The Marcus group studies the structure and dynamics of macromolecules in biological environments. These include the diffusive motions and internal structural changes of proteins in membranes and in living cells, as well as the conformational fluctuations of macromolecular machines that interact with and manipulate DNA. To elucidate the conformations of macromolecular complexes, and to monitor their time dependent behavior, we develop and apply linear and nonlinear spectroscopic methods that are sensitive to the electronic couplings between fluorescent chromophore labels. Spectroscopic characterization of exciton-coupled dimer probes, which are attached at specific locations on the macromolecules, allows us to observe functionally important macromolecular conformations. For example, by using fluorescent nucleic acid analogues placed at sites near the forks and junctions of primer-template DNA, we study the effects of protein-DNA interactions on local base-stacking conformation. In collaboration with UofO Prof. Peter von Hippel, we are investigating the mechanisms of polymerase and helicase, two protein-DNA complexes central to gene expression. Extension of our techniques to single molecule fluorescence imaging allows us to observe bio-molecular events in real time.

  Protein dynamics, intracellular transport.