Department: PIV

Theory of soft and living matter

Leader: M. Leonetti, P. Ronceray

Introduction

Nonlinear mechanics of biopolymer networks.

Principal investigator: P. Ronceray
PhD Student: Andonis Gerardos, Arthur Coët
Postdoc: Yuri Zhang

Networks of stiff, entangled biopolymers play a central role in the mechanical properties of biological matter, from the cell cytoskeleton to the extracellular matrix. Such networks contribute to the mechanical integrity of living matter, and permit force transmission from the motor protein to the tissue scale. Importantly, at the stress levels relevant to biology, the mechanical properties of these disordered assemblies of fibrous, quasi-one-dimensional objects are very different from usual elastic materials. Indeed, they tend to respond nonlinearly to stresses, due both to single filament properties and to emergent, collective deformation modes controlled by the connectivity and disorder of the network. Through simulations and collaborations with experimentalists, we study the fundamental nonlinear mechanical properties of biopolymer networks and their interplay with cell behavior. We aim to address the following question: When probing their complex environment, what do cells actually “feel”?

 

Inferring the dynamics of living matter.

Principal investigator: P. Ronceray
PhD Student: Andonis Gerardos, Arthur Coët
Postdoc: Yuri Zhang

Networks of stiff, entangled biopolymers play a central role in the mechanical properties of biological matter, from the cell cytoskeleton to the extracellular matrix. Such networks contribute to the mechanical integrity of living matter, and permit force transmission from the motor protein to the tissue scale. Importantly, at the stress levels relevant to biology, the mechanical properties of these disordered assemblies of fibrous, quasi-one-dimensional objects are very different from usual elastic materials. Indeed, they tend to respond nonlinearly to stresses, due both to single filament properties and to emergent, collective deformation modes controlled by the connectivity and disorder of the network. Through simulations and collaborations with experimentalists, we study the fundamental nonlinear mechanical properties of biopolymer networks and their interplay with cell behavior. We aim to address the following question: When probing their complex environment, what do cells actually “feel”?

 

Encapsulation

Principal investigateur: M. Leonetti

A - dynamics, shape, wrinkling and rupture of an elastic capsule

Doctorant: P. Regazzi

Funding: CNES

Encapsulation is a simple way of protecting, transporting and delivering internalized principles, but also of structuring space. This concerns very diverse fields such as food, cosmetics, new materials for construction or medicine. The capsules studied are droplets bounded by a thin polymer film (shell) and immersed in a liquid. The structural and mechanical properties of such objects are still poorly known: behaviour laws, elastic and viscous moduli, rupture, dynamics, etc. Indeed, there are few experimental results. The behavior of this closed elastic system is governed by the coupling at the interface between the viscous stress jump and the elastic response of the shell (also called skin or membrane depending on the domain).

We are interested in the rupture of capsules as a function of the nature of its membrane, the winkling/folding instabilities and the spatiotemporal dynamics of the shape by a multiscale analysis.

B – Interactions between capsules, collective behaviors

The strong deformation of capsules in flow induces more complex hydrodynamic interactions than between rigid particles. To this, it is necessary to add colloidal interactions as well as friction, key ingredients for the understanding of the rheology of rigid particle suspensions. We propose to study the implication of all these contributions to the case of binary interactions and more broadly in suspension.

 

 

Forme et dynamique de vésicules sous écoulement : théorie et simulation

Principal investigateur: M. Leonetti

Collaboration : P. G. Chen, M. Jaeger (M2P2, Marseille)

Souvent, l'objectif principal de la recherche sur l'adhésion cellulaire est d'identifier les protéines d'adhésion et les voies de signalisation pertinentes. Cependant, pour une description complète, il est essentiel de comprendre également la physique et la physico-chimie des processus qui régissent l'adhésion – ce qui n’est pas facile dans le contexte des complexités associées à une cellule vivante. Une façon de résoudre ce problème est d’utiliser des membranes modèles fonctionnalisées pour imiter la membrane cellulaire. Une percée importante a été l'intégration réussie de l’intégrine, protéine transmembranaire d’adhésion, dans des membranes lipidiques synthétiques. Nous sommes en train d'explorer de nouveaux protocoles pour fabriquer des vésicules dérivées de cellules qui contiennent les protéines d'adhésion transmembranaires endogènes.

Publications

2022

Stoichiometry Controls the Dynamics of Liquid Condensates of Associative Proteins

Pierre Ronceray, Yaojun Zhang, Xichong Liu, Ned Wingreen

Physical Review Letters 128:038102 (2022)10.1103/PhysRevLett.128.038102

2021

Self-organization and shape change by active polarization in nematic droplets

Fabian Jan Schwarzendahl, Pierre Ronceray, Kimberly Weirich, Kinjal Dasbiswas

Physical Review Research 3:043061 (2021)10.1103/PhysRevResearch.3.043061

Nucleation landscape of biomolecular condensates

Shunsuke Shimobayashi, Pierre Ronceray, David Sanders, Mikko Haataja, Clifford Brangwynne

Nature 599:503-506 (2021)10.1038/s41586-021-03905-5

Physical bioenergetics: Energy fluxes, budgets, and constraints in cells

Xingbo Yang, Matthias Heinemann, Jonathon Howard, Greg Huber, Srividya Iyer-Biswas, Guillaume Le Treut, Michael Lynch, Kristi L Montooth, Daniel J Needleman, Simone Pigolotti, Jonathan Rodenfels, Pierre Ronceray, Sadasivan Shankar, Iman Tavassoly, Shashi Thutupalli, Denis V Titov, Jin Wang, Peter J Foster

Proceedings of the National Academy of Sciences of the United States of America 118:e2026786118 (2021)10.1073/pnas.2026786118

2019

Fiber plucking by molecular motors yields large emergent contractility in stiff biopolymer networks

Pierre Ronceray, Chase P. Broedersz, Martin Lenz

Soft Matter 15:1481-1487 (2019)10.1039/c8sm00979a

Stress-dependent amplification of active forces in nonlinear elastic media

Pierre Ronceray, Chase Broedersz, Martin Lenz

Soft Matter 15:331-338 (2019)10.1039/c8sm00949j

2018

Cell contraction induces long-ranged stress stiffening in the extracellular matrix

Yu Long Han, Pierre Ronceray, Guoqiang Xu, Andrea Malandrino, Roger Kamm, Martin Lenz, Chase P. Broedersz, Ming Guo

Proceedings of the National Academy of Sciences of the United States of America 115:4075-4080 (2018)10.1073/pnas.1722619115

2016

Fiber networks amplify active stress

Pierre Ronceray, Chase Broedersz, Martin Lenz

Proceedings of the National Academy of Sciences of the United States of America 113:2827-2832 (2016)10.1073/pnas.1514208113

From liquid structure to configurational entropy: introducing structural covariance

Pierre Ronceray, Peter Harrowell

Journal of Statistical Mechanics: Theory and Experiment 2016:084002 (2016)

The free energy of a liquid when viewed as a population of overlapping clusters

Pierre Ronceray, Peter Harrowell

Molecular Simulation 42:1149-1156 (2016)10.1080/08927022.2015.1114180

Financement

• PI startup package CENTURI , 2021-26 Measuring and modeling soft living matter
• CENTURI 2023-2025, Understanding margination, from vessels to vascular networks