Following the DNA ligation of a single duplex using atomic force microscopy

Area of Science:

• Biophysics
• Molecular Biology
• Nanotechnology

Background:

• DNA integrity is crucial for genetic stability.
• DNA ligase plays a vital role in DNA repair and replication.
• Atomic force microscopy (AFM) enables visualization and manipulation of single molecules.

Purpose of the Study:

• To investigate the nick-sealing process of a single DNA duplex using AFM.
• To quantify the mechanical changes in DNA upon nick sealing.
• To determine the optimal conditions for DNA nick sealing by DNA ligase.

Main Methods:

• Immobilization of DNA fragments onto an AFM tip and substrate using dendron modification.
• Hybridization of DNA fragments to create a single nicked DNA duplex.
• Application of AFM to measure the unbinding force of the DNA duplex before and after nick sealing by DNA ligase.
• Varying pause times to assess nick-sealing probability.

Main Results:

• A significant increase in unbinding force was observed after nick sealing, from 24.0 ± 4.4 pN to 62.8 ± 14.6 pN.
• A 30-second pause resulted in a 60% nick-sealing probability, higher than a 10-second pause.
• The nick-sealing event could be repeated at different positions in the presence of free DNA fragments.

Conclusions:

• AFM is a powerful tool for studying single DNA nick-sealing events at the molecular level.
• The mechanical properties of DNA change significantly upon successful nick sealing.
• Optimizing reaction times is crucial for efficient DNA repair by DNA ligase.