GENOMICS/ATOMIC FORCE MICROSCOPY: AFM collaboration produces first in-situ view of DNA's double helix

Bart Hoogenboom uses atomic force microscopy (AFM) to achieve spatial resolution on large biomolecules in situ of about 1 nm. Hoogenboom is a lecturer with University College London (UCL) and the London Centre for Nanotechnology (LCN; a joint venture between UCL and Imperial College London), where he is also lead scientist for LCN's AFM facilities. In addition to simple visualization, AFM enables his laboratory's study of how biomolecules work.

AFM enables viewing of plasmid DNA at different magnifications; green dashed lines and arrows indicate the strands of the double helix. At bottom, the measured profile along the DNA is compared to an atomistic model of the DNA double helix. (Imagery courtesy of Carl Leung and Bart Hoogenboom, University College London)

Hoogenboom's team collaborates with JPK Instruments AG (Berlin, Germany) to push instrumentation to new limits of resolution and imaging. The collaboration recently resulted in a publication in Nano Letters that reported the first visualization of the DNA double helix in water. "The resolution obtained on DNA is an example of our success in extending the capabilities of AFM instrumentation," said Hoogenboom. "Most present-day microscopes do not achieve any higher resolution on DNA than was achieved with the first AFM experiments in the early 1990s."

Hoogenboom notes that, "The distinctive feature of our recent results is the visualization of both DNA strands in the double helix. It is not new that DNA is a double helix, but about 60 years after its discovery, it is the first time that we see it in the molecule's natural, aqueous environment."