The interaction of propidium diiodide with self-complementary dinucleoside monophosphates

Area of Science:

• Molecular Biology
• Biochemistry
• Spectroscopy

Background:

• Investigating drug-nucleic acid interactions is crucial for understanding drug mechanisms.
• Dinucleoside monophosphates represent short nucleic acid sequences relevant to biological processes.
• Quinacrine derivatives and propidium are known DNA-binding agents.

Purpose of the Study:

• To compare the binding affinities and modes of a quinacrine derivative and propidium with dinucleoside monophosphates.
• To elucidate the structural basis for differential binding interactions.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy (1H, 13C) was employed.
• Ultraviolet-visible (UV-Vis) spectroscopy was utilized.
• Studies were performed on dinucleoside monophosphates: CpG, GpC, UpA, and ApU.

Main Results:

• Propidium formed complexes with dinucleosides at low concentrations (10(-4) M), showing a preference for pyrimidine-purine sequences like CpG.
• Propidium likely forms intercalated complexes with CpG, supported by significant spectral changes.
• The quinacrine derivative exhibited negligible interaction with dinucleosides up to 5 x 10(-4) M.
• ApU showed minimal spectral changes, resembling interactions with mononucleotides.

Conclusions:

• Cationic side chains do not significantly hinder complex formation between phenanthridines and dinucleoside monophosphates.
• The weak interaction of the quinacrine derivative is attributed to weaker binding of its acridine ring system compared to propidium's phenanthridine ring system.
• Propidium's binding to CpG suggests intercalation with Watson-Crick hydrogen-bonded dimers.