Model accounting for the effects of pulling-device stiffness in the analyses of single-molecule force measurements

Single-molecule force spectroscopy provides a powerful approach for investigating molecular transitions along specific reaction coordinates. Here, we present a general analytical model for extracting the intrinsic rates and activation free energies from force measurements on single molecules that is applicable to a broad range of pulling speeds and device stiffnesses. This model relaxes existing limitations to perform force measurements with soft pulling devices for proper theoretical analyses and, in fact, allows experiments to specifically exploit device stiffness as a control parameter in addition to pulling speed for a reliable estimation of energetic and kinetic parameters.