2012 Thesis Prize Award Ceremony - Fondation Nanosciences

Dynamics of controlled actin network’s
architecture
Anne-Cécile REYMANN
PhD of University of Grenoble
iRTSV/PCV
Laureate of the
‘2012 Thesis Prize’
Actin networks are one of those fabulous self-organized
biopolymers that sustain cell architecture while those
perform highly complex mechanical transformations in
order to achieve efficient morphogenesis, cell motility
or any cell shape changes. Perpetual dynamics,
organization, regulation or rapid reconstruction are only
a few of the properties required for these morphological
features which are supported by the actin cytoskeleton.
During my thesis, I have developed different projects in
order to tackle the problem of actin network dynamics
and organization as well as the molecular mechanism
at the origin of force production in biomimetic
reconstituted systems. Stepping aside from the
conventional actin based particles’ motility studies,
one of the major innovations was to generate highly
ordered auto-assembled actin motifs, finely tuned by
the reproducible spatial control of actin nucleation
sites by micropatterning. Moreover the presence of
molecular motors, such as myosin, on these controlled
systems allowed us to reproduce some of the cellular
biomechanical processes of tension and contractility.
A direct visualization of filaments demonstrates
a spectacular myosin-induced actin network
deformation and disassembly that depend on the
original network architecture.
Following an “orientation selection” mechanism such
phenomenon could therefore play an essential role in
the spatial regulation and scalability of expanding and
contracting regions of actin cytoskeleton in cells.
Ioan Mihai POP
PhD of University of Grenoble
Institut Néel
Laureate of the
‘2012 Thesis Prize’
Coherent quantum phase-slips in a
Josephson junction chain
The central result of my thesis is the observation
of quantum phase-slips in Josephson junction
networks. A phase slip is associated with the
passage of a magnetic quasi-particle (a “fluxon”)
through a Josephson junction chain.
We have observed the quantum interference of
phase slips, an effect predicted by Y. Aharonov
and A. Casher in 1984. This is the electromagnetic
dual of the well-known Aharonov-Bohm effect.
We have also demonstrated that a chain of
Josephson junctions, which is a complex
mesoscopic object, can accurately be treated
as a single quantum object, with few degrees of
freedom.
These results open the way for a wide range
of possible uses of quantum phase-slips in the
design of novel Josephson junction circuits, such
as topologically protected qubits, frequencyto-current
conversion devices or quantum
simulators.
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