Abstract:

A cell is a complex unity of various biomolecules with diverse functions. Understanding molecular mechanisms in cells requires detecting biomolecules with high chemical selectivity and resolution. Chemical imaging using optical modalities allows to visualize molecular compositions in cells with high spatial and temporal resolution. In this talk, I will first review common linear and nonlinear chemical imaging technologies such as fluorescence and coherent Raman scattering microscopy. A recent development in improving the sensitivity of nonlinear optical microscopy using a pulse-picking method will also be introduced. Next, I will discuss the recent development of a real-time precision opto-control (RPOC) technology for precise control of molecular activities in live cells. This new technology enables new capabilities and understanding that cannot be achieved in conventional ways. Applying RPOC, we demonstrate selective conversion of the state of photochromic molecules at desired locations of cells, inducing reactive oxygen species at desired organelles, inhibiting tubulin polymerization at subcellular locations, and quantifying the photosensitization effect of common fluorescent dyes. RPOC also allows us to interrogate how femtosecond lasers with different average and peak power interact with organelles and perturb cell functions.

About the Speaker: 

Dr. Chi Zhang is an Assistant Professor at Purdue University, Department of Chemistry. He received his Ph.D. degree from the University of Michigan, Department of Chemistry with a research emphasis in surface nonlinear optical spectroscopy supervised by Dr. Zhan Chen. He joined Dr. Ji-Xin Cheng’s group at Purdue University in 2014 as a Postdoc Associate working on chemical imaging and coherent Raman microscopy. He also did his Postdoc work with Dr. Stephen Boppart at the University of Illinois for biomedical imaging and spectroscopy before starting his independent research career at Purdue University in 2020. The current research focus of his lab is developing novel optical imaging and opto-control technologies for biological applications. His lab pioneered the RPOC technology for precision optical manipulation of biomolecules in cells. He has published more than 50 peer-reviewed journal articles. His research is supported by the National Institute of Health, the National Science Foundation, and the Center for Bioanalytical Metrology.