DNA-Directed Fluorescence Switching of Silver Clusters

Area of Science:

• Nanomaterials Science
• Biochemistry
• Spectroscopy

Background:

• Silver clusters (≲30 atoms) exhibit diverse electronic spectra and emission intensities.
• DNA scaffolds can stabilize and influence the optical properties of silver clusters.

Purpose of the Study:

• To investigate how DNA sequence and structure control the transformation of silver cluster optical properties.
• To identify DNA sequences that promote a shift from violet absorption to enhanced blue-green fluorescence.

Main Methods:

• Synthesis and characterization of DNA-silver cluster conjugates.
• Spectroscopic analysis (absorption and emission) to monitor optical property changes.
• Oligonucleotide design and synthesis for systematic sequence variation.

Main Results:

• A DNA sequence (S1-S2) forms violet-absorbing silver clusters with low emission.
• Hybridization with a complementary strand (S2C) transforms the chromophore to blue-green emission (λex ≈ 490 nm/λem ≈ 550 nm) with ~100-fold increased intensity.
• The optimal DNA sequence C4AC4T was identified, with specific roles for adenine, thymine, and cytosine bases.
• DNA structure is influenced by both hybridization and cluster coordination, with the single-stranded form being folded by the cluster.

Conclusions:

• DNA sequence composition, particularly C4X motifs, dictates the formation of fluorescent blue-green silver clusters.
• The DNA scaffold's conformation, influenced by the silver cluster adduct, is crucial for optical properties.
• The DNA host structure and silver cluster adduct structure are interdependent, highlighting a coupled system.