2007 – X. Sunney Xie

Holding Single Molecules up to the Light: From in vitro to in vivo Studies

At the single molecule level, a chemical reaction occurs stochastically. We study ever-fluctuating single enzyme molecules and reconcile their enzymatic kinetics with the classic Michaelis-Menten equation. In addition, we have developed new methods to probe spontaneous as well as functionally important conformational dynamics in an intact protein. In a living cell, gene expression is by definition a single molecule problem because of one or two copies of DNA and low copy numbers of most mRNA and some proteins that are involved in the gene expression process. Stochastic events of gene expression give rise to different phenotypes among genetically identical cells or organisms. We have developed methods for probing gene expression at the single molecule level, yielding new and quantitative information regarding the fundamental processes in living cells.