Meanwhile, Franklin, on her part, was making significant progress. First, she discovered that DNA occurred in two somewhat different configurations. One form, which she labeled “A,” was crystalline. The other, the “B” form, was more extended and contained more water. One of the consequences of the existence of these two conformations was that the X-ray diffraction photos of DNA samples looked confused unless produced from one pure form. Franklin spent the first five months of 1952 generating pure samples of both the A and B forms, managing to pull out single fibers of each form, and designing and reconfiguring her X-ray camera to take high-resolution pictures. As we shall see shortly, one of the photographs she had produced of the “wetter” B form, which was tagged photograph 51 (see figure 14), was about to become key for understanding the structure of DNA. Unfortunately, because Franklin decided to use a particular method of analysis, she and Gosling concentrated first on the more detailed X-ray pictures of the A form, neglecting the simpler but truly revealing X-ray pattern in photograph 51 for almost nine months!

Figure 14

In all of her research endeavors, Franklin exhibited a striking difference between her way of thinking and Pauling’s. Franklin abhorred “educated guesses” and heuristic methods. Rather, she insisted on relying on the X-ray data to lead her to the right answer. For instance, although she did not object in principle to helical structures, she absolutely refused to assume their existence as a working hypothesis. In contrast, Watson and Crick emulated Pauling’s approach and methods to the fullest, and they were not going to be bogged down in formal methodology. In Crick’s words, “He [Watson] just wanted the answer, and whether he got it by sound methods or flashy ones did not bother him one bit. All he wanted was to get it as quickly as possible.”

Surprisingly, neither Watson and Crick nor Pauling knew at the time that already in 1951, Elwyn Beighton in Astbury’s lab at the University of Leeds had produced excellent X-ray photographs of the B form by stretching the DNA fibers and wetting them. However, since Astbury and Beighton apparently thought that this represented a mixture rather than a pure configuration (because the X-ray pattern was simpler than in the Astbury-Bell pictures), they did not advertise the existence of these photos at all. Unfortunately for Astbury and Beighton, neither of them was familiar with how a helix would appear in X-ray photographs. Just like that, the Leeds lab missed an opportunity to play a significant role in the DNA story.