Volume 79, Number 5, September 2007
Article Number 58001
Number of page(s) 6
Section Interdisciplinary Physics and Related Areas of Science and Technology
Published online 31 July 2007
EPL, 79 (2007) 58001
DOI: 10.1209/0295-5075/79/58001

Dynamic force spectroscopy of a single condensed DNA

Y. Murayama1, H. Wada2 and M. Sano1

1  Department of Physics, the University of Tokyo - 113-0033 Tokyo, Japan
2  Physics Department, Technical University Munich - 85748 Garching, Germany

received 16 February 2007; accepted in final form 5 July 2007; published September 2007
published online 31 July 2007

The dynamic force vs. the extension relationship of single DNA molecules in the presence of trivalent cation, spermidine, is studied using optical tweezers. A hysteresis between the stretching and relaxing cycles increases with increasing operating speed. The rate-dependent hysteresis is manifested due to the dissipative stretching and the delay of DNA condensation in the relaxing process. Effective friction inside a DNA condensate is estimated quantitatively, and its physical origin is discussed based on the Kramers-type kinetic theory.

87.14.Gg - DNA, RNA.
87.15.He - Dynamics and conformational change.
82.37.-j - Single molecule kinetics.

© Europhysics Letters Association 2007