In 1950, Khorana and Kenner were reunited in Todd's laboratory at the University of Cambridge. Though neither could possibly have realized it at the time, Cambridge was emerging as one of the centers of a new molecular revolution that, during the next decade, would permanently transform biology. Central to the emergence of molecular biology was the “Unit for Research on the Molecular Structure of Biological Systems” set up in 1947 by the (British) Medical Research Council (MRC), originally to further the research of Max Perutz and John Kendrew in using X-ray diffraction to study proteins with the goal of determining their three-dimensional structure at an atomic resolution, a feat that had never before been attempted. Perutz and Kendrew would solve the myoglobin molecule in 1957 and hemoglobin in 1959 to be rewarded with the Nobel Prize in Chemistry in 1962.

In the early 1950s, the MRC Unit rapidly expanded its interest into other areas, including the structure of DNA, which would be elucidated on site by Francis H. C. Crick and James D. Watson using data from the work of Maurice Wilkins and Rosalind Franklin. The result was the double helix model for DNA, which was first published in 1953, and soon became the most visible icon of the new molecular biology. The unit was initially located in the Physics Department at the Cavendish Laboratory, indicating a perceived centrality of physics for the new molecular characterization of biological problems. Crick, who later became one of Khorana's closer intellectual interlocutors, had a background in physics and joined the MRC Unit in 1949, shortly before Khorana returned to Cambridge, but there is no evidence that they became acquainted at the time. The organic chemists lived in another world. Nevertheless, it was fortuitous that Todd also worked on nucleic acids. Khorana thus was kept aware of recent developments in that field.

Meanwhile, closer to Khorana's everyday work, in the Department of Biochemistry, Frederick Sanger was taking the chemical analysis of proteins to a new level of precision. That proteins consisted of polypeptides or amino acid residue chains (which means the same thing) had been known since the turn of the twentieth century.