Plenarvorträge - DPG-Tagungen
Plenarvorträge - DPG-Tagungen
Plenarvorträge - DPG-Tagungen
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Arbeitskreis Biologische Physik Freitag<br />
AKB 50.95 Fr 10:30 B<br />
Global pattern formation from local cell-to-cell communication<br />
— •Thimo Rohlf and Stefan Bornholdt — IZBI, University of<br />
Leipzig, Kreuzstr. 7b, 04103 Leipzig, Germany<br />
A central observation in developmental biology is the self-organization<br />
of spatial gene expression patterns on scales much larger than cell size. In<br />
existing models, this is often explained by morphogen gradients, which<br />
are established by Turing instability of activator-inhibitor systems [1].<br />
However, pattern formation in these models depends on parameter tuning<br />
of, e.g., diffusion constants. The role of gene regulation in development<br />
is neglected. Here we sketch a new process of global pattern formation<br />
from local information transfer without the need for parameter tuning.<br />
We study a three-state cellular automaton which reproduces two basic<br />
experimental observations at the polyp Hydra: de novo pattern regeneration<br />
and regulation of expression domain size proportional to system<br />
size.<br />
The model shows remarkable robustness with respect to noise and cell<br />
movement. Similar mechanisms could in principle occur in biological organisms<br />
where direct contact induction is present.<br />
[1] Gierer, A. and Meinhardt, H., Kybernetik 12, 30 (1972)<br />
AKB 50.96 Fr 10:30 B<br />
A biological solar energy generator — •Dieter F. Ihrig 1 , H.<br />
Michael Heise 2 , Alexander Moor 2 , Manuel Gemuend 1 , Darius<br />
Wilczek 1 , Ruediger Kuckuk 2 , and Martin Poschmann 1 —<br />
1 FH Suedwestfalen Iserlohn, Germany — 2 Institut fuer Spektrochemie<br />
und angewandte Spektrometrie, Dortmund, Germany<br />
Biomass production by micro algae is by a factor of 10 more efficient<br />
then plants. This gives the chance to create an economic process of solar<br />
energy harvesting. In view of the very low dry mass content of algal<br />
suspensions the most promising way of conversion to a high exoergic and<br />
transportable form of energy is the anearobic production of biogas.<br />
We are actually developing such processes especially micro algal reactors,<br />
a method to separate micro algal cells, a method to treat the micro<br />
algal biomass and a two stage anaerobic process. First results of these<br />
project sections are shown. The developed anaerobic process is very efficient<br />
but also very unstable. To get a better process management it is<br />
necessary to understand the influences between the parameters of process<br />
engineering and biochemical parameters like the concentration of<br />
carboxylic acids. Goal of this part of the project is the development of<br />
an inline sensor. The project was funded by the German Federal Ministry<br />
for Education and Research (BMBF).<br />
AKB 50.97 Fr 10:30 B<br />
FCS used to study translational mobilities in plasma membranes<br />
of living cells — •Margarita Khazarchyan 1 , Elmar<br />
Thews 1 , Carsten Tietz 1 , Jörg Wrachtrup 1 , Sylvia Willi 2 ,<br />
Anja Krippner-Heidenreich 2 , and Peter Scheurich 2 —<br />
1 3.Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring<br />
57, 70569 Stuttgart — 2 Institut für Zellbiologie und Immunologie,<br />
Universität Stuttgart, Allmandring 31, 70569 Stuttgart<br />
Fluorescence correlation spectroscopy (FCS) is an attractivce method<br />
of measuring molecular concentrations, chemical kinetics and diffusion<br />
processes in living cells. We use one- and two-photon excitation for the<br />
investigation of translational mobility in cytoplasm and in plasma membranes<br />
using different fluorophores for intracellular applications of FCS.<br />
Measurements in living cells and in plasma membranes are feasible with<br />
reasonable signal-to-noise ratios, even with fluorophore concentrations on<br />
a single molecule level in the detection volume.<br />
We present an application of this method to study TNF(Tumor Necrosis<br />
Factor)-R1, TNF-R2 in plasma membranes and TRAF2-protein in<br />
cytoplasm of living cells. Other investigations demonstrated that TNF-R<br />
and TRAF-proteins involved in the cells apoptotic pathway. Apoptosis is<br />
the specific controlled mechanism of cell death which is distinct from uncontrolled<br />
necrotic cell death. Apoptosis requires tight regulation. Lack of<br />
such regulation leads to either too much or too little apoptosis, resulting<br />
in pathological conseqeunces, such as Alzheimer disease or cancer.<br />
Diffusion coefficients of the signal TNF-R and TRAF2-protein were<br />
determined before and after stimulation with TNF ligand.<br />
AKB 50.98 Fr 10:30 B<br />
Stepwise rotation of the epsilon-subunit of EFoF1-ATP synthase<br />
during ATP synthesis and hydrolysis - a single-molecule<br />
FRET approach — •Michael Börsch 1 , Boris Zimmermann 2 ,<br />
Nawid Zarrabi 1 , Manuel Diez 2 , and Peter Gräber 2 —<br />
1 3. Physikalisches Institut, Universität Stuttgart — 2 Institut für<br />
Physikalische Chemie, Universität Freiburg<br />
F-type ATP synthases catalyze the formation of ATP by coupling<br />
two rotary motions of subunits within the enzyme. We attached<br />
tetramethylrhodamine-maleimide at the rotating epsilon-subunit and<br />
Cy5-bismaleimide crosslinking the two b-subunits, and reconstituted the<br />
enzymes fully functional into liposomes. Fluorescence resonance energy<br />
transfer (FRET) was monitored in photon bursts of freely diffusing ATP<br />
synthases with a confocal setup for single-molecule detection. Incubation<br />
with non-hydrolysable AMPPNP resulted in stable intensity ratios<br />
within a burst and three different FRET efficiencies corresponding to<br />
the three possible orientations of the epsilon-subunit.<br />
Upon addition of ATP at mM concentrations, a consecutive order of<br />
three distinguishable FRET efficiencies was observed indicating a stepwise<br />
movement of the epsilon-subunit, comparable to the stepwise rotation<br />
of the gamma-subunit in EFoF1 [1,2]. Under the conditions for ATP<br />
synthesis stepwise rotation of the epsilon-subunit was observed in opposite<br />
direction. Dwell-time analysis revealed heterogeneity of the three<br />
catalytic binding sites.<br />
[1] M. Borsch et al. (2002) FEBS lett. 527, 147-152.<br />
[2] M. Diez et al. (2004) Nat. Struct. Mol. Biol., in press.<br />
AKB 50.99 Fr 10:30 B<br />
DNA translocation through a biological nanopore — •Ulrich F.<br />
Keyser 1 , N. Wennersbusch 1 , D. J. Bonthuis 1 , N. H. Dekker 1 ,<br />
X. S. Ling 2 , and Cees Dekker 1 — 1 Molecular Biophysics, Delft University<br />
of Technology, Lorentzweg , 2628 CJ Delft, The Netherlands1 —<br />
2 Brown University, Providence, USA<br />
We study the translocation of single-stranded DNA (ss-DNA)<br />
molecules through a single biological nanopore, viz., an alpha-Hemolysin<br />
pore from Staphylococcus aureus assembled within a lipid membrane.<br />
The inner diameter of this nanopore is only 1.5 nm and ss-DNA molecules<br />
can be transferred one by one. Applying a bias voltage at high salt concentrations<br />
gives rise to an ionic current through the nanopore. If a ss-DNA<br />
molecule enters the pore the current is partly blocked and the passage<br />
of a molecule is detected. We are investigating different types of ss-DNA<br />
with various lengths and sequences to study the influence on the translocation<br />
speed and current. The experimental results will be compared to<br />
recent theoretical models.<br />
AKB 50.100 Fr 10:30 B<br />
Immobilisation of the Light harvesting complex LH1 of<br />
Rhodospirillum rubrum on nanostructured surfaces — •Britta<br />
Götze, Carsten Tietz, and Jörg Wrachtrup — 3. Physikalisches<br />
Institut, Universität Stuttgart, Germany<br />
Sunlight is the driving force on this planet. To make it useable plants<br />
and bacteria have created a sofisticated system- the photosynthetic apparatus<br />
-.The final product of this system is ATP - the most common<br />
transporter of energy in every living thing.<br />
The first step in this apparatus is to capture sunlight as excitation<br />
energy and transfer it to the reaction center. Here a charge seperation<br />
takes place as a initializing step in photosynthesis.<br />
In this work the light harvesting complex LH1, a pigment protein complex<br />
of the purple bacterium Rhodospirillum rubrum is investigated. The<br />
studies have been performed on nanostructured as well as on modified<br />
surfaces. The aim of this work is to investigate the possibility of long<br />
range 1d energy transfer between light harvesting complexes on nanostructured<br />
surfaces.<br />
The structures are made using electron beam lithography and consist<br />
of gold/titanium on SiO2. A self assembled monolayer is formed on top<br />
of them using different types of mercaptanes.<br />
First step was to figure out what kind of mercaptane offers the best adsorbance<br />
properties for the light harvesting complexes./par Second step<br />
was to proof a specific binding / adsorbance of the proteins on the modified<br />
surface./par Third step will be to get a densly package of proteins<br />
on these structures.