Nanotube Detects Enzyme Motion

Enzymes and nanotubes may seem unlikely partners in a molecular two-step. But by tethering lysozyme to the carbon nanotube in a field-effect transistor (FET), scientists are now able to electronically monitor the enzyme’s movements (Science, DOI: 10.1126/science.1214824). This approach gives researchers a new way to follow enzyme movement over relatively long periods of time—something that can be difficult to do with fluorescence techniques because of signal bleaching. Gregory A. Weiss, Philip G. Collins, and colleagues from the University of California, Irvine, modified T4 lysozyme, an enzyme that hydrolyzes polysaccharides in bacterial cell walls, by covalently attaching a pyrene anchor to one of its cysteine residues. The pyrene then associates via π–π interactions to the single-walled carbon nanotube that makes up the FET’s conductive channel. As the enzyme moves, the FET detects changes in electrostatic potentials. In this manner, the researchers were able to tune into two different hinge-bending motions in the enzyme: one that comes from the hydrolysis of the polysaccharide and one that arises from nonproductive binding events.