Inter-strand cross-links and single-strand breaks produced by gold(I) and gold(III) coordination complexes

Area of Science:

• Inorganic Chemistry
• Biochemistry
• Molecular Biology

Background:

• Gold coordination complexes are explored for their potential interactions with biological macromolecules.
• Understanding the mechanisms of DNA binding and modification by metal complexes is crucial for developing novel therapeutic agents.

Purpose of the Study:

• To investigate the DNA binding and inter-strand cross-linking capabilities of various gold(I) and gold(III) coordination complexes.
• To determine the influence of gold oxidation state and coordinating ligands on DNA interaction.
• To elucidate the effect of thiol-containing agents on gold-DNA complexes and DNA integrity.

Main Methods:

• Fluorescence-based assay using ethidium bromide to detect DNA binding.
• Agarose gel electrophoresis to analyze DNA structural changes and dissociation of gold-DNA complexes.
• Assessment of DNA strand breakage and cross-linking induced by gold complexes and subsequent thiol treatment.

Main Results:

• DNA binding and inter-strand cross-linking by gold complexes depend on ligand type, not gold oxidation state.
• Weakly coordinating ligands facilitate DNA binding, while two or more such ligands are required for cross-linking.
• 2-mercaptoethanol dissociates gold-DNA complexes, regenerates superhelical DNA, and induces DNA strand breakage, particularly in superhelical DNA.

Conclusions:

• The nature of ligands in gold coordination complexes significantly dictates their DNA interaction profile.
• Gold complexes can induce DNA inter-strand cross-links and strand breaks, with potential biological implications for intracellular DNA and chromatin.
• The observed DNA breakage is not oxygen-mediated, suggesting a distinct chemical mechanism.