The Gene: An Intimate History - Siddhartha Mukherjee Page 0,70

it could not accommodate any significant number of water molecules. In their rush to build a model, they had even forgotten Franklin’s first discovery: the remarkable “wetness” of DNA.

The viewing had turned into an inquisition. As Franklin picked the model apart, molecule by molecule, it was as if she were extracting bones from their bodies. Crick looked progressively deflated. “His mood,” Watson recalled, “was no longer that of a confident master lecturing hapless colonial children.” By now, Franklin was frankly exasperated at the “adolescent blather.” The boys and their toys had turned out to be a monumental waste of her time. She caught the 3:40 train home.

In Pasadena, meanwhile, Linus Pauling was also trying to solve the structure of DNA. Pauling’s “assault on DNA,” Watson knew, would be nothing short of formidable. He would come at it with a bang, deploying his deep understanding of chemistry, mathematics, and crystallography—but more important, his instinctual grasp of model building. Watson and Crick feared that they would wake up one morning, open the pages of an august scientific journal, and find the solved structure of DNA staring back at them. Pauling’s name—not theirs—would be attached to the article.

In the first weeks of January 1953, that nightmare seemed to come true: Pauling and Robert Corey wrote a paper proposing a structure of DNA and sent a preliminary copy to Cambridge. It was a bombshell casually lobbed across the Atlantic. For a moment, it seemed to Watson that “all was lost.” He rifled through paper like a madman until he had found the crucial figure. But as he stared at the proposed structure, Watson knew instantly “that something was not right.” By coincidence, Pauling and Corey had also suggested a triple helix, with the bases A, C, G, and T pointed outside. The phosphate backbone twisted inside, like the central shaft of a spiral staircase, with its treads facing out. But Pauling’s proposal did not have any magnesium to “glue” the phosphates together. Instead, he proposed that the structure would be held together by much weaker bonds. This magician’s sleight of hand did not go unnoticed. Watson knew immediately that the structure would not work: it was energetically unstable. One colleague of Pauling’s would later write, “If that were the structure of DNA, it would explode.” Pauling had not produced a bang; he had created a molecular Big Bang.

“The blooper,” as Watson described it, “was too unbelievable to keep secret for more than a few minutes.” He dashed over to a chemist friend in the neighboring lab to show him Pauling’s structure. The chemist concurred, “The giant [Pauling] had forgotten elementary college chemistry.” Watson told Crick, and both took off for the Eagle, their favorite pub, where they celebrated Pauling’s failure with shots of schadenfreude-infused whiskey.

Late in January 1953, James Watson went to London to visit Wilkins. He stopped to see Franklin in her office. She was working at her bench, with dozens of photographs strewn around her, and a book full of notes and equations on her desk. They spoke stiffly, arguing about Pauling’s paper. At one point, exasperated by Watson, Franklin moved quickly across the lab. Fearing “that in her hot anger, she might strike [him],” Watson retreated through the front door.

Wilkins, at least, was more welcoming. As the two commiserated about Franklin’s radioactive temper, Wilkins opened up to Watson to a degree he never before had. What happened next is a twisted braid of mixed signals, distrust, miscommunication, and conjecture. Wilkins told Watson that Rosalind Franklin had taken a series of new photographs of the fully wet form of DNA over the summer—pictures so staggeringly crisp that the essential skeleton of the structure virtually jumped out of them.

On May 2, 1952, a Friday evening, she had exposed a DNA fiber to X-rays overnight. The picture was technically perfect—although the camera had cocked a little off center. “V.Good. Wet Photo,” she had written in her red notebook. At half past six the next evening—she worked on Saturday nights, of course, while the rest of the staff went to the pub—she set up the camera again. On Tuesday afternoon, she exposed the photograph. It was even crisper than the previous one. It was the most perfect image that she had ever seen. She had labeled it “Photograph 51.”

Wilkins walked over to the next room, pulled the crucial photograph out of a drawer, and showed it to Watson. Franklin was still in her office, smoldering with irritation. She had no knowledge that Wilkins had just