Using large statistics, unfolding of ubiquitin under constant force displayed nonexponential dwell-time distribution, which was explained in terms of a form of glassy transition between the folded and unfolded states. This means that the unfolding process occurs over a distribution of activation barriers, and thus can be best described as a disordered process, and characterized with a stretched exponential (Weibull) distribution. Considering unfolding as a diffusion driven process over an activation barrier, we studied protein unfolding under constant force by attaining the timeaveraged mean square displacements (TA-MSD) of the unfolding dwell time distributions within the framework of continuous time random walks (CTRW). To this end, we measured the unfolding dwell-time distributions of I91 protein using atomic force microscopy under a constant force of 180 pN, which similarly to ubiquitin exhibited nonexponential unfolding behavior. According to the CTRW approach, unfolding can be represented by a joint probability density function P(x,t) that can describe the transition over several length or time scales. Using asymptotic algebraic (power-law) decay with a long time behavior of the form ~t –α–1 proves to be more suitable to describe the observed dwell-time distribution. The TA-MSDs alluded to weak ergodicity breaking, and a long-tail power-law dependency of the unfolding dwell-time distributions with an exponent of α ~ 0.85, with a cutoff set by experimental limitation.
|State||Published - 2019|
|Event||JOINT 12th EBSA congress and 10th ICBP – IUPAP congress - Madrid, Spain|
Duration: 20 Jul 2019 → 24 Jul 2019
|Conference||JOINT 12th EBSA congress and 10th ICBP – IUPAP congress|
|Period||20/07/19 → 24/07/19|