The significance of fuzzy boundaries of the barrier regions in single-molecule measurements of failed barrier crossing attempts

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Main Authors: Berezhkovskii, Alexander M., Makarov, Dmitrii E.
Format: Preprint
Published: 2024
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author Berezhkovskii, Alexander M.
Makarov, Dmitrii E.
author_facet Berezhkovskii, Alexander M.
Makarov, Dmitrii E.
contents A recent experimental study reports on measuring the temporal duration and the spatial extent of failed attempts to cross an activation barrier (i.e., "loops") for a folding transition in a single molecule and for a Brownian particle trapped within a bistable potential. Within the model of diffusive dynamics, however, both of these quantities are, on the average, exactly zero because of the recrossings of the barrier region boundary. That is, an observer endowed with infinite spatial and temporal resolution would find that finite loops do not exist (or, more precisely, form a set of measure zero). Here we develop a description of the experiment that takes finite experimental resolution into account and show how the experimental uncertainty of localizing the point, in time and space, where the barrier is crossed leads to observable distributions of loop times and sizes. Although these distributions generally depend on the experimental resolution, this dependence, in certain cases, may amount to a simple resolution-dependent factor and thus the experiments do probe inherent properties of barrier crossing dynamics.
format Preprint
id arxiv_https___arxiv_org_abs_2405_17620
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle The significance of fuzzy boundaries of the barrier regions in single-molecule measurements of failed barrier crossing attempts
Berezhkovskii, Alexander M.
Makarov, Dmitrii E.
Chemical Physics
Soft Condensed Matter
Biological Physics
A recent experimental study reports on measuring the temporal duration and the spatial extent of failed attempts to cross an activation barrier (i.e., "loops") for a folding transition in a single molecule and for a Brownian particle trapped within a bistable potential. Within the model of diffusive dynamics, however, both of these quantities are, on the average, exactly zero because of the recrossings of the barrier region boundary. That is, an observer endowed with infinite spatial and temporal resolution would find that finite loops do not exist (or, more precisely, form a set of measure zero). Here we develop a description of the experiment that takes finite experimental resolution into account and show how the experimental uncertainty of localizing the point, in time and space, where the barrier is crossed leads to observable distributions of loop times and sizes. Although these distributions generally depend on the experimental resolution, this dependence, in certain cases, may amount to a simple resolution-dependent factor and thus the experiments do probe inherent properties of barrier crossing dynamics.
title The significance of fuzzy boundaries of the barrier regions in single-molecule measurements of failed barrier crossing attempts
topic Chemical Physics
Soft Condensed Matter
Biological Physics
url https://arxiv.org/abs/2405.17620