Stretching DNA to twice the normal length with single-molecule hydrodynamic trapping

Area of Science:

• Biophysics
• Nanotechnology
• Molecular Biology

Background:

• Single-molecule force spectroscopy provides insights into molecular motors and cellular mechanics.
• Existing methods have limitations in applying high tensions and simultaneous fluorescence imaging.

Purpose of the Study:

• To develop an advanced, surface-free force spectroscopy assay for probing biomolecule mechanics.
• To investigate the mechanical response of double-stranded DNA (dsDNA) under extreme forces.

Main Methods:

• Developed a high-speed hydrodynamic trap using a microfluidic chip for force application.
• Enabled simultaneous force application and single-molecule fluorescence imaging.
• Applied forces up to 250 pN to dsDNA in a surface-free assay.

Main Results:

• Induced a highly extended dsDNA state with twice the contour length of B-DNA.
• Observed a hyperstretched DNA state, consistent with hypotheses of force-induced extension without intercalators.
• Successfully distinguished hyperstretched DNA from single-stranded DNA using combined force and fluorescence data.

Conclusions:

• High-speed hydrodynamic trapping is a powerful and accessible method for single-molecule force spectroscopy.
• This technique allows probing biomolecule mechanics in previously inaccessible force regimes.
• The study demonstrates the induction of hyperstretched DNA solely through high mechanical force.