Experimental evidence of symmetry breaking of transition-path times

Nat Commun. 2019 Jan 4;10(1):55. doi: 10.1038/s41467-018-07873-9.

Abstract

While thermal rates of state transitions in classical systems have been studied for almost a century, associated transition-path times have only recently received attention. Uphill and downhill transition paths between states at different free energies should be statistically indistinguishable. Here, we systematically investigate transition-path-time symmetry and report evidence of its breakdown on the molecular- and meso-scale out of equilibrium. In automated Brownian dynamics experiments, we establish first-passage-time symmetries of colloids driven by femtoNewton forces in holographically-created optical landscapes confined within microchannels. Conversely, we show that transitions which couple in a path-dependent manner to fluctuating forces exhibit asymmetry. We reproduce this asymmetry in folding transitions of DNA-hairpins driven out of equilibrium and suggest a topological mechanism of symmetry breakdown. Our results are relevant to measurements that capture a single coordinate in a multidimensional free energy landscape, as encountered in electrophysiology and single-molecule fluorescence experiments.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA / chemistry*
  • Inverted Repeat Sequences
  • Kinetics
  • Models, Chemical*
  • Models, Molecular
  • Molecular Dynamics Simulation
  • Protein Folding
  • Thermodynamics

Substances

  • DNA