February 24th, 2015
The general structure of DNA is well-known to most people: almost everyone will get a flash of two intertwined strings with coloured lines in opposing colour sets in between them. Already in 1953, James Watson and Francis Crick discovered that the core structure of our genetic material, DNA, has this double-helix structure. It was one of the major discoveries in science of the 20th century and has led to innumerable applications in all areas of science.
But although we know about the structure for decades already, until now, no one was ever able to capture the double helix structure in an image directly. That is, until last week. Almost 60 years after its discovery, Francesco Gentile et al. (2012) managed to take a picture of two strands of DNA, in which the double helix is clearly visible.To get this done, the researchers used transmission electron microscopy (TEM).This is a very sensitive technique that allows imaging with intrinsic spatial resolution at atomic scale. But the resulting images can be impaired easily. The contrast of the atomic particles in the molecule with their substrate background can be too small, or the molecule can get damaged by the high energy electron beam that is used. Gentile et al. covered these problems by using a new kind of sample preparation method. By placing the strands of DNA on a super hydrophobic surface, they made use of the self-aggregation process of the DNA to make it actually stable enough for photographing it.
The result is not just a nice picture, confirming something we already knew. On the contrary: now that researchers found a method to take such a close look on the DNA structure, it becomes possible to look directly at interference of it with other molecules. So this is research that opens new doors for knowledge on DNA: new large steps can now again be made.
Gentile, F. Moretti, M. et al. (2012). ‘Direct imaging of DNA fibers: the visage of double helix.’ Nano Letters. DOI: 10.1021/nl3039162
Photo by Enzo di Fabrizio (2012)