Hodgkin and colleagues, including biochemist Barbara Low, solved the structure of penicillin in 1945, demonstrating, contrary to scientific opinion at the time, that it contains a β-lactam ring. The discovery was originally published by Crowfoot (Hodgkin) and Rogers-Low in 1945 in a classified report (Committee for Protein Synthesis [CPS] report #508). The work was first made public in 1949.

In 1949 Hodgkin and Low published another version of their report in Florey, Chain et al, Antibiotics: A survey, vol. 2, ch. 27, "Structure of the penicillin molecule," pp. 946-951.

Hodgkin used an IBM ‘CPS’ (Card Programmed, electronic Calculator), to perform the extremely complex math/generation/interpretation of the Fourier
synthesis yielding the 3D structure. This use of a programmed electronic punched-card tabulator was a very early use of a programmed device to speed up structure factor computation in x-ray crystallography.

With Charles W. Bunn and Annette Turner-Jones.

(Thanks to Juan Weiss for this reference and its interpretation.)