Direct image of DNA’s double helix captured for the first time

02 Dec 2012 , 16:00

London:Scientists have for the first timecaptured a direct image of the double helix of DNA, thestructure that encodes the genetic instructions of all livingorganisms.

Enzo di Fabrizio and colleagues from the University ofGenoa, Italy, developed a technique to capture the doublehelix of DNA using a scanning electron microscope, the DailyMailreported.

Deoxyribonucleic acid (DNA) molecules encode the geneticinstructions used in the development and functioning of allknown living organisms and many viruses.

Representational image. Agencies.

Along with RNA and proteins, DNA is one of the three major macromolecules that are essential for all known forms of life. Previously the DNA helix could only be detected using atechnique known as X-ray crystallography, which involvesscattering X rays off atoms in crystallised arrays of DNA.

Capturing the reflected rays on photo film forms the nowiconic fuzzy X inside a fuzzy O pattern that James Watson andFrancis Crick used to discover the double-helix structure.

However, because of the indirect nature of the image,Watson and Crick were only able to infer the existence of thedouble helix using complex mathematics to interpret the image.

Now Professor Di Fabrizio and his team from Genoa’sNanostructures Department have used a scanning electronmicroscope to creat the first direct image of the DNA doublehelix.

The researchers developed a process to capture DNA threadsout of a dilute solution and dry them and stretch them outacross water-repellent nanoscopic silicon pillars, NewScientist reported.

By drilling tiny holes through the base of their bed ofnano-nails and shining electrons through them, they were ableto create high resolution images of a strand of DNA.

The remarkable image clearly shows the DNA double helix,as predicted by Watson and Crick nearly 60 years ago.With refinement, the Genoa team hope that their newtechnique will allow researchers to watch single molecules of DNA as they interact with other biomolecules.

Since the electron energies are high enough to snap DNAmolecules, at the moment the method only works with ‘cords’ ofDNA made of six molecules wrapped around a seventh acting as acore.

Di Fabrizio and his team now hope to use more sensitivedetectors that can detect lower-energy electrons. This shouldallow them to see individual double helices and even unwoundsingle strands of DNA.

“With improved sample preparation and better imagingresolution, we could directly observe DNA at the level ofsingle bases,” New Scientist quoted him as saying.The research was published in the journal Nanoletters.


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