The physics of DNA stretching

Abstract

Recent progress in experimental micromanipulation techniques allows single biomolecules, such as DNA, to be mechanically distorted under controlled conditions. As well as providing a wealth of new biochemical information, these experiments are also driving advances in statistical physics and non-equilibrium thermodynamics as theorists extend well established statistical methods to include a description of complex biomolecules at the single molecule level. This article will describe the physical ideas that are necessary to understand the wide range of experiments that stretch individual DNA molecules. These experiments operate in three distinct time regimes relative to thermal noise and therefore require three different branches of physics to understand them. Experiments, which stretch long DNA helices, are well described by equilibrium thermodynamics up until the point at which the molecule is irreversibly distorted, where non-equilibrium ideas apply. Short DNA sequences are only marginally stable at room temperature, therefore their response to an external force is dominated by thermal effects. These experiments are able to probe the kinetics of thermally activated processes in biomolecules in more detail than has been previously possible.

Acknowledgments

Many thanks to Sukina Natarajan for kindly reading the manuscript and to Geoffrey Wells for his invaluable help with the figures.

Notes

Sarah Harris has been a research assistant in the condensed matter physics group at University College, London since receiving a PhD in computational biophysics from the University of Nottingham in 2001. Her research interests include the development of computer simulation techniques to model non-equilibrium processes in both physics and biology and extending the traditional methods of statistical physics to provide a description of complex biological systems.

Additional information

Notes on contributors

Sarah Anne Harris

Sarah Harris has been a research assistant in the condensed matter physics group at University College, London since receiving a PhD in computational biophysics from the University of Nottingham in 2001. Her research interests include the development of computer simulation techniques to model non-equilibrium processes in both physics and biology and extending the traditional methods of statistical physics to provide a description of complex biological systems.