Introducing structural flexibility into porphyrin-DNA zipper arrays

Area of Science:

• Supramolecular Chemistry
• Nucleic Acid Chemistry
• Biophysical Chemistry

Background:

• DNA-based nanostructures offer precise control over molecular assembly.
• Porphyrin-zipper arrays are promising for advanced materials.
• Linker flexibility is crucial for DNA-based construct stability and function.

Purpose of the Study:

• To synthesize and characterize novel DNA-based porphyrin-zipper arrays using flexible nucleotide building blocks.
• To investigate the impact of linker flexibility on DNA duplex stability and porphyrin electronic interactions.
• To explore post-synthetic metallation of porphyrins and its effect on complex stability and structure.

Main Methods:

• Synthesis of modified 2'-deoxyuridine with a propargyl amide linker.
• Circular Dichroism (CD) spectroscopy to study electronic interactions and stability.
• Molecular modeling to predict porphyrin orientation in DNA.
• Metallation of porphyrins with zinc, cobalt, and copper.
• Small-Angle X-ray Scattering (SAXS) for structural determination.

Main Results:

• A flexible propargyl amide linker increased DNA duplex stability compared to a rigid acetylene linker.
• CD spectra indicated linker-dependent electronic interactions between porphyrins.
• Molecular modeling revealed significant variations in porphyrin orientation within the DNA major groove.
• Post-synthetic metallation with Zn, Co, and Cu was successful, with varying complex stability.
• SAXS showed a dominant two-to-four helical bundle assembly at higher concentrations (≥50 μM).

Conclusions:

• Flexible nucleotide linkers enhance the stability and tunability of DNA-porphyrin arrays.
• Metallation offers a route to functionalize these arrays, though metal stability varies.
• Concentration-dependent self-assembly into helical bundles influences the overall structure in solution.