Induced circular dichroism in nucleic acid-acridine derivative complexes

Area of Science:

• Biophysical Chemistry
• Molecular Biology
• Pharmacology

Background:

• 9-aminoacridines are a class of compounds with potential therapeutic applications.
• Understanding their interaction with nucleic acids is crucial for drug development.
• Nucleic acid structure and dynamics can be modulated by small molecule binding.

Purpose of the Study:

• To investigate the binding interactions between 9-aminoacridines and various nucleic acids.
• To characterize the spectral changes upon complex formation.
• To elucidate the role of drug structure, specifically cationic side chains, in binding affinity and mode.

Main Methods:

• Visible absorption spectroscopy to detect spectral shifts and new absorption bands.
• Circular Dichroism (CD) spectroscopy to analyze conformational changes and binding modes.
• Complexation studies involving calf thymus DNA, poly(rA).poly(rU), and poly(rI).poly(rC) with quinacrine, acranil, and 9-amino-6-chloro-2-methoxy acridine.

Main Results:

• Complexes formed between nucleic acids and 9-aminoacridines exhibited distinct visible absorption and induced Circular Dichroism (CD) spectra.
• A novel absorption band at longer wavelengths was observed for poly(rA).poly(rU) complexes.
• Induced CD spectra varied significantly among different nucleic acid-drug combinations, indicating diverse binding interactions.

Conclusions:

• The cationic side chains of quinacrine and acranil are critical determinants of their binding properties to DNA and poly(rA).poly(rU).
• Spectral analysis provides insights into the molecular mechanisms of drug-nucleic acid interactions.
• These findings contribute to the rational design of novel nucleic acid-targeting agents.