PIER Photon Science Colloquium: Watching the dance of water in the hydration shell of ions and biomolecules in the THz frequency range

by Martina Havenith

Friday, November 18, 2011 from to (Europe/Berlin)
at Seminarrom ( 28c Flash Halle )
In recent years a new frequency window has been opened: The THz range. In pioneering studies it could be shown that THz absorption spectroscopy is a new tool to study the solvation dynamics of biomolecules [1]. THz spectroscopy probes sensitively the fast (sub-ps) collective network dynamics of bulk water. Accompanying ab initio MD simulation unravel the underlying molecular motions: In contrast to the mid infrared regime - where the absorption peaks can be assigned to intramolecular motions - in the frequency regime below 1000 cm-1 intermolecular motions with concerted particle motions dictate the spectrum [2]. Precise measurements of absorption coefficients of solvated solutes in the THz regime allow now a precise view on changes in hydration dynamics of solutes during biological function [3-5]. 

[1]  S. Ebbinghaus, S.J. Kim, M. Heyden, X. Yu, U. Heugen, M. Gruebele, D.M. Leitner, M. Havenith, "An extended dynamical solvation shell around proteins," Proc. Natl. Acad. Sci. USA, 104, 20749 (2007).
[2] M. Heyden, J. Sun, S. Funkner, G. Mathias, H. Forbert, M. Havenith, D. Marx  Dissecting the THz spectrum of liquid water from first principles via correlations in time and space. Proc. Natl. Acad. Sci. USA, 107, 12068 (2010).
[3] D.A. Schmidt, Ö. Birer, S. Funkner, B. Born, R. Gnanasekaran, G. Schwaab, D.M. Leitner, M. Havenith, Rattling in the cage: Ions as probes of sub-ps water network dynamics, J. Am. Chem. Soc., 131(51), 18512-18517 (2009).  
[4] S.J. Kim, B. Born, M. Havenith, M. Gruebele, Real-time detection of protein-water dynamics upon protein folding by terahertz absorption, Angewandte Chemie Intl. Edition 47 (34), 6486-6489 (2008).
[5]  M. Grossmann, B. Niehues, M. Heyden, D. Tworowski, G.B. Fields, I. Sagi, M. Havenith (2010), Correlated structural kinetics and retarded solvent dynamics at the metalloprotease active site, Nature Structural & Molecular Biology, published online 18.9.2011; doi:1038/nsbm.2120