Unfolding force definition and the unified model for the mean unfolding force dependence on the loading rate

TL;DR

This paper clarifies different definitions of unfolding force in single-molecule force spectroscopy, introduces a unified model for mean unfolding force dependence on loading rate, and demonstrates its superior accuracy through simulations.

Contribution

It presents the first comprehensive discussion of three unfolding force definitions and unifies existing DFS models into a single framework applicable across all loading rates.

Findings

Unified model accurately describes mean unfolding force across all loading rates.

Simulations confirm the superiority of the unified model over existing models.

Different definitions of unfolding force impact the interpretation of force spectroscopy data.

Abstract

In single-molecule force spectroscopy experiments, the dependence of the mean unfolding force on the loading rate is used for obtaining information about the energetic and dynamic properties of the system under study. However, it is crucial to understand that different dynamic force spectroscopy (DFS) models are applicable in different regimes, and that different definitions of the unfolding force might be used in those models. Here, for the first time, we discuss three definitions of the unfolding force. We carried out Brownian dynamics simulations in order to demonstrate the difference between these definitions and compare DFS models. Importantly, we derive the dependence of the mean unfolding force for the whole range of the loading rates by unifying three previously reported DFS models. Among the currently available models, this unified model shows the best agreement with the simulated data.