Microfluidic 'Buttons'

Biophysicist Stephen R. Quake and graduate student Sebastian J. Maerkl of Stanford University report a high-throughput microfluidic device that can monitor transient and low-affinity molecular interactions (Science 2007, 315, 233). Such interactions can be difficult to track, because the binding molecules can be easily washed off in other devices. The new device features "buttons," shown in blue, that mechanically trap the bound molecules on a surface to enable their detection; the red and green channels control valves for samples and reagents. As each button closes, it forces water out of the chamber along with any unbound molecules. The device provides an "instantaneous snapshot of the binding equilibrium, which we can then interrogate at our leisure," Quake says. With the device, Quake and Maerkl measured DNA binding energy landscapes of four transcription factors each bound to one of 464 target DNA sequences. They used the data to test assumptions about transcription factor binding and to predict the genes that the transcription factors might regulate.