Letter from Melvin Cohn, Washington University School of Medicine to Michael Heidelberger

Biochemists and other biomedical researchers depend on one another for substances and preparations they used in their experiments. Cohn here mentioned that he was supplying Heidelberger with B-galactosidase, an enzyme that helps bacteria ferment sugar and that played a key role in bacterial genetics research in the 1950s. Cohn also mentioned the use of radioactive tags to identify individual proteins in solutions.