Dynamic force spectroscopy of the digoxigenin-antibody complex

Area of Science:

• Biophysics
• Biotechnology
• Surface Science

Background:

• Non-covalent interactions, such as the digoxigenin-antibody complex, are crucial for immobilizing samples in single-molecule force measurements.
• Atomic Force Microscopy (AFM) and optical traps are common tools for these measurements.

Purpose of the Study:

• To investigate the mechanical stability of a single digoxigenin-antibody bond using dynamic AFM spectroscopy.
• To assess the impact of single bond rupture on measurement reliability and to propose improved immobilization strategies.

Main Methods:

• Dynamic Atomic Force Microscopy (AFM) spectroscopy was employed to measure the rupture forces of single digoxigenin-antibody bonds.
• The Bell-Evans model was used to analyze the loading rate dependence of bond rupture, considering two unbinding barriers.

Main Results:

• A single digoxigenin-antibody bond exhibits a high probability of failure even at moderate loading rates.
• The study identified two distinct energy barriers for unbinding, with specific widths and spontaneous rates.
• A discrepancy was observed between the predicted and measured rupture force distributions, suggesting non-Markovian unbinding dynamics.

Conclusions:

• Single digoxigenin-antibody bonds are not robust for sample immobilization in force spectroscopy due to their susceptibility to rupture.
• Multiple antibody-antigen bonds are recommended to ensure stable immobilization and reliable measurement outcomes.
• The unbinding process displays complex behavior, including non-Markovian contributions, requiring further investigation.