aktualisiertes pdf - DPG-Tagungen

SYND 2 Sitzung 2
Zeit: Donnerstag 16:30–18:30 Raum: HS 332
Hauptvortrag SYND 2.1 Do 16:30 HS 332
TDDFT/MM Simulations of Photoactive Proteins —
•Ursula Roethlisberger — Institute of Molecular and
Biological Chemistry, EPFL, 1015 Lausanne, Switzerland
We use a hierarchical mixed quantum mechanical/ molecular
mechanical (QM/MM) simulations to study photoreactions
in biological systems. In this approach, the photoactive
component is treated at the level of gradient-corrected timedependent
density functional theory (TDDFT) whereas the
surrounding biomolecule and the solvent is described via an
empirical force field. We will present results related to the
photoisomerization in bovine rhodopsin and photoactive yellow
protein.
Hauptvortrag SYND 2.2 Do 17:00 HS 332
Helix-Coil Dynamics of Short Peptides — •Feng Gai
— Department of Chemistry, University of Pennsylvanian,
PA 19104, USA
Although the helix-coil transition represents the simplest
scenario in protein folding, the details of its mechanism are
not fully understood. Using laser induced temperature jump
infrared method, we have studied the helix-coil transition of
a series of monomeric peptides. Our results indicate that indeed
the dynamics of the helix-coil transition are complex
and depend on many factors, such as the initial and final
temperature, the capping group, sequence, as well as chain
length. Details of these studies will be discussed.
Hauptvortrag SYND 2.3 Do 17:30 HS 332
Single Molecule Mechanics of Proteins — •Matthias
Rief — Lehrstuhl fuer Biophysik E22, Physikdepartment
der TU Muenchen, 85748 Garching
The mechanical properties of cytoskeletal proteins and
molecular motors are important for their function in vivo.
However, this information has become accessible only recently
through the invention of single molecule techniques
like atomic force microscopy (AFM). We have used AFM
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based force spectroscopy to investigate the mechanical response
of the coiled-coil domains of myosin II and the actin
cross-linking protein Ddfilamin. We find that the myosin
coiled-coil is a highly elastic protein structure that undergoes
an unfolding/refolding transition at 25 pN. Unlike all
other proteins investigated so far this transition occurs in
equilibrium. These measurements show that a coiled-cloil is
able to produce forces during folding. Ddfilamin is an actin
crosslinking protein from dictyostelium discoideum. Using
single molecule unfolding experiments we show that one of
the immunoglobulin domains of this protein unfolds at low
forces via a stable intermediate. We have used amino-acid
inserts into the loops of this domain to map the structure of
this intermediate. We show evidence that the intermediate is
also populated during folding of this domain which increases
the refolding rates drastically. Low unfolding forces together
with fast refolding kinetics suggest an in-vivo role for this
domain as a reversibly extensible element under mechanical
strain.
Hauptvortrag SYND 2.4 Do 18:00 HS 332
Molecular dynamics simulation of single molecule
force probe experiments — •Helmut Grubmüller
— Theoretical and Computational Biophysics Department,
Max-Planck-Institute for Biophysical Chemistry, Am Fassberg
11, 37077 G¨ttingen, GERMANY
Computer simulations of the atomistic dynamics induced
by force probe experiments like atomic force microscopy or
optical tweezers can provide a microscopic picture of these
processes. Typically, however, the experimental and simulation
time scales differ by orders of magnitude. Therefore, in
order to enable comparison with measured forces, computed
forces have to be rescaled to the much slower experimental
time scale. To this aim, we present a non-equilibrium statistical
mechanis approach and apply it to force probe simulation
on biomolecules.