Upon separation of the protein from the nucleic acid component of tobacco mosaic virus by phenol, using a fast and gentle procedure, the nucleic acid is infective in assays on tobacco leaves. A series of qualitative and quantitative control experiments demonstrates that the biological activity cannot depend on residual proteins in the preparation, but is a property of isolated nucleic acid which is thus the genetic material of the virus.

Between the 1930s and 1950s, life science had evolved into a sophisticated and expensive scientific enterprise. Under the influence of the Rockefeller Foundation's program of molecular biology, vital processes, especially the properties of proteins, were increasingly probed through systematic applications of tools from the physical sciences. This trend altered the nature of biological knowledge, the organization of research, and patterns of funding for the life sciences, transforming laboratory research into 'big science' — a team activity centered around massive apparatus. The (...) development of the Tiselius apparatus during the 1930s and 1940s serves as an example par excellence of these nascent intellectual and institutional trends. The paper shows that the Tiselius apparatus and the research it spawned represented one of the early collaborative projectes organized around a major laboratory technology. From its inception, design, construction, and early uses the new electrophoresis technology was a joint-effort between Svedberg's group at the University of Uppsala, the Rockefeller Institute, and a few other elite institutions. These collaborations reflected access to resources, and a commitment to a scientific agenda which stressed the physico-chemical approach to biological phenomena. The collaborations were based on the 'protein paradigm' — the view that proteins were the primary determinants of biological specificity. By examining the intellectual programs and the institutional network around the Tiselius apparatus, this paper also underscores the fruitfulness of studying the history of laboratory technology of the life sciences. (shrink)