Publications (en anglais)
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1. Articles scientifiques
 | Flexoelectric fluid membrane vesicles in spherical confinement
Niloufar Abtahi, Lila Bouzar, Nadia Saidi-Amroun, Martin Michael Müller |
Résumé
Plus d'infos
EPL, 131(1): 18001, 2020. Cf. aussi arXiv:2006.04475.
 | Isometric bending requires local constraints on free edges
Jemal Guven, Martin Michael Müller, Pablo Vázquez-Montejo |
Résumé
Plus d'infos
Math. Mech. Solids, 24: 4051, 2019. Cf. aussi arXiv:1904.05855.
 | Helical Superstructure of Intermediate Filaments
Lila Bouzar, Martin Michael Müller, René Messina, Bernd Nöding, Sarah Köster, Hervé Mohrbach, Igor M. Kulić |
Résumé
Plus d'infos
Phys. Rev. Lett., 122: 098101, 2019. Cf. aussi arXiv:1803.04691.
 | Vesicle dynamics in confined steady and harmonically modulated Poiseuille flows
Zakaria Boujja, Chaouqi Misbah, Hamid Ez-Zahraouy, Abdelilah Benyoussef, Thomas John, Christian Wagner, Martin Michael Müller |
We present a numerical study of the time-dependent motion of a membrane vesicle in a
channel under an imposed flow. In a Poiseuille flow the shape of the vesicle depends on the flow strength,
the mechanical properties of the membrane, and the width of the channel. In a wide parameter region, the
emerging snaking shape shows an oscillatory motion like a swimmer flagella even though the flow is
stationary. We quantify this behavior by the amplitude and frequency of the oscillations of the vesicle's
center of mass. The influence of an amplitude modulation of the imposed flow on the dynamics and shape of
the snaking vesicle is also investigated. We find that this modulation---when sufficiently small---induces
a modulation in amplitude and frequency of the center of mass of the snaking vesicle. For large
modulation amplitudes transitions to static shapes are observed.
 Fermer
Phys. Rev. E, 98: 043111, 2018. Cf. aussi arXiv:1810.04500.
 | Confining a fluid membrane vesicle of toroidal topology in an adhesive hard sphere
Lila Bouzar, Ferhat Menas, Martin Michael Müller |
Résumé
Plus d'infos
IOP Conf. Series: MSE, 186: 012021, 2017.
 | Squeezed helical elastica
Lila Bouzar, Martin Michael Müller, Pierre Gosselin, Igor M. Kulić, Hervé Mohrbach |
Résumé
Plus d'infos
Eur. Phys. J. E, 39: 114, 2016. Cf. aussi arXiv:1606.03611.
 | How bio-filaments twist membranes
Julien Fierling, Albert Johner, Igor M. Kulić, Hervé Mohrbach, Martin Michael Müller |
Résumé
Soft Matter, 12: 5747, 2016.
 | Toroidal membrane vesicles in spherical confinement
Lila Bouzar, Ferhat Menas, Martin Michael Müller |
Résumé
Plus d'infos
Phys. Rev. E, 92: 032721, 2015. Cf. aussi arXiv:1509.00765.
 | Non-linear buckling and symmetry breaking of a soft elastic sheet sliding on a cylindrical substrate
Norbert Stoop, Martin Michael Müller |
We consider the axial compression of a thin sheet wrapped around a rigid cylindrical substrate. In contrast to the wrinkling-to-fold transitions exhibited in similar systems, we find that the sheet always buckles into a single symmetric fold, while periodic solutions are unstable. Upon further compression, the solution breaks symmetry and stabilizes into a recumbent fold. Using linear analysis and numerics, we theoretically predict the buckling force and energy as a function of the compressive displacement. We compare our theory to experiments employing cylindrical neoprene sheets and find remarkably good agreement.
Fermer
Plus d'infos
Int. J. Non-Linear Mech., 75: 115, 2015. Cf. aussi arXiv:1503.05030.
 | Crunching Biofilament Rings
Julien Fierling, Martin Michael Müller, Hervé Mohrbach, Albert Johner, Igor M. Kulić |
Résumé
Plus d'infos
Europhys. Lett., 107(6): 68002, 2014. Cf. aussi arXiv:1408.6787.
 | Confotronic dynamics of tubular filaments
Osman Kahraman, Hervé Mohrbach, Martin Michael Müller, Igor M. Kulić |
Résumé
Plus d'infos
Soft Matter, 10(16): pp. 2836-2847, 2014. Cf. aussi arXiv:1312.3106.
 | Whirling skirts and rotating cones
Jemal Guven, J. A. Hanna, Martin Michael Müller |
Résumé
New J. Phys., 15: 113055, 2013. Cf. aussi arXiv:1306.2619.
 | Myotubularin and PtdIns3P remodel the sarcoplasmic reticulum in muscle in vivo
Leonela Amoasii, Karim Hnia, Gaëtan Chicanne, Andreas Brech, Belinda Simone Cowling, Martin Michael Müller, Yannick Schwab, Pascale Koebel, Arnaud Ferry, Bernard Payrastre, Jocelyn Laporte |
The sarcoplasmic reticulum (SR) is a specialized form of endoplasmic reticulum (ER) in skeletal muscle
and is essential for calcium homeostasis. The mechanisms involved in SR
remodeling and maintenance of SR subdomains are elusive. In this study, we identified
myotubularin (MTM1), a phosphatase mutated in X-linked centronuclear myopathy
(XLCNM), as a key regulator of phosphoinositide-3-monophosphate (PtdIns3P) levels at the
SR. Mtm1 deficient mouse muscles and myoblasts from XLCNM patients exhibit abnormal
SR/ER networks. In vivo modulation of MTM1 enzymatic activity in muscle using ectopic
expression of wild-type or a dead-phosphatase MTM1 protein leads to differential SR
remodeling. Active MTM1 is associated to flat membrane stacks, while dead-phosphatase
MTM1 mutant promotes highly curved cubic membranes originating from the SR and
enriched in PtdIns3P. Moreover, expression of the PtdIns3P binding module 2XFYVE also
modified the SR shape at triads. Our findings, supported by the parallel analysis of the Mtm1-
null mouse and in vivo study, reveal a direct function of MTM1 enzymatic activity in SR
remodeling and a key role for its substrate PtdIns3P in promoting SR membrane curvature in
skeletal muscle. We propose that alteration in SR remodeling is a primary cause of X-linked
centronuclear myopathy. The tight regulation of PtdIns3P on specific membrane subdomains
may be a general mechanism to control membrane curvature.
Fermer
J. Cell Sci., 126(8): 1806, 2013.
 | Dipoles in thin sheets
Jemal Guven, J. A. Hanna, Osman Kahraman, Martin Michael Müller |
A flat elastic sheet may contain pointlike conical singularities that carry a metrical "charge" of Gaussian curvature. Adding such elementary defects to a sheet allows one to make many shapes, in a manner broadly
analogous to the familiar multipole construction in electrostatics. However, here the underlying field theory is non-linear,
and superposition of intrinsic defects is non-trivial as it must respect the immersion of the resulting surface in three
dimensions. We consider a "charge-neutral" dipole composed of two conical singularities of opposite sign.
Unlike the relatively simple electrostatic case, here there are two distinct stable minima and an infinity of unstable equilibria.
We determine the shapes of the minima and evaluate their energies in the thin-sheet regime where bending dominates
over stretching. Our predictions are in surprisingly good agreement with experiments on paper sheets.
Fermer
Plus d'infos
Eur. Phys. J. E, 36: 106, 2013. Cf. aussi arXiv:1212.3262.
 | Fluid membrane vesicles in confinement
Osman Kahraman, Norbert Stoop, Martin Michael Müller |
Résumé
Plus d'infos
New J. Phys., 14: 095021, 2012.
 | Petal shapes of sympetaleous flowers: the interplay between growth, geometry and elasticity
Martine Ben Amar, Martin Michael Müller, Miguel Trejo |
Résumé
Plus d'infos
New J. Phys., 14: 085014, 2012. Choisi pour les Highlights of 2012.
 | Morphogenesis of membrane invaginations in spherical confinement
Osman Kahraman, Norbert Stoop, Martin Michael Müller |
Résumé
Plus d'infos
Europhys. Lett., 97(6): 68008, 2012. Cf. aussi arXiv:1201.2518.
 | Conical instabilities on paper
Jemal Guven, Martin Michael Müller, Pablo Vázquez-Montejo |
Résumé
Plus d'infos
J. Phys. A: Math. Theor., 45(1): 015203, 2012. Cf. aussi arXiv:1107.5008.
 | Interface-mediated interactions: Entropic forces of curved membranes
Pierre Gosselin, Hervé Mohrbach, Martin Michael Müller |
Particles embedded in a fluctuating interface experience forces and torques
mediated by the deformations and by the thermal fluctuations of the medium.
Considering a system of two cylinders bound to a fluid membrane we show that
the entropic contribution enhances the curvature-mediated repulsion between
the two cylinders. This is contrary to the usual attractive Casimir force in
the absence of curvature-mediated interactions. For a large distance between
the cylinders, we retrieve the renormalization of the surface tension of a
flat membrane due to thermal fluctuations.
Fermer
Plus d'infos
Phys. Rev. E, 83(5): 051921, 2011. Cf. aussi arXiv:1011.1221.
 | Self-Contact and Instabilities in the Anisotropic Growth of Elastic Membranes
Norbert Stoop, Falk K. Wittel, Martine Ben Amar, Martin Michael Müller, Hans J. Herrmann |
We investigate the morphology of thin discs and rings growing in circumferential direction. Recent analytical results suggest that this growth produces symmetric excess cones (e-cones). We study the stability of such solutions considering self-contact and bending stress. We show that, contrary to what was assumed in previous analytical solutions, beyond a critical growth factor, no symmetric e-cone solution is energetically minimal any more. Instead, we obtain skewed e-cone solutions having lower energy, characterized by a skewness angle and repetitive spiral winding with increasing growth. These results are generalized to discs with varying thickness and rings with holes of different radii.
Fermer
Plus d'infos
Phys. Rev. Lett., 105(6): 068101, 2010. Cf. aussi arXiv:1007.1871.
 | Cell Model Approach to Membrane Mediated Protein Interactions
Martin Michael Müller, Markus Deserno |
Résumé
Plus d'infos
Prog. Theor. Phys. Suppl., 184: pp. 351-363, 2010.
 | Hamiltonian formulation of surfaces with constant Gaussian curvature
Miguel Trejo, Martine Ben Amar, Martin Michael Müller |
Dirac's method for constrained Hamiltonian systems is used to describe surfaces of constant Gaussian curvature. A geometrical free energy, for which these surfaces are equilibrium states, is introduced and interpreted as an action. An equilibrium surface can then be generated by the evolution of a closed space curve.
Since the underlying action depends on second derivatives, the velocity of the curve and its conjugate momentum must be included in the set of phase space variables. Furthermore, the action is linear in the acceleration of the curve and possesses a local symmetry---reparametrization invariance---which implies primary constraints in the canonical formalism. These constraints are incorporated into the Hamiltonian through Lagrange multiplier functions, that are identified as the components of the acceleration of the curve. The formulation leads to four first order partial differential equations, one for each canonical variable.
With the appropriate choice of parametrization only one of these equations has to be solved to obtain the surface which is swept out by the evolving space curve. To illustrate the formalism, several evolutions of pseudospherical surfaces are discussed.
Fermer
Plus d'infos
J. Phys. A: Math. Theor., 42(42): 425204, 2009.
 | Local Membrane Mechanics of Pore-Spanning Bilayers
Ingo Mey, Milena Stephan, Eva K. Schmitt, Martin Michael Müller, Martine Ben Amar, Claudia Steinem, Andreas Janshoff |
Résumé
Plus d'infos
J. Am. Chem. Soc., 131(20): pp. 7031-7039, 2009.
 | Elasticity Mapping of Pore-Suspending Native Cell Membranes
Bärbel Lorenz, Ingo Mey, Siegfried Steltenkamp, Tamir Fine, Christina Rommel, Martin Michael Müller, Alexander Maiwald, Joachim Wegener, Claudia Steinem, Andreas Janshoff |
Résumé
Plus d'infos
Small, 5(7): pp. 832-838, 2009.
 | Conical Defects in Growing Sheets
Martin Michael Müller, Martine Ben Amar, Jemal Guven |
Résumé
Plus d'infos
Phys. Rev. Lett., 101(15): 156104, 2008. Cf. aussi arXiv:0807.1814.
 | How paper folds: bending with local constraints
Jemal Guven, Martin Michael Müller |
A variational framework is introduced to describe how a surface bends when it is subject to local constraints on its geometry. This framework is applied to describe the patterns of a folded sheet of paper. The unstretchability of paper implies a constraint on the surface metric; bending is penalized by an energy quadratic in mean curvature. The local Lagrange multipliers enforcing the constraint are identified with a conserved tangential stress that couples to the extrinsic curvature of the sheet. The framework is illustrated by examining the deformation of a flat sheet into a generalized cone.
Fermer
Plus d'infos
J. Phys. A: Math. Theor., 41(5): 055203, 2008. Cf. aussi arXiv:0712.0978.
 | Contact lines for fluid surface adhesion
Markus Deserno, Martin Michael Müller, Jemal Guven |
Résumé
Plus d'infos
Phys. Rev. E, 76(1): 011605, 2007. Cf. aussi cond-mat/0703019.
Choisi pour le Virtual Journal of Biological Physics Research.
 | Balancing torques in membrane-mediated interactions: Exact results and
numerical illustrations
Martin Michael Müller, Markus Deserno, Jemal Guven |
Torques on interfaces can be described by a divergence-free tensor
which is fully encoded in the geometry. This tensor consists of two
terms, one originating in the couple of the stress, the other capturing
an intrinsic contribution due to curvature. In analogy to the description
of forces in terms of a stress tensor, the torque on a particle can be
expressed as a line integral along any contour surrounding the particle.
Interactions between particles mediated by a fluid membrane are studied
within this framework. In particular, torque balance places a strong
constraint on the shape of the membrane. Symmetric two-particle
configurations admit simple analytical expressions which are valid
in the fully nonlinear regime; in particular, the problem may be
solved exactly in the case of two membrane-bound parallel cylinders.
This apparently simple system provides some flavor of the remarkably
subtle nonlinear behavior associated with membrane-mediated interactions.
Fermer
Plus d'infos
Phys. Rev. E, 76(1): 011921, 2007. Cf. aussi cond-mat/0702340.
Choisi pour le Virtual Journal of Biological Physics Research.
 | Aggregation and vesiculation of membrane proteins by curvature-mediated
interactions
Benedict J. Reynwar, Gregoria Illya, Vagelis A. Harmandaris, Martin Michael Müller, Kurt Kremer, Markus Deserno |
Membrane remodelling plays an important role in cellular tasks such as endocytosis, vesiculation and protein sorting, and in the biogenesis of organelles such as the endoplasmic reticulum or the Golgi apparatus. It is well established that the remodelling process is aided by specialized proteins that can sense as well as create membrane curvature, and trigger tubulation when added to synthetic liposomes. Because the energy needed for such large-scale changes in membrane geometry significantly exceeds the binding energy between individual proteins and between protein and membrane, cooperative action is essential. It has recently been suggested that curvature-mediated attractive interactions could aid cooperation and complement the effects of specific binding events on membrane remodelling. But it is difficult to experimentally isolate curvature-mediated interactions from direct attractions between proteins. Moreover, approximate theories predict repulsion between isotropically curving proteins. Here we use coarse-grained membrane simulations to show that curvature-inducing model proteins adsorbed on lipid bilayer membranes can experience attractive interactions that arise purely as a result of membrane curvature. We find that once a minimal local bending is realized, the effect robustly drives protein cluster formation and subsequent transformation into vesicles with radii that correlate with the local curvature imprint. Owing to its universal nature, curvature-mediated attraction can operate even between proteins lacking any specific interactions, such as newly synthesized and still immature membrane proteins in the endoplasmic reticulum.
Fermer
Plus d'infos
Nature 447(7143): pp. 461-464, 2007.
 | How to determine local elastic properties of lipid bilayer membranes
from atomic-force-microscope measurements: A theoretical analysis
Davood Norouzi, Martin Michael Müller, Markus Deserno |
Résumé
Plus d'infos
Phys. Rev. E, 74(6): 061914, 2006. Cf. aussi cond-mat/0602662.
Choisi pour le Virtual Journal of Biological Physics Research.
 | Mechanical Properties of Pore-Spanning Lipid Bilayers Probed by Atomic Force Microscopy
Siegfried Steltenkamp, Martin Michael Müller, Markus Deserno, Christian Hennesthal, Claudia Steinem, Andreas Janshoff |
We measure the elastic response of a free-standing lipid membrane to a local indentation by using an atomic force microscope. Starting point is a planar
gold-coated alumina substrate with a chemisorbed 3-mercaptopropionic acid
monolayer displaying circular pores of very well defined and tunable size, over
which bilayers composed of N,N,- dimethyl- N,N,- dioctadecylammonium bromide or
1,2 - dioleoyl - 3 - trimethylammonium - propane chloride were spread.
Centrally indenting these 'nanodrums' with an atomic force microscope tip yields
force-indentation curves, which we quantitatively analyze by solving the
corresponding shape equations of continuum curvature elasticity. Since the
measured response depends in a known way on the system geometry (pore size, tip
radius) and on material parameters (bending modulus, lateral tension), this opens
the possibility to monitor local elastic properties of lipid membranes in a
well-controlled setting.
Fermer
Plus d'infos
Biophys. J., 91(1): pp. 217-226, 2006.
 | Interface mediated interactions between particles -- a geometrical approach
Martin Michael Müller, Markus Deserno, Jemal Guven |
Résumé
Plus d'infos
Phys. Rev. E, 72(6): 061407, 2005. Cf. aussi cond-mat/0506019.
Choisi pour le Virtual Journal of Biological Physics Research.
 | Geometry of surface-mediated interactions
Martin Michael Müller, Markus Deserno, Jemal Guven |
Soft interfaces can mediate interactions between particles bound to
them. The force transmitted through the surface geometry on a
particle may be expressed as a closed line integral of the surface
stress tensor around that particle. This contour may be deformed to
exploit the symmetries present; for two identical particles, one
obtains an exact expression for the force between them in terms of
the local surface geometry of their mid-plane; in the case of a
fluid membrane the sign of the interaction is often evident. The
approach, by construction, is adapted directly to the surface and is
independent of its parameterization. Furthermore, it is applicable
for arbitrarily large deformations; in particular, it remains valid
beyond the linear small-gradient regime.
Fermer
Plus d'infos
Europhys. Lett., 69(3): pp. 482-488, 2005. Cf. aussi cond-mat/0409043.
2. Livres
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New Trends in the Physics and Mechanics of Biological Systems
Lecture Notes of the Les Houches Summer School, vol. 92 (Oxford University Press, 2011),
éd. par Martine Ben Amar, Alain Goriely, Martin Michael Müller et Leticia Cugliandolo.
Chapitre 9 :
The physics of the cell membrane
Martin Michael Müller et Martine Ben Amar.
3. Mémoires
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Theoretical examinations of interface mediated interactions between colloidal particles,
mémoire (2004).
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Theoretical studies of fluid membrane mechanics, thèse de doctorat (2007).
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Symmetry breaking in bioelasticity, thèse d'habilitation à diriger des recherches (2015).
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