When Pauling's much anticipated DNA manuscript arrived via Peter in early February 1953, both researchers were surprised to see something that looked like their own abortive three-chain effort, only more tightly put together. A few minutes' reading showed that there was no room at the core for the positive ions needed to hold together the negatively charged phosphates.

Crick and Watson were dumbfounded. Pauling's structure depended on hydrogen bonds between the phosphate groups, but how could there be a hydrogen there when the phosphates in DNA lost their hydrogens at normal pH? "Without the hydrogen atoms, the chains would immediately fly apart," Watson said. They had already been through this with their own model, but they checked it again, and there it was in black and white in a respected text: The phosphates had to be ionized. The text they consulted was Pauling's General Chemistry. "If a student had made a similar mistake, he would be thought unfit to benefit from Caltech's chemistry faculty," Watson later wrote.

He and Crick immediately went off to confirm their criticism with Cambridge's chemists. Before the day was out, Pauling's mistake was the talk of the college. With obvious satisfaction, Crick wrote Pauling, "We were very struck by the ingenuity of the structure....The only doubt I have is that I do not see what holds it together." Pauling's apparent misstep pleased Bragg so much that he officially agreed to let Crick and Watson go back full-time to DNA. There was a window of opportunity here, and he wanted the Cavendish to take advantage before Pauling had time to regroup.