Physics Colloquium
Friday, November 14th, 2003 4 P.M.

Joachim D. Mueller

Physics Department
University of Minnesota

Observing Protein Assembly in Living Cells with
Two-photon Fluorescence Fluctuation Spectroscopy

Each cell in our body contains a huge number of proteins. These proteins fulfill specific biological functions that collectively keep the cellular machinery alive. Proteins do not act in isolation, but associate into transient or stable protein complexes. The interactions responsible for protein assembly establish complex protein-protein networks that regulate all cellular pathways. These networks, although crucial for cellular function, are not well studied, because we lack experimental techniques that quantify protein interactions under physiological conditions. Two-photon fluorescence fluctuation spectroscopy is a promising new approach for probing protein-protein interactions directly in the living cell. I will demonstrate that molecular brightness of proteins tagged with green fluorescent protein (GFP) is a useful and robust parameter for in vivo studies. By performing brightness analysis we succeeded in probing the self-association of nuclear receptors in the nucleus of cells. Our results demonstrate the potential of fluorescence fluctuation spectroscopy to develop into a quantitative tool for characterizing protein-protein interactions in intact cells.

Refreshments 3:30 P.M. Room E200 Math/Science Center