DNA as UV light-harvesting antenna

Area of Science:

• Biophysics
• Photochemistry
• Nanotechnology

Background:

• DNA's ordered structure and UV chromophores are analogous to photosynthetic light-harvesting complexes.
• Quantum coherence is crucial for efficient energy transfer in natural systems.
• Understanding DNA energy transport is vital for cellular photochemistry and DNA-based nanostructures.

Purpose of the Study:

• To investigate energy transfer mechanisms in DNA complexes.
• To compare energy transfer in DNA with silver nanoclusters versus DNA with acridine orange.
• To determine the extent of exciton delocalization in DNA.

Main Methods:

• Steady-state fluorescence measurements using 15-mer DNA duplex and calf thymus DNA templates.
• Fluorescence up-conversion measurements to determine energy transfer timescales.
• Formation of DNA complexes with silver nanoclusters and acridine orange.

Main Results:

• Excitation energy transferred to silver nanoclusters from 21 and 28 nucleobases in different DNA templates.
• Energy transfer in DNA-acridine orange complexes occurred over only four neighboring bases.
• Energy transfer in silver-DNA complexes occurred within 100 femtoseconds.
• Exciton delocalization observed over at least four to seven stacked bases in silver-DNA complexes.

Conclusions:

• Efficient energy transport in silver-DNA complexes suggests an excitonic mechanism.
• Exciton delocalization in DNA can extend beyond two bases, challenging existing models.
• Findings advance understanding of energy transfer in DNA nanostructures and photochemical processes.