Not everything that Pauling wrote in that famous series of papers from 1951 was correct. A careful scrutiny of his entire oeuvre for that year reveals several weaknesses. In particular, the gamma-helix eventually had to be abandoned. These minor shortcomings, however, don’t take away anything from Pauling’s groundbreaking achievement: the alpha-helix and its prominent role in the structure of proteins. Pauling’s contributions to our understanding of the nature of life were substantial. He was one of the first scientists to see that in spite of its inherent complexity, biology is, at its core, molecular science augmented by the theory of evolution. Already back in 1948, he wrote perceptively: “To understand all these great biological phenomena we need to understand atoms, and the molecules that they form by bonding together; and we must not be satisfied with an understanding of simple molecules . . . We must also learn about the structure of the giant molecules in living organisms.”

Pauling’s influence on the general theory and methodology of molecular biology was equally impressive. First, in his seminal 1939 book The Nature of the Chemical Bond and the Structure of Molecules and Crystals: An Introduction to Modern Structural Chemistry, he remarked prophetically on the importance of the hydrogen bond for biomolecules: “I believe that as the methods of structural chemistry are further applied to physiological problems it will be found that the significance of the hydrogen bond for physiology is greater than that of any other single structural feature.” Indeed, the structure of many organic molecules, ranging from proteins to nucleic acids, confirmed this prediction fully.

Second, Pauling pioneered model building and turned it into a predictive art form based on strict rules of structural chemistry. Even the space-filling colored models developed at Caltech became a hot item in the arena of macromolecular research. These models, produced for labs by the Caltech workshop, fetched as much as $1,220 in 1956 for a set that contained about six hundred atom models.

Pauling’s practice of using the X-ray diffraction patterns not as the starting point but as the ultimate arbiter among sophisticated, educated guesses also proved to be enormously effective—Watson and Crick were about to apply the same approach to the structure of DNA.

There was another remarkable observation concerning genetics that Pauling made in a lecture in 1948, but apparently even he did not realize at the time its full implications. In the first part of that lecture, Pauling reminded his audience: