Our research goal is to understand cellular processes at high spatial and temporal resolution by using novel single-molecule manipulation and imaging methods such as Holographic Optical Tweezers, smFRET, and super-resolution PALM/STORM microscopy. We aim for interdisciplinary research that integrates state-of-the-art instrumentation, biological problems of great importance, and quantitative data analysis and modeling in light of statistical physics.

Advanced Optical Microscopy and Trapping

We are endeavoring to innovate optical microscopy. We recently developed one-of-a-kind optical microscope (through optimal integration of wide-field and focused-light microscopies) that is capable of simultaneous epi-fluorescence, total internal reflection fluorescence microscopy, selective plane illumination, and holographic optical tweezers with six lasers. Using this highly versatile microscope, we are carrying out a variety of advanced microscopy assays (e.g. live cell imaging, multi-color single-molecule fluorescence, smFRET, PALM/STORM, FRAP, forcespectroscopy) on biological systems. We continue to further develop the instrument to achieve multi-modal single-molecule assays inside living cells.

Single-molecule Localization Microscopy (SMLM)

The resolution of all the conventional optical microscopies is fundamentally limited to about half the wavelenght of light because of diffraction. Single-molecule localization microscopy, also known as PALM and STORM, circumvents this limit by means of stochastic temporal separation of blinking fluorescent molecules one at a time followed by single-molecule localization with Point Spread Function (PSF) fitting. Our lab ratains expertise in this novel microscopy from the past works on bacteria and eukaryotic cell imaging, such as E. coli FliM, B. subtilis SpoIIIE, mitochondrial double membranes, and mitochondrial fission protein Drp1. We are currently applying SMLM to many other systems in collaboration with Rutgers biologists to reveal previously unresolved intracellular structures at super-resolution.

Mitochondrial DNA Packaging and Transcription

Human mitochondria has its own DNA, called mtDNA. Although it encodes just a small number of genes (13 proteins, 2 rRNA, 22 tRNA), they are all critical for oxydative phosphorylation. Mitochondrial transcription involves three primary proteins, TFAM (Mitochondrial Transcription Factor A), POLRMT (Mitochondrial RNA Polymerase), and TFB2M (Mitochondrial Transcription Factor B2). TFAM is particularly interesting because it bends mtDNA at almost 180 degree when binding to mtDNA. Binding of TFAM to two specific sites on mtDNA (called LSP and HSP promoters) initiates recruitment of POLRMT and transcription. Remarkably, TFAM can also bind to mtDNA nonspecifically and the subsequent DNA bending plays the role of tightly packing mtDNA in similar fashion as histone proteins condense nuclear DNA into nucleosomes. However, the nonspecific interaction does not incur transcription. We are trying to understand the molecular details of specific vs nonspecific interactions between TFAM and mtDNA using single-molecule methods. This work is in progress in collaboration with Smita Patel laboratory at Rutgers.

Innate Immune Response

We are interested in the molecular mechanism of innate immune response of human cells. Using various innovative experimental methods, we are trying to understand how cells detect viral RNA in a very specific manner and further relay the signal to a great amplification. We are particularly interested in the two top upstream signaling processes carried out by RIG-I and MAVS proteins. This work is in progress in collaboration with Smita Patel laboratory at Rutgers. 

Plant Cell Wall Synthesis