AN02/DNP-hapten unbinding forces studied by molecular dynamics atomic force microscopy simulations

Unbinding forces of a spin-labeled dinitrophenyl (DNP) hapten from the monoclonal antibody AN02 Fab fragment have been studied by molecular dynamics atomic force microscopy (AFM) simulations. In our nanosecond simulations, unbinding was enforced by pulling the hapten molecule out of the binding pocket. From the simulations unbinding forces of the complex have been determined as a function of pulling velocity. Considering activated unbinding and frictional forces, we used a simple model to extrapolate the unbinding forces to the millisecond timescale of single molecule AFM unbinding experiments. For such experiments the simulations suggest an unbinding force of 60±30 pN.