Date/Time
Date(s) - 22/10/2010
2:00 pm - 3:00 pm

Title: Beyond Steady-State Protein Dynamics

Speaker: Dr. Thomas HauÃ?, Helmholtz-Zentrum Berlin

Institute: Helmholtz-Zentrum Berlin für Materialien und Energie

Location: ABB 315

Description:

It is well accepted that proper functioning of a protein requires a well-defined three-dimensional structure. But beside its structure the protein needs a certain degree of internal flexibility to allow larger conformational rearrangements in the millisecond time scale. This flexibility is governed by stochastic positional fluctuations and quasi-diffusive atomic motions on a picoseconds time scale summarised as protein dynamics. Protein dynamics has been extensively studied with the methods of inelastic and quasi-elastic neutron scattering; but so far, the correlation of internal protein dynamics with the function of proteins was investigated only indirectly in steady-state experiments by variation of external parameters like temperature or hydration.
To study protein dynamics beyond steady-state experiments we have developed a novel laser-pump:neutron-probe experiment which allows us to monitor temporal changes in protein dynamics during a working cycle of a protein. The method comprises of an in-situ optical activation of a protein and a time-dependent sampling of the dymamic response using quasi-elastic neutron scattering. With the membrane protein bacteriorhodopsin, a light driven proton pump, we can demonstrate for the first time temporary alterations in the protein dynamics after triggering the working cycle. This observation is a direct proof for the functional significance of protein structural flexibility, in connection with the large-scale conformational changes in the protein structure occurring during the operation of a â??molecular machineâ?. Functionally important modulations of protein dynamics as observed here are surely of relevance for most of the proteins that exhibit conformational changes in the time course of its functional operation. The impact of improved instrumentation on studies of time-resolved protein dynamics on the new spallation sources in the USA, in Japan, and in Europe will be discussed.

References
1. J. Pieper, A. Buchsteiner, N. A. Dencher, R. E. Lechner, T. HauÃ?, Transient Protein Softening during the Working Cycle of a Molecular Machine, Phys Rev Lett, 100, 228103 (2008)
2. J. Pieper, A. Buchsteiner, N. A. Dencher, R. E. Lechner, T. HauÃ?, Light-induced Modulation of Protein Dynamics During the Photocycle of Bacteriorhodopsin, Photochem Photobiol, 85, 590-597 (2009)