One may still wonder what it was that convinced Watson and Crick that the DNA structure was at all solvable rather than being an irregular mess. Conceivably, it was a talk Maurice Wilkins had given at a meeting in Naples, Italy, in the spring of 1951—a meeting that Watson attended. Wilkins succeeded in pulling extremely thin fibers of the sodium salt of DNA, and in producing X-ray photographs that were significantly superior to the ones by Astbury and Bell. The pictures showed a crystalline form of DNA, which indicated to Watson that the structure was regular. These were the same pictures that Pauling had requested from Wilkins.

Upon receiving Pauling’s letter, Wilkins, who was fully aware of Pauling’s abilities when it came to molecular structure, did not quite know what to do about the request. Eventually, he replied politely that his pictures were not ready to share until he had the opportunity to carry out some additional investigations. Pauling did not give up, and he decided to try his luck with Randall, only to be refused again on the grounds that “it would not be fair to them [Wilkins and his collaborators], or to the efforts of our laboratory as a whole, to hand these over to you.” So by the end of 1951, Pauling was still unable to see any X-ray diffraction images of reasonable quality.

Meanwhile, Watson and Crick were becoming increasingly obsessed with the desire to beat Pauling at deciphering the structure of DNA. The Austrian-American biochemist Erwin Chargaff, who met Watson and Crick in May 1952, gave a humorous description of the dynamic duo: “One, thirty-five years old; the looks of a fading racing tout, something out of Hogarth . . . The other, quite undeveloped at twenty-three, a grin, more sly than sheepish; saying little, nothing of consequence.” Even funnier was Chargaff’s depiction of the burning ambition of the two scientists: “So far as I could make out, they wanted, unencumbered by any knowledge of the chemistry involved, to fit DNA into a helix. The main reason seemed to be Pauling’s alpha-helix model of a protein.” Indeed, even though Pauling was unaware of it, Watson (in particular) and Crick (to some extent) saw themselves as participating in a race against him.

One should not get the impression that Pauling was the first to introduce helical models, but he certainly had a major role in making such models the choice for molecules of biological significance. By introducing a non-integer number of amino acids per turn in his alpha-helix model, Pauling expanded further the horizons of traditional structural crystallographers. Consequently, research into the interpretation of the X-ray diffraction patterns from helical structures received a huge boost, establishing the tools for the eventual deciphering of DNA. As Crick described the general thinking around that time: “You would be eccentric, looking back, if you didn’t think DNA was helical.”

Toward the end of 1951, events started to progress rapidly. On November 21, 1951, Watson made a trip to London to hear a colloquium by Rosalind Franklin. Even though he did not learn much new from that lecture, barely a week passed before he and Crick produced their first model for the structure of DNA. The model consisted of three helical strands and had a sugar-phosphate backbone on the inside, with the bases pointing outward. The main motivation for this particular design was simple: Since the bases were of different sizes and shapes (two were single ringed and two were double ringed; see figure 13), Watson and Crick didn’t see how the crystalline DNA could produce a highly regular pattern unless the bases were relatively uninvolved in the central architecture.