallography.

Main Results:

• A phenyl-thiophene-benzimidazole derivative exhibited over a 10-fold increase in affinity for the minor groove at AT-rich sequences compared to the parent phenyl-furan-phenyl diamidine.
• Individual modifications (furan to thiophene or phenyl to benzimidazole) did not yield similar affinity enhancements.
• X-ray crystallography revealed that subtle changes in bond angles (C-S-C vs. C-O-C) in the thiophene and benzimidazole moieties significantly altered the positioning of terminal amidines, enhancing DNA interaction strength.

Conclusions:

• The specific combination of thiophene and benzimidazole moieties in diamidine derivatives is crucial for high-affinity DNA minor groove binding at AT sequences.
• Structural insights from X-ray crystallography explain the enhanced binding, highlighting the importance of precise molecular geometry for DNA interaction.