Super-Resolution Optical Microscopy
As one of the most powerful imaging techniques for studying cellular processes, fluorescence microscopy allows noninvasive imaging of live samples with molecular specificity. However, the diffraction of light limits the spatial resolution of conventional fluorescence microscopy to several hundred nanometers, leaving many subcellular structures too small to be observed in detail. To overcome this limit, we have developed the Stochastic Optical Reconstruction Microscopy (STORM) technique. Using photoswitchable fluorescent probes and single molecule imaging to determine their 3D positions, it has improved the spatial resolution of optical microscopy by more than an order of magnitude (~20 nm), approaching the size of a protein molecule. We are further pushing the limit of STORM both in its spatial resolution using interferometric optics. We are also developing new experimental approaches and image analysis algorithms to record fast processes in living systems.
Macromolecular Complexes
Modern structural biology methods, such as X-ray crystallography, NMR and cryoEM, have provided us powerful tools to determine biomolecular structures ranging from small proteins to large macromolecular complexes. However, it is still a major challenge to connect these in vitro isolated structures to their native cellular counterparts. Funded by the NIH Director's New Innovator Award, we are developing a new approach based on super-resolution optical microscopy to characterize the architecture of molecular complexes in situ. Especially, we are interested in studying the nuclear pore complex, the centrosome, and the basal body - transition zone - primary cilium structure.
Spatial Regulation of Cell Signaling
Regulation of signal transduction inside a cell not only depends on concentrations and free diffusion. In many cases, clustering, compartmentalization and spatial segregation of signaling molecules also play important roles, which add another layer of versatility in controlling molecular interactions. We are trying to elucidate these mechanisms using single-molecule imaging and super-resolution microscopy, with particular focus on live cell studies. The systems of our interest are G-protein coupled receptor signaling and the signaling molecules involved in neuron development. We are also developing methods to monitor the fast dynamics of lipids and lipid membranes.