Plenarvorträge - DPG-Tagungen

Arbeitskreis Biologische Physik Freitag
und gemessen werden, die als Modellverbindungen für den Einsatz dieser
Sonde in den ” Life Sciences“ dienen werden. Im Vergleich zu anderen
TDPAC-Isotopen verfügt diese Sonde über eine sehr lange Lebensdauer
des Zwischenzustandes (tN = 382 ns) und damit über eine exzellente Frequenzauflösung,
die sie für Dynamik-Studien prädestinieren. Die 204m Pb-
Aktiviät wurde auch mit einem 204 Bi/ 204m Pb-Generator hergestellt. Mit
dieser Sonde sind zum ersten Mal TDPAC-Experimente mit einem Isomer
im ” Heimlabor“ möglich. Die Ergebnisse der 204m Pb-TDPAC-Messungen
am ISOLDE/CERN und an der Uni Leipzig werden vorgestellt.
AKB 50.27 Fr 10:30 B
A model for pathfinding and targeting in mixed populations
of axons — •Peter Borowski and Martin Zapotocky — Max-
Planck-Institut für Physik komplexer Systeme; Nöthnitzer Str. 38; 01187
Dresden
We present a model for the development of a neural map involving
multiple axon species. The model is motivated by the neural connectivity
scheme of the olfactory system, where axons start in a spatially disordered
configuration in the sensory epithelium, yet converge to specific
points on the olfactory bulb depending on which type of odorant receptor
they express. An important ingredient of our model is the presence
of axon-axon interactions which lead to preferential bundling of axons of
the same species. We classify the connectivity patterns that develop in
such a system in the presence and absence of spatially graded guidance
cues, and discuss the robustness of the corresponding neural maps.
AKB 50.28 Fr 10:30 B
Minkowski Functionals of high-dimensional data sets: application
to protein analysis — •Boris Breidenbach 1,2 , Hubert
Mantz 1 , and Klaus Mecke 1,2 — 1 MPI für Metallforschung, Heisenbergstr.3,
70569 Stuttgart — 2 Universität Stuttgart, Institut für theoretische
und angewandte Physik, Pfaffenwaldring 57, 70569 Stuttgart
The Minkowski functionals are a well established tool for the analysis
of various types of spatial experimental data such as tomographic images
of porous materials and atomic force measurements of thin polymer
films where they have proven their ability to extract physically relevant
information. Here, we present the first application of integral geometry in
spaces with more than three dimensions: data is taken from microarray
experiments of gene expression profiles in cells. Each protein is assigned
a point in the high-dimensional concentration space. The functionals can
be calculated exactly and efficiently for such decorated point distributions.
The method is fast and statistically robust. We illustrate it by
analyzing the gene-expression timecourse during the development of the
Drosophila life cycle with respect to its clustering behaviour, i.e., its
protein-protein interactions. The results are subsequently compared to
standard techniques in bioinformatics such as hierarchical clustering and
self-organising maps.
AKB 50.29 Fr 10:30 B
Filament depolimerization by motor molecules — •Gernot
Klein 1 , Giovanni Cuniberti 2 , Karsten Kruse 1 , and Frank
Jülicher 1 — 1 Max-Planck-Institut fuer Physik komplexer Systeme,
Dresden — 2 Universitaet Regensburg, Regensburg
Motor proteins are specialized molecules which bind to filaments of the
cytoskeleton and are able to generate forces. An unusual protein, closely
related to kinesin motors is MCAK, which binds to microtubule ends and
depolymerizes them (1),(2).
We study the process of MCAK binding to microtubules and subsequent
depolymerization using stochastic models.Computer simulations
of a one-dimensional hopping model are compared to the mean-field theory
of the adopted discrete model.Our theory can explain how molecules
accumulate at depolymerizing ends.
(1) A.W. Hunter, M.Caplow, D.L. Coy, W.O. Hancock, S. Diez,
L.Wordeman, J. Howard; Mol. Cell, Vol 11, 445-457, 2003.
(2) R. Ohi, M.L. Coughlin, W.S. Lane, T. Mitchison; Dev. Cell, Vol.5,
309-321, 2003.
AKB 50.30 Fr 10:30 B
In-situ investigation of wood pyrolysis with synchrotron radiation
— •Gerald Andreas Zickler 1 , Cordt Zollfrank 2 , Manfred
Burghammer 3 , and Oskar Paris 1 — 1 Max Planck Institute
of Colloids and Interfaces, Dept. Biomaterials, Am Mühlenberg 1, D-
14476 Potsdam, Germany — 2 Friedrich Alexander University Erlangen-
Nuremberg, Dept. Materials Science - Glass and Ceramics, Martensstr.
5, D-91058 Erlangen, Germany — 3 European Synchrotron Radiation Facility
(ESRF), 6 Rue Jules Horowitz, F-38043 Grenoble, France
Advanced cellular ceramics from biologically derived pre-forms have
gained considerable interest over the last years. Aim of biomimetic materials
synthesis is the transformation of biological tissue into anorganic
structures for the production of biomorphous ceramics and composite
materials with advanced properties. The present study is focusing on
structural aspects of non oxidising pyrolysis of native spruce wood, with
the aim to transform the hierarchical structure of wood into oriented Biocarbon.
Microfocus synchrotron radiation is used in combination with a
custom made furnace to study wood pyrolysis in situ. Scanning the specimens
provides further information on the micrometre scale. Detailed
time resolved diffraction data from single wood slices give deeper insight
into the kinetics of cellulose degradation, nano pore formation and development
of turbostratic carbon at different pyrolysis temperatures. The
results are presented and discussed with respect to existing structural
models of cellulose degradation from literature.
AKB 50.31 Fr 10:30 B
Modelling of Rhodopsin Chromophore — •Minoru Sugihara 1 ,
Ana-Nicoleta Bondar 2 , Peter Entel 1 , Volker Buss 3 , and Marcus
Elstner 4 — 1 Institute of Physics, University of Duisburg-Essen —
2 IWR, University of Heidelberg — 3 Institute of Chemistry, University of
Duisburg-Essen — 4 Institute of Physics, University of Paderborn
Bovine retinal photoreceptor rhodopsin is the only one visual pigment
whose three-dimensional atomic coordinates are available now [1,2]. It
is composed of the 40-kDa apoprotein opsin (348 amino acids) and its
chromophore. The chromophore of rhodopsin is 11-it cis-retinal which
is covalently attached to Lys296 via a Schiff base. The Schiff base nitrogen
atom is protonated and there is a salt-bridge between the protonated
Schiff base and its counterion, Glu113. Illumination of light of ∼
500nm leads to photoisomerization from 11-cis retinal to all-trans within
200fs, which is the primary event in visual system and is the only lightdependent
step. This is followed by a conformational change in the protein
and after a series of intermediates, the pigment reaches the signaling
state, the so-called meta-II. In the present work we focus on the modelling
of the chromophore in the dark state (rhodopsin state) and the
first intermediate state (batho state) based on the crystal structure of
rhodopsin state [2]. We use the recently developed quantum mechanical
/ molecular mechanical (QM/MM) method [3]. [1] K. Palczewski, et al.
Science 2000, 289, 739. [2] T. Okada, et al. Proc. Natl. Acad. Sci, U.S.A.
2002, 99, 5982. [3] Q. Cui, et al. J. Phys. Chem. B 2001, 20, 569.
AKB 50.32 Fr 10:30 B
Unbinding Transitions of Filament Bundles — •Jan Kierfeld,
Torsten Kühne, and Reinhard Lipowsky — MPI für Kolloid- und
Grenzflächenforschung, 14424 Potsdam
Filament bundles are an important structural element of the cytoskeleton.
We study the unbinding transition bundles of semiflexible filaments
such as F-actin. The interaction between the filaments is mediated by
crosslinking stickers. It is shown that the formation of a filament bundle
requires a threshold concentration of stickers. We find that the corresponding
unbinding transition of the filament bundle happens in a single,
discontinuous transition.
AKB 50.33 Fr 10:30 B
Application of micron and nano scale metal island patterns as
coordinative system for quantifying intracellular diffusion —
•Tamas Haraszti and Joachim P. Spatz — University of Heidelberg,
INF 253, 69120 Heidelberg
Quantitative determination of intracellular diffusion in adhering cells
allows access to evaluate dynamics important in cell functions. On very
small length scales we face the problem that the absolute localisation of
a diffusive probe such as fluorescent molecules or quantum dots in cells
relative to the adhering substrate might fail. In our studies we correlate
cellular diffusion to an absolute coordinative system made of micro and
nano scale metal islands. Either e-beam or micellar diblock copolymer
lithography applied to form the desired patterns. The patterns are iden-