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J. Heinrich Matthaei coauthored experiments with Marshall Warren Nirenberg using cell-free protein synthesis and synthetic polyribonucleotides to investigate the genetic code.

Supplying a simple RNA template and measuring amino-acid incorporation connects nucleotide sequence with protein composition. The experiment separates the informational role of the template from the catalytic machinery already present in the extract.^[ref]

Identity and discipline: njc.rockefeller.edu/pdf3/NirenbergMatthaeiPNAS1961.pdf

Marshall Warren Nirenberg coauthored cell-free experiments connecting synthetic RNA with amino-acid incorporation into proteins. With J. Heinrich Matthaei, he used the response to defined polyribonucleotides to investigate the genetic code.

A defined template changes one component of a complex extract while the other biochemical machinery remains available. This makes the observed incorporation informative about the template's coding role.^[ref]

Identity and discipline: findingaids.nlm.nih.gov/repositories/ammp/resources/nirenberg566

Additional identity: www.history.nih.gov/illustrated-histories/nih-biographies-plus/nirenberg-marshall-w-1927-2010

In 1961, Marshall Warren Nirenberg and J. Heinrich Matthaei ground washed Escherichia coli and used centrifugation to prepare a cell-free extract. Reactions at $35^{\circ }\mathrm{C}$ combined ribosomes, soluble components, ATP regeneration and phenylalanine carrying a ${}^{14}\mathrm{C}$ isotope label, with or without polyuridylic acid, an RNA containing only U. After incubation, trichloroacetic acid precipitation, washing and counting radioactive decay detected label in insoluble material. Added polyuridylic acid strongly increased incorporation; removing ribosomes or ATP regeneration suppressed it. Product characterization supported a phenylalanine polypeptide.^[ref]

The inference connects an imposed RNA template to a specific amino acid product. Yet repeated U alone cannot distinguish one-, two- or three-letter coding units: every possible group still contains only U. Neither triplet length nor the complete genetic code follows.^[ref]

By Marshall Warren Nirenberg and J. Heinrich Matthaei; the printed byline is Marshall W. Nirenberg and J. Heinrich Matthaei. Proceedings of the National Academy of Sciences of the United States of America, volume 47, issue 10, pp. 1588–1602 (1961). The 3 August 1961 communication date is distinct from publication on 15 October 1961, reported in the worker-inspected PubMed record.

DOI: doi.org/10.1073/pnas.47.10.1588

Primary article scan hosted by Rockefeller University: njc.rockefeller.edu/pdf3/NirenbergMatthaeiPNAS1961.pdf

Bibliographic record: pubmed.ncbi.nlm.nih.gov/14479932/

The National Institutes of Health is the authors’ printed affiliation; Rockefeller University is the scan host.

Cited passages: printed pp. 1589–1590, Methods and Materials; p. 1592, Table 1 assay footnote; p. 1595, Table 6; pp. 1596–1599, Figure 6 and Tables 7–9; pp. 1600–1601, product characterization, Discussion and Note added in proof.