The chemistry of living things is complicated. To synthesize a protein molecule from the information encoded in a single gene, a cell must first transcribe the DNA into messenger RNA; then the mRNA is translated to produce a protein. Additional reactions inactivate the mRNA and degrade the protein when the cell no longer needs them. Altogether, more than 100 enzymes and other molecules are involved in the reactions, and the translation process is especially complicated, as shown schematically in the figure. Gaining quantitative insight into the reaction dynamics by observing living cells is a daunting challenge: Many of the molecules are also involved in other reactions going on at the same time, so it is difficult to look at the synthesis of one protein in isolation.
But now Vincent Noireaux (University of Minnesota), Roy Bar-Ziv (Weizmann Institute of Science in Israel), and their colleagues have carried out a complete...