Date : 20/12/2011

Laboratory
PMMH
UMR 7636 CNRS / ESPCI / UPMC / Paris Diderot
ESPCI, 10 rue Vauquelin
75005 Paris
Website
Main discipline : Physics
Lab director : Philippe Petitjeans

PhD Supervisor
Julien Heuvingh
email : This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
phone: +33 1 40 79 47 08

Subjects
1.: Actin networks
2.: motility
3.: polymer mechanics

Tools and Methodologies
1.: video microscopy
2.: magnetic field
3.: reconstituted systems

Summary of lab's interests

PMMH main interests are hydrodynamics, soft and granular matter, statistical physics. Different teams work on subject between Biology and Physics, in areas such as animal flight, swim and motility at small scale, lipid membranes and mechanics of biological polymers.

Summary of project

Actin is one of the major building blocks of living cells. The actin protein polymerises into filaments organised in networks (cytoskeleton) which ensure the rigidity and deformability of the cell. Actin polymerisation generates forces used by the cell to migrate during development or cancer metastasis. Different actin networks in the cell assume different specific roles linked to their structure (reticulated or branched by different proteins, variable density and connectivity). We aim to unravel the link between these network organisation and cell mechanics. We developed a new technique to study in vitro the mechanics of reconstituted actin networks using dipolar attraction between magnetic beads. This technique allows the quantitative analysis of orders of magnitude more gels than what was previously possible. We showed a relationship between certain proteins involved in the growth of lamellipodium-like network and the mechanics of these gels. We also showed than in contrast with dilute crosslinked actin gels, the origin of elasticity is not due to the entropy of actin polymer chains but their mechanical deformation. The objective of the Phd project will be to advance further in the understanding of these networks and could develop in different ways : by studying the effect of proteins that reorganise the networks into crosslinked gels and study its effect on the microscopic origin of elasticity; to analyse the viscous response of the networks by using sinusoidal solicitation associated with a fast camera ; by forming gels on flat beads to infer the force needed to stall their growth, among others.

Interdisciplinarity of the project

This project is situated at the interface between Physics and cellular Biology and would thus be well suited for the FdV program.