X. Sunney Xie

Among the first to conduct single-molecule imaging, spectroscopy, and dynamical studies at room temperature, I have been working on single-molecule biophysical chemistry, in particular, single-molecule enzymology. My group was able to monitor enzymatic turnovers of a single enzyme in real time, and probe conformational fluctuation of a single protein at a broad range of time scales through photoinduced electron transfer. We found that an enzyme is a dynamic entity that does not exhibit constant enzymatic activity; yet the Michaelis-Menten equation still holds at the singlemolecule level. In recent years, I have been studying gene expression and regulation in living bacterial cells at the single-molecule level. My lab was able to monitor protein production one molecule at a time, which allowed a quantitative description of the Central Dogma. We observed how a transcription factor finds specific sequences on DNA, and showed that a stochastic event of a single transcription factor can solely determine a cell?s phenotype. We also conducted system wide single-cell analyses of transcriptome and proteome with single-molecule sensitivity. My lab has also developed coherent Raman scattering microscopy, which allows highly sensitive label-free 3D imaging of living organisms based on vibrational spectroscopy, providing a useful tool for biology and medicine.