aktualisiertes pdf - DPG-Tagungen
aktualisiertes pdf - DPG-Tagungen
aktualisiertes pdf - DPG-Tagungen
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Fachsitzungen<br />
– Hauptvorträge –<br />
SYND 1 Sitzung 1<br />
Zeit: Donnerstag 14:00–16:00 Raum: HS 332<br />
Hauptvortrag SYND 1.1 Do 14:00 HS 332<br />
Theory and Design of Multidimensional IR Pulse Experiments<br />
— •Christoph Scheurer — Lehrstuhl für<br />
Theoretische Chemie, TU München, 85748 Garching<br />
Femtosecond visible and infrared (IR) multiple-pulse techniques<br />
based on the control and manipulation of multiple<br />
quantum coherences provide new tools to probe the structure<br />
and dynamics of complex molecular assemblies. The control<br />
over time delays in a pulse sequence yields multidimensional<br />
spectra with increased resolution and information content<br />
as compared to 1-D experiments. Structural and dynamical<br />
information is contained in the position, shape, and temporal<br />
evolution of cross and diagonal peaks that are due to<br />
anharmonicities in the underlying system Hamiltonian and<br />
its coupling to the environment. Ultrafast laser pulses thus<br />
allow to obtain picosecond snapshot pictures of the molecular<br />
structure along dynamic trajectories. These experiments<br />
are theoretically best described in the framework of the density<br />
matrix formalism. In the weak-field limit a multiplepulse<br />
experiment can be conveniently represented by a set<br />
of double-sided Feynman diagrams. The design of multidimensional<br />
vibrational spectroscopies can draw upon analogy<br />
with liquid or solid state nuclear magnetic resonance (NMR)<br />
spectroscopy which are well established for studying structure<br />
and dynamics of complex systems on slower timescales.<br />
Hauptvortrag SYND 1.2 Do 14:30 HS 332<br />
Investigating Ultrafast Peptide Dynamics by 2D-IR<br />
Spectroscopy — •Peter Hamm, Jens Bredenbeck,<br />
and Jan Helbing — Universität Zürich, Physikalisch<br />
Chemeisches Institut, Winterthurerstr. 190, 8075 Zürich,<br />
Schweiz<br />
Recent work has shown that two-dimensional infrared (2D-<br />
IR) spectroscopy might be a valuable experimental complement<br />
to existing tools to study conformation of small peptides<br />
in the solution phase. 2D-IR spectroscopy allows one<br />
to measure the couplings between certain vibrational modes,<br />
which are related to the relative orientation of the peptide<br />
units, and hence allows one to extract structural information.<br />
Great progress has been achieved recently in resolving the<br />
structure, structural distribution and structural fluctuations<br />
of a small peptide, trialanine. The most promising potential<br />
of 2D-IR spectroscopy is its intrinsic high time resolution (1<br />
ps), which freezes in all motions of a peptide backbone. On<br />
the one hand, this allows one to resolve rapidly exchanging<br />
conformations of an equilibrium ensemble of peptides. On the<br />
other hand, one can monitor how a non-equilibrium ensem-<br />
195<br />
ble evolves in time with 1 ps time resolution. The emerging<br />
possibilities of 2D-IR spectroscopy will be discussed.<br />
Hauptvortrag SYND 1.3 Do 15:00 HS 332<br />
Simulation of conformational dynamics and energy<br />
transfer in peptides — •Yuguang Mu, Phuong<br />
Nguyen, and Gerhard Stock — Institut für Physikalische<br />
und Theoretische Chemie,J. W. Goethe-Universität,<br />
Marie-Curie-Str. 11, D-60439 Frankfurt<br />
Recent multidimensional vibrational experiments have provided<br />
a wealth of new information on peptides and proteins.<br />
To study the correlations between spectra and peptide<br />
dynamics and to obtain a microscopic understanding<br />
of the phenomena, molecular dynamics (MD) simulations of<br />
various small peptides in aqueous solution have been performed.<br />
From these simulations, time-dependent correlation<br />
functions reflecting vibrational dephasing, energy transfer<br />
and energy relaxation are computed and compared to experiment.<br />
Furthermore, nonequilibrium MD simulations of<br />
laser-induced peptide dynamics are presented and analyzed.<br />
The validity and accuracy of nowadays available MD models<br />
and methods are discussed.<br />
Hauptvortrag SYND 1.4 Do 15:30 HS 332<br />
Ultrafast Conformational Dynamics in Cyclic Peptides<br />
— •Josef Wachtveitl — Goethe-Universität<br />
Frankfurt, Institut für Physikalische und Theoretische<br />
Chemie, Marie-Curie-Straße 11, 60439 Frankfurt am Main<br />
Structural changes of peptides containing a modified<br />
azobenzene dye(AMPB) are studied with ultrafast spectroscopy.<br />
AMPB peptides represent a new class of molecules<br />
where the photoisomerizable dye azobenzene is linked to the<br />
peptide moiety via a flexible methylene spacer. The ultrafast<br />
reactions in the femtosecond to nanosecond time domain<br />
are investigated for the optical switch AMPB, a linear and<br />
cyclic octapeptide and a bicyclic octapeptide containing an<br />
additional disulfide bridge. These molecules with increasing<br />
conformational constraints, are studied for the cis to trans<br />
and the trans to cis photoreactions. For the cis to trans reaction<br />
the isomerization of the chromophore occurs fast in<br />
the 1 ps range, while it is slower (10 ps range) in the trans<br />
to cis reaction. In all peptides the structural changes of the<br />
chromophore lead to modifications in the peptide structure<br />
in the 10 ps to 1 ns time range. The results indicate that the<br />
chromophore AMPB acts simultaneously as a fast molecular<br />
switch and as a sensor for initial conformational dynamics in<br />
the peptide.