Rosalind Franklin by Brenda Maddox

Author:Brenda Maddox
Language: eng
Format: epub
Publisher: HarperCollins
Published: 2012-12-29T16:00:00+00:00

Rosalind’s Photograph 51 (shown original size) of the B form of DNA, which told Watson that the molecule was a helix.

Events then moved fast. The following day, 31 January, Bragg unleashed Watson and Crick. He consented to Watson’s request to order metal components from the workshop to begin model-building again. Having Linus’s DNA paper in hand, Bragg was not about to repeat the worst mistake of his life. The thinking at the Cavendish seems to have been, ‘We missed out on the fibrous protein. Now Pauling is going to get the DNA as well.’ When Rosalind started her modelling attempt of the A form, she found her paired-rod structures would not work. She then moved to a figure of eight in which a single chain formed a long column of repeating eights. But by Monday, 2 February, she ruled out the figures of eight as well.

On Wednesday, 4 February Watson started building. His sketch of Rosalind’s Photo 51 confirmed to Crick that they had the right figures with which to put together a B-form model: 20 A diameter, 3.4 A vertical distance between the bases, repeat distance of 34 A and helical slope of about 40 degrees. Although Crick was not entirely convinced that there should not be three chains, Watson was set on two. Once more the disputed phosphates formed the central core, ignoring Rosalind’s argument in 1951 that these water-attracting groups had to be on the outside of the molecule. Crick has supplied the dialogue which shows teamwork in action: ‘‘‘Why not,’’ I said to Jim one evening, ‘‘build models with the phosphates on the outside?’’ ‘‘Because,’’ he said, ‘‘that would be too easy’’ (meaning there were too many models he could build in this way). ‘‘Then why not try it?’’ I said.’

Watson obliged. Crick’s other crucial action on 4 February was to invite Wilkins to come up to Cambridge for lunch on Sunday. Wilkins accepted, saying gullibly, ‘I will tell you all I can remember and scribble down from Rosy.’

On Sunday, 8 February Wilkins arrived to lunch and found that the Cricks had two other guests, eager listeners: Watson and Peter Pauling. When the three men urged him to start model-building to get ahead of Linus, Wilkins vowed to do so as soon as Rosalind was clear of the premises. Watson and Crick wrung from him a grudging consent that they themselves could try again — without telling him that they had already started. Wilkins suddenly realised he was dealing with an awkward situation and left early for London. Had he said too much?

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