Abstract

A cell is the common unit structure shared by all living organisms. But even ‘simple’ prokaryotic cells are extremely complex chemical reactors. In recent years, great progress has been made in determining the diffusion coefficients of proteins in living cells, science is beginning to appreciate the stochastic nature of gene expression, and models for reaction diffusion systems in signaling pathways are emerging. However, we do not understand the basic underlying physical organic chemistry of the cell. We do not know at what point the familiar chemistry in dilute solutions ceases to be a valid description of the chemistry in crowded environments that are present in the cell. The main problem is our lack of access to kinetic and thermodynamic data for intracellular reactions in crowded ‘life-like’ environments. In my talk, I will explain how we are constructing a robust experimental platform to elucidate the precise influence that the particular physiochemical conditions commonly found in living systems have on model complex biochemical reactions. Monodisperse water-in-oil microdroplets, ~10-100μm in diameter and surrounded by a monolayer of surfactant, allow for reactions to be studied systematically on a minute scale under idealized conditions. Droplets can be formed, fused, split, sorted and interrogated using fluorescence spectroscopy at kHz rates in microfluidic devices. In these droplets we introduce the machinery required for transcription and translation and then we study the cell-free expression of proteins as a function of physical parameters. These studies allow us to use picoliter droplets as artificial cells.