Pauling's only real competitor in the field of discovering the structure of complex molecules was Sir William Lawrence Bragg, English Nobel laureate and leader of the laboratory in which Watson and Crick toiled. Bragg and Pauling had competed for scientific priority several times since the late 1920s, when they vied to be the first to publish the structures of large inorganic molecules like silicates (Pauling took the prize); and again for the structure of basic protein components (Pauling won again in 1951). Their competition was low-key and polite, but pointed.

Bragg was a quiet man. He had won his Nobel Prize at a very early age for work with his father on x-ray crystallography. He was head of one of Britain's leading laboratories, the Cavendish at Cambridge. He had little to prove. But he, like Pauling, had become fascinated with the molecular structures of large biomolecules, and had a large, well-equipped team working on proteins, including the eminent researchers Max Perutz and John Kendrew (in whose laboratory Watson, Crick and Peter Pauling worked). They had all been galled when Pauling beat them to the alpha helix. Bragg was weary of coming in second.