This paper investigated the part played by collaborative practices in chaneling the work of prominent biochemists into the development of molecular biology. The RNA collaborative network that emerged in the 1960s in France encompassed a continuum of activities that linked laboratories to policy-making centers. New institutional frameworks such as the DGRST committees were instrumental in establishing new patterns of funding, and in offering arenas for multidisciplinary debates and boundary assessment. It should be stressed however, that although this collaborative network was (...) based on centralized initiatives aimed at developing molecular biology as a new biological specialty, it operated above all as a nexus of practices. The main argument of this paper is that the central allocation of funds and resources, exemplified by the DGRST operation, actually enhanced the creation of a self-conscious community of biochemists turned molecular biologists by virtue of an increased circulation of tools, skills, and results that took place within the RNA network and a few analogous systems of exchange.Having hands on “things” viewed as identical for all practical purposes was a potent factor in changing the experimental systems and their meanings. Limited but shared means of doing helped to reduce uncertainties, change representations, and turn contingent decisions into meaningful choices. The collaborative enterprises then resulted in personal contacts and the transfer of skills and materials, which gradually incorporated the biochemical tools into systems producing facts relevant to molecular biology as defined by its early practitioners. In that sense, networking was a regulatory process that stabilized new research objects and acculturated French biochemists.The mere existence of such a collaborative network also changed the scale of the disciplining process. Collaborations may have been started for contingent motives, but multiple exchanges resulted in the emergence of a new collective, and amplified small displacements. Collaborations, however, worked both ways, and the RNA network may be viewed as an efficient “trading-post.” An unexpected outcome of the development of a conversion zone is the fact that, by the late 1960s, the former biochemists dominated the “new” world of molecular biology — both in terms of research habits, since interests in structural studies dominated the field, and in terms of institutional initiatives such as the creation of laboratories and institutes for molecular biology.As an example of the cognitive displacements achieved by the network, I have focused here on the stabilization of “messenger RNA” as a new biological entity. This process illustrates the role of “boundary objects” and other mediating innovations in the development of disciplinary structures. Students of science trained in the symbolic interactionism tradition have proposed that “boundary objects” enhance the multiple interactions between heterogeneous social worlds: they are robust enough to enhance unity, but plastic enough to be manipulated in different social and cultural contexts.81 Within the emerging network, messenger RNA was a weakly structured “genetic information carrier” in common use, but it could, at the same time, be a strongly structured “macromolecular structure” adapted to practical and local uses. Consequently, messenger RNA favored the association of groups of heterogeneous scientists with backgrounds and interests in medical biochemistry, genetics, physical chemistry, organic chemistry, and so forth. This contrast between general and local uses was also instrumental in integrating the manipulation of things and the negotiation of aims. In contrast to transfer RNAs, which in the French context remained objects for chemical (and mainly structural) studies, messenger RNA became a key component of the new culture of “genetic information”. Messenger RNA was a loose theoretical entity described as a “genetic information carrier” in the policy-making documents, while operational but tacit and more conflicting definitions prevailed at the bench. In other words, messenger RNA was not only a classical “boundary object” but also a “flag object,” which tightened the collaborative network by mediating between the DGRST offices and the laboratories. (shrink)