Tales from the Prep Room: Laser Diffraction

In the second of his Tales from the Prep Room, Ri Demo Technician Andrew Marmery uses wire and a laser pen to recreate the famous cross-shaped diffraction patterns observed by Rosalind Franklin in 1952.

The biophysicist captured "Photograph 51" of DNA whilst working at Kings College London. The photo -- which revealed the structure of DNA -- was later used by James D. Watson and Francis Crick as the basis for their famous model of the double helix.

By shining a laser through different configurations of wire, Andy is able to change the resulting diffraction pattern. Theoretically, he could then work backwards from each pattern to deduce the original position of each wire.

It is this idea that forms the basis of X-ray crystallography, using x-rays instead of laser light, and atoms instead of wires. X-ray crystallography allowed Rosalind Franklin to determine the 3D structure of DNA by analysing the X-ray diffraction patterns of crystals made up of the molecule.

The Ri is on Twitter:   / ri_science  
and Facebook:   / royalinstitution  
and Tumblr:   / ri-science  
Our editorial policy: http://www.rigb.org/home/editorial-po...
Subscribe for the latest science videos: http://bit.ly/RiNewsletter