Ultrashort Nucleic Acid Duplexes Exhibit Long Wormlike Chain Behavior with Force-Dependent Edge Effects

Area of Science:

• Biophysics
• Nanotechnology
• Molecular Biology

Background:

• Nucleic acids are crucial in biological processes and nanotechnology.
• Understanding their elastic properties at short length scales (<15 nucleotides) is limited.
• Existing models may not fully capture behavior at the nanoscale.

Purpose of the Study:

• To investigate the elastic behavior of short oligonucleotides (7-12 nucleotides) under tension.
• To directly observe and quantify the difference in extension between single-stranded and duplex DNA states.
• To identify deviations from established polymer models at ultrashort length scales.

Main Methods:

• Utilized optical tweezers to apply controlled tension to oligonucleotides.
• Integrated fluorescence imaging for real-time observation of hybridization.
• Measured end-to-end extension differences between single-stranded and duplex DNA states.

Main Results:

• Observed elastic behavior consistent with long-polymer models at low forces (<8 pN).
• Measured extensions were smaller than predicted by models at higher forces (>8 pN).
• Identified sequence-dependent duplex edge effects as the cause for deviations at higher forces.

Conclusions:

• Short nucleic acid elasticity deviates from standard models at higher forces.
• Sequence-dependent duplex edge effects are critical for understanding nanoscale elasticity.
• Findings inform applications in nanotechnology and molecular biophysics.