Transmission electron microscope image shows direct visualisation of DNA bundle

The DNA was suspended in water droplets which were then evaporated to leave behind the strands suspended between pillars

Italian scientists have developed a technique to improve the contrast of electron microscopy images of DNA fibres. By suspending the bundles of six or more double-stranded DNA helices between microscale pillars above a silicon surface, they eliminated a lot of the background noise that would normally be a problem when looking at DNA on surfaces.

To suspend the fibres, the team exploited the tendency for surfaces covered with regular arrays of microscopic features to be superhydrophobic. This allowed them to place droplets of aqueous DNA fibre solutions on the surface. As the droplets dry, the DNA is left behind, stretched between the pillars.

The silicon substrate below has a hole in between each pair of pillars, through which the transmission electron microscope electron beam could be focused to image the fibres. This allowed the team to clearly visualise and measure the periodic features of the DNA strands that make up the fibres, particularly on the strand closest to the edge of the bundle. 

References

F Gentile et al, Nano Lett., 2012, DOI: 10.1021/nl3039162