Equilibrium free energies from non-equilibrium trajectories with relaxation fluctuation spectroscopy

Recent advances in non-equilibrium statistical mechanics and single-molecule measurements have enabled the determination of equilibrium free energies from non-equilibrium work measurements for fluctuating systems ranging from biological molecules to quantum oscillators. However, for many important n...

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Bibliographic Details
Published in:Nature physics 2018-08, Vol.14 (8), p.842-847
Main Authors: Ross, David, Strychalski, Elizabeth A., Jarzynski, Christopher, Stavis, Samuel M.
Format: Article
Language:English
Subjects:
631/57/2265
631/57/2282
639/766/530/2804
Atomic
Biomolecules
Classical and Continuum Physics
Complex Systems
Condensed Matter Physics
Deoxyribonucleic acid
DNA
Equilibrium
Fluidics
Mathematical and Computational Physics
Molecular
Nanofluids
Optical and Plasma Physics
Oscillators
Physics
Physics and Astronomy
Statistical mechanics
Theoretical
Thermal relaxation
Trajectory analysis
Variation
Work measurement
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Summary:Recent advances in non-equilibrium statistical mechanics and single-molecule measurements have enabled the determination of equilibrium free energies from non-equilibrium work measurements for fluctuating systems ranging from biological molecules to quantum oscillators. However, for many important non-equilibrium processes, it is difficult or impossible to apply and measure the work required to drive the system through the relevant conformational changes. Here, we show that it is possible, with an appropriate extrapolation to infinite temporal scale and zero spatial scale, to determine equilibrium free energies, without work measurement, by analysing the stochastic trajectories of single biomolecules or other nanoscale, fluctuating systems as they spontaneously relax from a non-equilibrium initial state. We validate the method with simulations and demonstrate its application by determining the free-energy profile for DNA molecules in a structured nanofluidic environment with an experimental protocol that mimics many natural processes with energy injection followed by thermal relaxation. Non-equilibrium physics grants access to equilibrium free energies from the work performed on fluctuating systems—but only when the work itself is measurable. Relaxation fluctuation spectroscopy provides an alternative route to these energies.
ISSN:1745-2473
1745-2481
DOI:10.1038/s41567-018-0153-5