Examination of surface-bound Ku-DNA complexes in an aqueous environment using MAC mode atomic force microscopy

Area of Science:

• Biophysics
• Molecular Biology
• Nanotechnology

Background:

• Understanding signal-transducing elements is crucial for biosensor development.
• Atomic Force Microscopy (AFM) utilizes a tip as a signal-transducing element.
• Tip-sample interactions can perturb surface-bound molecules.

Purpose of the Study:

• To investigate the influence of tip-sample interactions on measured DNA repair protein (Ku) height.
• To determine how Ku's association with DNA affects its measured height using AFM.
• To analyze the impact of incubation conditions on DNA-Ku complex formation.

Main Methods:

• Atomic Force Microscopy (AFM) was employed to image Ku molecules on a mica surface in aqueous solution.
• Tip-sample interactions were analyzed in the context of measuring protein height.
• Varying incubation times and concentrations were used to study DNA-Ku complex formation.

Main Results:

• The measured height of the Ku protein was significantly influenced by its association with DNA.
• AFM imaging revealed that tip-sample interactions affect the apparent height of Ku.
• Incubation conditions (time and concentration) altered the number and type of observed DNA-Ku complexes.

Conclusions:

• AFM tip-sample interactions are a critical factor in accurately measuring the dimensions of surface-bound proteins like Ku.
• The presence and binding of DNA to Ku substantially alter its measurable height.
• Optimizing incubation conditions is essential for studying DNA-protein interactions using AFM.