Dynamics of single-stranded DNA tethered to a solid

Area of Science:

• Biophysics
• Materials Science
• Molecular Biology

Background:

• Tethering is crucial for biological and industrial applications, including DNA replication and microarrays.
• Tethering single-stranded DNA (ssDNA) can restrict its conformational flexibility and affect its mechanical properties.
• Understanding these mechanical responses is vital for optimizing tethering-based technologies.

Purpose of the Study:

• To investigate the mechanical response of ssDNA when tethered at both ends.
• To quantify the effects of tethering on ssDNA friction and stiffness.
• To determine how conformational constraints impact ssDNA dynamics.

Main Methods:

• Utilizing two atomic force microscope (AFM) cantilevers to tether ssDNA in aqueous solution.
• Employing thermal motion of cantilevers (near 2 kHz) to drive ssDNA dynamics.
• Analyzing asymmetric cross-correlation of cantilever motion to extract mechanical properties.

Main Results:

• Measured friction of tethered ssDNA is significantly higher than expected for unencumbered ssDNA.
• Observed relaxation time of approximately 30 μs, exceeding previous free-molecule measurements.
• The constrained conformations of tethered ssDNA are responsible for the altered mechanical properties.

Conclusions:

• End-tethering of ssDNA substantially alters its mechanical behavior.
• Conformational restriction due to tethering leads to increased friction and longer relaxation times.
• This study provides insights into the physics of tethered polymers and informs the design of DNA-based devices.