Toward molecular programming with DNA

Biological organisms are beautiful examples of programming. The program and data are stored in biological molecules such as DNA, RNA, and proteins; the algorithms are carried out by molecular and biochemical processes; and the end result is the creation and function of an organism. If we understood how to program molecular systems, what could we create? Lifelike technologies whose basic operations are chemical reactions? The fields of chemistry, physics, biology, and computer science are converging as we begin to synthesize molecules, molecular machines, and molecular systems of ever increasing complexity, leading to subdisciplines such as DNA nanotechnology, DNA computing, and synthetic biology. Having demonstrated simple devices and systems -- self-assembled structures, molecular motors, chemical logic gates -- researchers are now turning to the question of how to create large-scale integrated systems. To do so, we must learn how to manage complexity: how to efficiently specify the structure and behavior of intricate molecular systems, how to compile such specifications down to the design of molecules to be synthesized in the lab, and how to ensure that such systems function robustly. These issues will be illustrated for chemical logic circuits based on cascades of DNA hybridization reactions.