My research is focused on rotary molecular motors, in particular the Bacterial Flagellar Motor, which is a rotary molecular engine powered by the flow of ions across the inner, or cytoplasmic, membrane of a bacterial cell envelope. Each motor drives a protruding helical filament, and the rotating filaments provide the propulsive force for cells to swim. We use a range of optical techniques to try and understand how these living machines work.
Molecular motors are tens of nanometres in size, and we measure their motion using novel forms of light microscopy to follow visible "handles" such as sub-micron gold or polystyrene spheres and single fluorescent molecules. We measure the position of the handles with nanometre and sub-millisecond resolution using fluorescence microscopy, laser dark-field microscopy and laser interferometry. Optical tweezers (3-D laser traps) and other methods are used to push single motors around. We also use single-molecule fluorescence microscopy to detect separate components of the motors and assess how they interact with each other.