Search this Site

Print this page
RSS

Michigan State University

Protein and Hydration-Shell Dynamics in Chromoproteins: Exploring the Energy Landscape at Equilibrium and Far from Equilibrium with Time-Resolved Fluorescence and Photon-Echo Spectroscopy

Warren Beck

Tuesday April 03, 2012

1:30pm PHYS 242

Coffee and doughnuts served at 1:15pm in the same room

http://www2.chemistry.msu.edu/faculty/beck/

The dynamic reorganizational or solvation response of the protein and solvent medium that surrounds the active chlorophylls and carotenoids in photosynthetic reaction-center and light-harvesting complexes plays an important role in the quantum efficiency of the overall conversion of solar photons into stored chemical potential. The motions that are triggered and sensed by the pi-pi* transitions of intrinsic chromophores can be probed in chromoproteins using stimulated photon-echo spectroscopy on the femtosecond timescale and time-resolved fluorescence spectroscopy on the picosecond–nanosecond timescale. In ZnII-substituted cytochrome c, which we use as a model for a single chlorophyll-containing protein, correlated protein motions on the 100-ps timescale account for a major fraction of the reorganization energy. How these motions report the formation of intermediates on the protein-folding reaction coordinate and how they are correlated with the ultraslow motion of hydrogen-bonded water structures in the hydration layer will be discussed.