With Matthaei, Nirenberg demonstrated that messenger RNA is required for protein synthesis, and that synthetic messenger RNA preparations can be used to decipher various aspects of the genetic code.

Nirenberg first reported the discovery at the Fifth International Congress of Biochemistry, Moscow, 10-16 August 1961. The paper he presented at that meeting, "The dependence of cell-free protein synthesis in E. coli upon naturally occurring or synthetic template RNA," was not published until 1963. It was published in the first volume (pp. 184-189) of the Proceedings of the fifth International Congress of Biochemistry, Moscow, 10-16 August 1961, Oxford: Macmillan Company persuant to a special arrangement with the Pergamon Press, 1963.

In 1968 Nirenberg shared the Nobel Prize in Physiology or Medicine with H. G. Khorana and R. W. Holley "for their interpretation of the genetic code and its function in protein synthesis."

(Thanks to Juan Weiss for the reference to Nirenberg's paper first announcing the discovery, Moscow, 1961.)