Lecture hall Air/Fire, SciLifeLab, Tomtebodavägen 23 A, Solna at 15:00

Speaker: Sunney Xie, Professor at Harvard University, UK

Title: Label free imaging

Host: Mats Nilsson

Sunney Xie is a pioneer of single molecule enzymology and single cell genomics. Here are some extracts from his homepage: http://bernstein.harvard.edu/

There are many reasons to use the single-molecule approach in biology. First, single-molecule experiments generate movies of motions and biochemical reactions of macromolecular machineries, which are particularly helpful in elucidating their mechanisms. In establishing single molecule enzymology, we developed in vitro assays to probe enzyme activities and conformational dynamics of single molecules, statistical analyses for their stochastic kinetics, and theoretical models for fundamental understanding of the observed phenomena. We have carried out studies of DNA protein interactions; for example, the search of a target DNA sequence by a nonspecifically bound protein, allostery through DNA, and transcription bursting of RNA polymerase induced by DNA supercoiling.

Secondly, there are only one or two copies of a particular gene in an individual cell, which result in stochastic gene expression that cannot be synchronized with other cells. Recently, we achieved single-molecule sensitivity for many proteins, with millisecond time resolution and nanometer precision in a living cell. We were able to observe protein being generated one molecule at a time in E. coli cells and to describe and understand transcription and translation processes at a quantitative level. We found that a single-molecule event can be solely responsible for the life-changing decision of a cell.

On another front, since 1999, our group has led in the rapid development of Coherent anti-Stokes Raman Scattering (CARS) microscopy which was recently superseded by our advance of Stimulated Raman Scattering microscopy (SRS). These are label-free imaging techniques based on vibrational spectroscopy, and are capable of video-rate, noninvasive examination of living cells and organisms. Orders of magnitude more sensitive than conventional Raman microscopy, they allow mapping of 3D distributions of small molecules, such as metabolites and drugs, as well as tumor identification in tissues, which open exciting new possibilities for biology and medicine.