Tuning porphyrin/DNA supramolecular assemblies by competitive binding

Area of Science:

• Biophysical Chemistry
• Molecular Biophysics
• Supramolecular Chemistry

Background:

• DNA-porphyrin adducts are crucial for photodynamic therapy and molecular electronics.
• Controlling porphyrin aggregation on DNA is essential for tuning their photophysical properties.

Purpose of the Study:

• To investigate the use of an intercalating, non-aggregating porphyrin (AuT4) to modulate the aggregation of a strongly aggregating porphyrin (t-H2Pagg) bound to DNA.
• To establish a method for controlling porphyrin aggregation on a DNA template.

Main Methods:

• Formation of DNA-porphyrin adducts using a strongly aggregating porphyrin (t-H2Pagg).
• Addition of an intercalating, non-aggregating porphyrin (AuT4) to the preformed adducts.
• Analysis of aggregation using Circular Dichroism (CD) and Resonance Light Scattering (RLS) spectroscopy.

Main Results:

• The extent of t-H2Pagg aggregation was successfully controlled by the addition of AuT4.
• The size and intensity of Induced Circular Dichroism (ICD) and RLS signals showed a linear dependence on the concentration of the intercalating dye (AuT4).
• Aggregation signals decreased significantly with increasing available DNA binding sites, indicating template-dependent control.

Conclusions:

• The intercalating porphyrin AuT4 acts as an effective modulator of aggregation for strongly aggregating porphyrins on DNA.
• This strategy allows for fine-tuning of porphyrin aggregation states and their associated photophysical properties on a DNA template.
• The findings provide a novel approach for designing functional DNA-porphyrin supramolecular systems.