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CeNS Colloquium

Kleiner Physik-Hörsaal, Fakultät für Physik
Date: 15.01.2016, Time: 15:30h

It is water what matters: THz absorption spectroscopy as a new tool to study solvation dynamics

Prof. Dr. Martina Havenith, Ruhr-Universität Bochum

Within the last decade the THz experimental gap between the IR and MW has been closed. Since then Terahertz (THz) absorption spectroscopy has turned out to be a new powerful tool to study (bio)molecular hydrationTHz spectroscopy of solvated salts provides a detailed molecular picture of ion hydration, a key issue in chemistry. The THz range captures the socalled "rattling modes" i.e. the correlated motion of cations and anions with its hydration cage as well as allow to catch the onset of ion pairing and allows to distinguish between contact ion pairs, solvent separated ion pairs and solvent shared ion pairs. These experimental advances had to go hand in hand with the development of theoretical concepts which are able to adequately describe these anharmonic collective modes in the THz range. More recently, time resolved THz time domain  spectroscopy allows to record snapshots of the low frequency spectrum of a solvated proteins subsequent to initiating protein folding, thus capturing changes of low frequency spectra of solvated proteins during biological function. This is of major importance since under ambient, physiologically relevant conditions 90% of the modes which contribute to the total entropy of the solvated protein are captured by the low frequency modes of the protein/solvent, i.e. the vibrational density of states (VDOS) between 0 and 10THz (300cm-1). Our most recent results underlie the importance of the collective water-protein modes in the THz frequency range for molecular recognition.

References:
D.A. Schmidt, Ö. Birer, S. Funkner, B. Born, R. Gnanasekaran, G. Schwaab, D.M. Leitner, M. HavenithRattling in the cage: Ions as probes of sub-ps water network dynamics, J. Am. Chem. Soc. 131(51), 18512-18517 (2009).
M. Grossmann, B. Born, M. Heyden, D. Tworowski, G.B. Fields, I. Sagi, M. Havenith, Correlated structural kinetics and retarded solvent dynamics at the metalloprotease active site, Nature Structural & Molecular Biology 18, 1102-1108 (2011).
K. Meister, S. Ebbinghaus, Y. Xu, J.G. Duman, A. DeVries, M. Gruebele, D.M. Leitner, M. Havenith, Long-range protein-water dynamics in hyperactive insect antifreeze proteins, Proc. Natl. Acad. Sci. U.S.A 110(5) 1617-1622 (2013).
V. Conti Nibali, M. Havenith, New insights into the role of water in biological function: Studying solvated biomolecules using terahertz absorption spectroscopy in conjunction with molecular dynamics simulations, J. Am. Chem. Soc. 136(37), 12800-12807 (2014).