Force spectroscopy on DNA by FM-AFM

TL;DR

This paper demonstrates the use of non-contact AFM in ultra-high vacuum to quantitatively measure forces and energies of DNA molecules adsorbed on mica, providing high-resolution imaging and chemical contrast.

Contribution

It introduces a method for quantitative force spectroscopy of DNA using NC-AFM in UHV, revealing chemical contrast along DNA molecules.

Findings

Force and energy measurements of tip-DNA interactions were obtained.

High-resolution images confirmed contrast differences between substrate and DNA.

Force curves along DNA showed distinct classes indicating chemical contrast.

Abstract

We present imaging and force spectroscopy measurements of DNA molecules adsorbed on functionalized mica. By means of Non-Contact mode AFM (NC-AFM) in Ultra High Vacuum (UHV), the frequency shift (\Delta f) versus separation (z) curves were measured providing a quantitative measurement of both force and energy of the tip-DNA interaction. Similarly, topographic images of the adsorbed DNA molecules in constant frequency shift mode were collected. The high resolution force measurements confirm the imaging contrast difference between the substrate and DNA. The force curves measured along the DNA molecule can be divided into two classes showing marked differences in the minimum of the interaction force and energy, indicating that NC-AFM could deliver chemical contrast along the DNA molecule.