Studies of the Dynamics of Intracellular Species using Phase-Selective Fluorescence Fluctuation Spectroscopy

The intracellular environment is a dynamic, multi-component fluid, with relaxations spanning a broad range of length and time scales. Understanding the molecular basis of intracellular transport is a challenging problem due to the myriad chemical species and physical processes at play. In my talk, I will discuss some of our recent experiments to study the motions of mitochondria in living yeast cells, and how these motions depend on the properties of the intracellular matrix. In these experiments, we apply a novel phase-selective optical approach to measure the coordinate fluctuations of a population of fluorescent particles. I will next discuss how we are extending these experiments towards mechanistic studies of the biochemical machinery of gene regulation. When a macromolecular complex is labeled with two or more closely spaced fluorescent chomophores, the resulting resonant dipole-dipole coupling is sensitive to the local macromolecular conformation. Phase-selective measurements of excited state energy transfer within the complex allow us to map out competing kinetic pathways of protein conformational transitions.