Dynamic AFM force spectroscopy of DNA using FM mode with constant excitation

Experimental Biophysics and Applied Nanoscience, Department of Physics, Bielefeld University Universitaetsstrasse 25, D-33615 Bielefeld, Germany

Received: 16 December 2016
Accepted: 13 March 2017

Abstract

We report single-molecule force spectroscopy experiments on double-stranded DNA using a dynamically oscillating AFM cantilever driven in a frequency modulation mode with a constant excitation (CE) amplitude. While the DNA molecule is stretched, we measured the shift of the cantilever amplitude and the resonance frequency and estimated both the conservative forces and the dissipated energy. Typical elastic features of the calculated force distance curves are in nice agreement with data known from quasi-static stretching experiments. Analysis of the data indicates that the melting dynamics of the DNA base pairs depends on the amount of already melted base pairs and the base pair recombination rate. Furthermore, we observe a reduction of the molecular elasticity modulus, which is most likely caused by the cantilever dynamics leading to a destabilization of stacking and hydrogen bond interactions.