Franklin and her work

Philips micro-camera and Photo 51Rosalind Franklin took up a Turner and Newall Fellowship at King's College London in January 1951. Her work as an experienced experimental x-ray researcher was well known to Randall.

Franklin took over from Wilkins and worked with Gosling on using the new equipment to improve the quality of images on nucleic acids.

Franklin improved the stability and controllability of the humidity of the specimen environment to ensure the reproducibility of images and improve the scope for greater precision in analysis.

Meanwhile, Wilkins assisted by Herbert Wilson sustained detailed work on water absorbency of DNA filaments and also made rough tests on to see if DNA had the same structure in all kinds of living things.

At the centre of all the patterns he found a diffuse 'X' shape. A R Stokes pointed out that this would be given by helical DNA with an angle of ascent like a spiral staircase of 40%.

'A'-form of DNAWork by Franklin and Gosling during 1951 and 1952 demonstrated that the sodium salt of DNA prepared by Signer could exist in two distinct structures, A and B depending on the water content. This pointed to the key significance of phosphate groups for the structure.

Franklin and Gosling's images showed that using Signer's extracted DNA, A and B forms could be reliably demonstrated at 75% and 92% humidity respectively.

Philips micro-cameraThe clear X in the centre of the B form gave scientists further confirmation that the DNA structure was helical. The dark patches on the outside were understood to point to the importance of atoms of the phosphate groups.

Their work involved supreme precision and required tilting the camera to systematically refine definitions and disclose layering.

Additional work involved Gosling measuring angles between dark spots on x-ray images displayed in overhead projections onto white sheets serving as makeshift screens, while Franklin issued instructions from the back of the room.

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