Single Enzyme Activity Detected with a Nanoelectronic Sensor

Abstract

Today's single molecule studies rely almost exclusively on force-based detection and/or optical detection. A third, fundamentally new, detection technology utilizes the electrostatic signals generated by single molecules. using the protease thermolysin we show that enzymatic activity can be detected with single turnover resolution using a carbon nanotube field-effect transistor sensor. A single thermolysin molecule is site-specificially immobilized to the carbon nanotube via a cysteine residue. In the presence of a thermolysin substrate the sensor shows discrete switching between two conductivity levels. The switching signal depends on the substrate concentration, and does not occur in the absence of substrate. We envision that this approach can be generalized to a large number of enzymes, allowing for single enzyme studies of many enzyme-substrate systems.View Large Image | View Hi-Res Image | Download PowerPoint Slide