Past Seminars

Here is the list of our past seminars:


Julien Heuvingh (PMMH, ESPCI). ESPCI-ENS biophysics seminar - Antonin EDDI, Benoit Semin, Etienne Reyssat, Natasa Ilic, Olivia Du Roure, Sylvain Patinet

What we learn about the dynamics of actin by growing it from
cylinders, stars and diamonds

Actin is a major component of biological cells and forms filaments
that constantly polymerize and depolymerize. This activity is used by
the cell to generate forces in order to crawl on a surface or to pinch
part of its membrane during endocytosis. The cortex, a dense actin
network, endows its viscoelastic properties to the cell and protects
it from unwanted deformations. The in vitro reconstitution of dense
actin networks on micron-size spheres was a seminal step to understand
these processes. Here I will describe two experiments where we
reconstituted actin networks around non-spherical micro-objects. In
the first one, actin grows from the faces of magnetic cylinders
arranged in a string. A load is applied by the attraction of
neighboring cylinders to monitor the actin network's growth under
stress and measure its elasticity. We evidenced a peculiar non-linear
elastic behavior of the network and a direct interaction between
growth velocity and viscoelastic behavior. In the second experiment,
we revisit the problem of the symmetry breaking occurring in an actin
gel growing from a spherical object by growing the actin from star and
diamond-shaped prisms. I will show unexpected results on where the
fracture arises that downplay the role of mechanical stress in this
phenomenon.






Recent seminars  (0)


Julien Heuvingh (PMMH, ESPCI). ESPCI-ENS biophysics seminar - Antonin EDDI, Benoit Semin, Etienne Reyssat, Natasa Ilic, Olivia Du Roure, Sylvain Patinet

What we learn about the dynamics of actin by growing it from
cylinders, stars and diamonds

Actin is a major component of biological cells and forms filaments
that constantly polymerize and depolymerize. This activity is used by
the cell to generate forces in order to crawl on a surface or to pinch
part of its membrane during endocytosis. The cortex, a dense actin
network, endows its viscoelastic properties to the cell and protects
it from unwanted deformations. The in vitro reconstitution of dense
actin networks on micron-size spheres was a seminal step to understand
these processes. Here I will describe two experiments where we
reconstituted actin networks around non-spherical micro-objects. In
the first one, actin grows from the faces of magnetic cylinders
arranged in a string. A load is applied by the attraction of
neighboring cylinders to monitor the actin network's growth under
stress and measure its elasticity. We evidenced a peculiar non-linear
elastic behavior of the network and a direct interaction between
growth velocity and viscoelastic behavior. In the second experiment,
we revisit the problem of the symmetry breaking occurring in an actin
gel growing from a spherical object by growing the actin from star and
diamond-shaped prisms. I will show unexpected results on where the
fracture arises that downplay the role of mechanical stress in this
phenomenon.






Seminar archive  (219)


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