Pauling's work on magnetic properties of hemoglobin piqued his interest in other proteins; however, he already was intrigued by them. While visiting the Rockefeller Institute in spring of 1935, Pauling convinced Simon Flexner, the institute's president and a member of the Rockefeller Foundation's board of trustees, to send Alfred E. Mirsky to Caltech for one year. Pauling and Mirsky analyzed the structure of native, denatured and coagulated proteins during the same time that Pauling and Coryell researched the magnetic properties and structure of hemoglobin and its derivatives.

Mirsky already knew a good deal about the denaturation of proteins and had worked on the denaturation of hemoglobin, thus Pauling hoped that Mirsky would help him improve his own understanding of proteins. Together they investigated what happens structurally when a native protein (in the natural state) is denatured (altered). They found that the tertiary structure of native proteins (i.e. the structure produced when a sequence of amino acids folds and binds to itself) depends upon hydrogen bonds, which allow the folded protein to hold its shape. During denaturation the hydrogen bonds break down and the protein loses its tertiary structure. Hemoglobin was one of the substances they analyzed.

Pauling's knowledge about hemoglobin and its derivatives would greatly aid his ability to understand the sickling process undergone by sickle cell hemoglobin. However, this was not for another seven years, in which time he learned more about chemical reactions within the human body, especially about immunology.