Book of Abstracts: Albany 2009

category image Albany 2009
Conversation 16
June 16-20 2009
© Adenine Press (2008)

Kinetics of DNA Force-Induced Melting

Force spectroscopy studies probe nucleic acid structures by exerting tension along the molecule. As it is stretched, double-stranded DNA reveals a sudden increase in length at a constant force, a transition referred to as overstretching. Thermodynamic and chemical evidence have demonstrated that overstretching is actually force induced melting, a transition to single-stranded DNA as base pairing and base stacking are disrupted. We present a predictive model of force induced melting in which thermal fluctuations induce local melting and re-annealing of DNA. These fluctuations are stabilized by the application of tension during the overstretching transition, favoring the conversion to single stranded DNA as the applied force is increased, analogous to the thermal melting of DNA. This model quantitatively predicts small changes in the melting force as the pulling rate is varied. We then test our model for force-induced melting by systematically measuring the midpoint of the transition as a function of pulling rate. Our results suggest that DNA force-induced melting occurs cooperatively with a domain size of 100-200 base pairs.

Micah J. McCauley1
Leila Shokri1
Ioulia Rouzina2
Mark C.Williams1

1Department of Physics
Northeastern University
Boston, MA USA
2Dept of Biochemistry
Molecular Biology and Biophysics
University of Minnesota
Minneapolis, MN USA