Interaction of antitumour agent mitoxantrone with poly[d(G-C)]--a circular dichroic study

Area of Science:

• Biochemistry
• Molecular Biology
• Drug Discovery

Background:

• Antitumour drug mitoxantrone is a synthetic anthracenedione derivative.
• Synthetic polynucleotides like poly[d(G-C)] serve as models for DNA interactions.
• Understanding drug-DNA binding is crucial for developing targeted cancer therapies.

Purpose of the Study:

• To investigate the binding mechanism of mitoxantrone to the synthetic polynucleotide poly[d(G-C)].
• To characterize the chiroptical properties induced by this drug-nucleotide interaction.
• To elucidate the stages and nature of mitoxantrone-DNA complex formation.

Main Methods:

• Circular dichroic (CD) titrations were employed to study the drug-nucleotide interaction.
• Spectroscopic analysis was performed to observe changes in optical properties.
• Drug-to-nucleotide ratios were systematically varied to identify different binding modes.

Main Results:

• Mitoxantrone binding to poly[d(G-C)] induced significant chiroptical properties in both visible (688 nm) and ultraviolet (260, 320 nm) regions.
• The interaction proceeded in two distinct stages, differentiated by drug/nucleotide ratios below and above 0.11.
• A cooperative enhancement of visible induced circular dichroism (ICD) was observed in the second stage of interaction.

Conclusions:

• Mitoxantrone exhibits complex binding behavior with synthetic DNA, leading to induced chirality.
• The observed two-stage interaction suggests distinct binding modes or conformational changes.
• The cooperative enhancement of ICD indicates a significant structural reorganization upon higher drug loading.