Tying new knots in synthetic biology.

Recent years have seen the emergence of synthetic biology, which encompasses the engineering of living organisms as well as the implementation of biological behavior in non-living substrates. Many of these engineered systems have harnessed the diverse toolkit of proteins, genes, and cellular processes that nature offers. While these efforts have been fruitful, they have also illustrated the difficulty associated with programming highly complex functions by tapping into cellular processes. Another set of efforts has focused on building circuits, performing computation, and constructing nanoscale machines using nucleic acids. Zhang et al., 2007, Science 318, 1121-1125 and Yin et al., 2008, Nature 451, 318-322 recently demonstrated flexible approaches for the modular construction of such biochemical devices exclusively using DNA. These approaches have exciting implications both for engineering living cells and for mimicking life-like behavior at the nanoscale.