Force-Activated DNA Substrates for In Situ Generation of ssDNA and Designed ssDNA/dsDNA Structures in an...

Area of Science:

• Biophysics
• Molecular Biology
• Biochemistry

Background:

• Single-molecule force spectroscopy is crucial for studying biomechanical interactions of DNA-binding proteins.
• Current methods for preparing DNA substrates, particularly those with single-stranded DNA (ssDNA) segments, are often inefficient and time-consuming.
• Efficient substrate preparation is vital for advancing the understanding of DNA unwinding, binding, and wrapping proteins.

Purpose of the Study:

• To develop and detail an improved protocol for constructing force-activated DNA substrates.
• To enable more efficient generation of complex DNA substrates for biophysical studies.
• To facilitate precise biomechanical probing of protein-DNA interactions.

Main Methods:

• Engineered a double-stranded DNA (dsDNA) molecule with a specific GC content sequence between two nicks.
• Utilized optical trapping to apply force (~65 pN) and induce DNA overstretching.
• Achieved controlled dissociation of an ssDNA segment by pulling the engineered dsDNA substrate.

Main Results:

• Developed a method for the efficient construction of force-activated DNA substrates.
• Successfully generated ssDNA segments up to 1000 nucleotides in length.
• Created complex substrates, including a DNA hairpin adjacent to an ssDNA segment.

Conclusions:

• The described protocol significantly enhances the efficiency of force-activated DNA substrate preparation.
• The new substrates are suitable for studying a range of DNA-interacting proteins, including helicases.
• This method advances the capabilities of single-molecule force spectroscopy for biomechanical analyses.