It would be an understatement to say that molecular machines have been under a tremendous amount of pressure lately. Proponents of nanotechnology have left them variously responsible for curing the world’s diseases, providing mankind with limitless food, water, energy and information, and even self-assembling so we don’t have to make them ourselves. And that’s only a partial list. Under the weight of such towering expectations, can we really blame them if they give up and turn the planet into grey goo?
Perhaps in an effort to save us from such an apocalyptic scenario, some nanoscientists have set more leisurely intermediate goals for molecular machines, like getting them to play games. A group of researchers from Columbia University recently developed a two-player strategy game between a human player and DNA-based molecular computer called “tit-for-tat”. The rules are simple: players take turns marking squares of a 2×2 grid, communicating their choice through biomolecular inputs on the human side and optical responses on the DNA side. The DNA player “wins” as long as it does not try to mark a quadrant that has been previously marked.
Unlike previously reported DNA games, such as molecular tic-tac-toe, tit-for-tat is built from reconfigurable DNA molecules, allowing the computer to be trained to move according to a particular strategy. Not only does this flexibility make for tougher competition, but it also brings us one step closer to building general purpose DNA computers.
But even games can be stressful for a molecular machine. How about just taking a walk? In March, the same Columbia University group, along with collaborators from Arizona State University and Caltech, demonstrated the controlled movement of a DNA walker. Their spider-like molecular walker heeds simple commands like start, turn, and stop embedded into a two dimensional “track”, which is also made from DNA.
Propelled by thermal energy, the walker avoids retracing its steps by chemically modifying portions of the track it has visited before. This is an improvement on earlier designs which achieved only random and/or one dimensional directed motion. While walking on a track may not appear to be much fun, future plans involve getting multiple robots to interact on a single track as well as embedding “clues” in the track that give the walker some freedom to choose its next step.
Still not convinced we are doing enough to keep our future servants (or should I say masters?) happy and productive? Maybe not, but it’s a start. After all, from a molecular standpoint, playing games sure beats the thankless task of solving all the world’s problems at once. For a more detailed look at how researchers are able to construct molecular machines out of DNA, check out Paul Rothemund’s TED talks on the topic of DNA origami.
Pei R, Matamoros E, Liu M, Stefanovic D, & Stojanovic MN (2010). Training a molecular automaton to play a game. Nature nanotechnology, 5 (11), 773-7 PMID: 20972436
Lund K, Manzo AJ, Dabby N, Michelotti N, Johnson-Buck A, Nangreave J, Taylor S, Pei R, Stojanovic MN, Walter NG, Winfree E, & Yan H (2010). Molecular robots guided by prescriptive landscapes. Nature, 465 (7295), 206-10 PMID: 20463735