Chemists at Harvard University have developed the first technique providing a real-time, molecule-by-molecule “movie” of protein production in live cells. Their direct observation of fluorescently tagged molecules in single cells – providing striking real-time footage of the birth of individual new protein molecules inside – greatly increases scientists’ precision in probing genetic activity.

Using the new assay, described in the journal Science, researchers led by Harvard’s X. Sunney Xie counted, one by one, protein molecules generated in small bursts within cells as multiple ribosomes bound to single copies of mRNA complete the process by which DNA, an organism’s long-term genetic repository, yields its crop of proteins. These random, or stochastic, bursts of protein expression are described in detail in a separate paper Xie and colleagues presented in Nature.