Base-Pair Contents and Sequences of DNA Double Helices Differentiated by Surface-Enhanced Raman Spectroscopy.

Area of Science:

• Spectroscopy
• Biochemistry
• Nanotechnology

Background:

• DNA sequence and conformation are critical for biological function.
• Label-free detection methods are highly desirable for DNA analysis.
• Surface-enhanced Raman spectroscopy (SERS) offers high sensitivity for molecular detection.

Purpose of the Study:

• To develop a direct, label-free method for DNA sequence analysis using SERS.
• To distinguish between different DNA conformations (random coils vs. hairpins).
• To accurately quantify DNA base-pair content and identify sequence-specific mutations.

Main Methods:

• Utilized aluminum-ion-aggregated and iodide-modified silver nanoparticles as SERS substrates.
• Analyzed Raman spectra of DNA strands with varying sequences and conformations.
• Employed a deoxyribose band as an internal standard for spectral normalization.

Main Results:

• Reproducibly enhanced Raman bands were observed upon DNA hybridization, correlating with Watson-Crick hydrogen bonds and hairpin formation.
• Characteristic bands allowed unambiguous differentiation between random DNA conformations and hairpins.
• Accurate measurement of guanine-cytosine base-pair content and sequence in DNA hairpins was achieved.
• A single base mutation in a functional double helix was confidently identified.

Conclusions:

• SERS provides a powerful, label-free approach for direct DNA sequence analysis.
• The method can distinguish DNA secondary structures and quantify base composition.
• This technique holds promise for sensitive mutation detection and genetic analysis.