Publications
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Articles in scientific journals
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Books
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Theses
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1. Articles in scientific journals
![](grafiken/33flexoelectric_icon.png) | Flexoelectric fluid membrane vesicles in spherical confinement
Niloufar Abtahi, Lila Bouzar, Nadia Saidi-Amroun, Martin Michael Müller |
The morphology of spherically confined flexoelectric fluid membrane vesicles in an ex-
ternal uniform electric field is studied numerically. Due to the deformations induced by
the confinement, the membrane becomes polarized resulting in an interaction with the
external field. The equilibrium shapes of the vesicle without electric field can be clas-
sified in a geometrical phase diagram as a function of scaled area and reduced volume
[1, 2]. When the area of the membrane is only slightly larger than the area of the con-
fining sphere, a single axisymmetric invagination appears. A non-vanishing electric field
induces an additional elongation of the confined vesicle which is either perpendicular or
parallel depending on the sign of the electric field parameter. Higher values of the surface
area or the electric field parameter can reduce the symmetry of the system leading to
more complex folding. We present the resulting shapes and show that transition lines
are shifted in the presence of an electric field. The obtained folding patterns could be of
interest for biophysical and technological applications alike.
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EPL, 131(1): 18001, 2020. See also arXiv:2006.04475.
![](grafiken/32tangentdev_icon.png) | Isometric bending requires local constraints on free edges
Jemal Guven, Martin Michael Müller, Pablo Vázquez-Montejo |
While the shape equations describing the equilibrium of an unstretchable thin sheet that is free
to bend are known, the boundary conditions that supplement these equations on free edges have remained elusive.
Intuitively, unstretchability is captured by a constraint on the metric within the bulk. Naïvely one would then
guess that this constraint is enough to ensure that the deformations determining the boundary conditions on these
edges respect the isometry constraint. If matters were this simple, unfortunately, it would imply unbalanced torques
(as well as forces) along the edge unless manifestly unphysical constraints are met by the boundary geometry. In this
article, we identify the source of the problem: not only the local arc-length but also the geodesic curvature need to
be constrained explicitly on all free edges. We derive the boundary conditions which follow. In contrast to conventional
wisdom, there is no need to introduce boundary layers. This framework is applied to isolated conical defects, both
with deficit as well, but more briefly, as surplus angles. Using these boundary conditions, we show that the lateral
tension within a circular cone of fixed radius is equal but opposite to the radial compression, and independent of
the deficit angle itself. We proceed to examine the effect of an oblique outer edge on this cone perturbatively
demonstrating that both the correction to the geometry as well as the stress distribution in the cone kicks in at
second order in the eccentricity of the edge.
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Math. Mech. Solids, 24: 4051, 2019. See also arXiv:1904.05855.
![](grafiken/31squeelixsimulations_icon.jpg) | Helical Superstructure of Intermediate Filaments
Lila Bouzar, Martin Michael Müller, René Messina, Bernd Nöding, Sarah Köster, Hervé Mohrbach, Igor M. Kulić |
Abstract
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Phys. Rev. Lett., 122: 098101, 2019. See also arXiv:1803.04691.
![](grafiken/30vesicleflow_icon.png) | 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 |
Abstract
Phys. Rev. E, 98: 043111, 2018. See also arXiv:1810.04500.
![](grafiken/29confinementtorusadhesion_icon.png) | Confining a fluid membrane vesicle of toroidal topology in an adhesive hard sphere
Lila Bouzar, Ferhat Menas, Martin Michael Müller |
Abstract
Read more
IOP Conf. Series: MSE, 186: 012021, 2017.
![](grafiken/28squeelix_icon.png) | Squeezed helical elastica
Lila Bouzar, Martin Michael Müller, Pierre Gosselin, Igor M. Kulić, Hervé Mohrbach |
We theoretically study the conformations of a helical semi-flexible filament
confined to a two-dimensional surface. This squeezed helix exhibits a variety of unexpected shapes
resembling circles, waves or spirals depending on the material parameters. We explore the conformation
space in detail and show that the shapes can be understood as the mutual elastic interaction of
conformational quasi-particles. Our theoretical results are potentially useful to
determine the material parameters of such helical filaments in an experimental setting.
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Eur. Phys. J. E, 39: 114, 2016. See also arXiv:1606.03611.
![](grafiken/27dynamin_icon.png) | How bio-filaments twist membranes
Julien Fierling, Albert Johner, Igor M. Kulić, Hervé Mohrbach, Martin Michael Müller |
We study the deformations of a fluid membrane imposed by adhering stiff
bio-filaments due to the torques they apply. In the limit of small deformations, we
derive a general expression for the energy and the deformation field of the membrane.
This expression is specialised to different important cases including closed and helical
bio-filaments. In particular, we analyse interface-mediated interactions and membrane
wrapping when the filaments apply a local torque distribution on a tubular membrane.
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Soft Matter, 12: 5747, 2016.
![](grafiken/26confinementtorus_icon.png) | Toroidal membrane vesicles in spherical confinement
Lila Bouzar, Ferhat Menas, Martin Michael Müller |
Abstract
Read more
Phys. Rev. E, 92: 032721, 2015. See also arXiv:1509.00765.
![](grafiken/25sleeve_icon.png) | Non-linear buckling and symmetry breaking of a soft elastic sheet sliding on a cylindrical substrate
Norbert Stoop, Martin Michael Müller |
Abstract
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Int. J. Non-Linear Mech., 75: 115, 2015. See also arXiv:1503.05030.
![](grafiken/24dynamin_icon.jpg) | Crunching Biofilament Rings
Julien Fierling, Martin Michael Müller, Hervé Mohrbach, Albert Johner, Igor M. Kulić |
Abstract
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Europhys. Lett., 107(6): 68002, 2014. See also arXiv:1408.6787.
![](grafiken/23microtubules_icon.png) | Confotronic dynamics of tubular filaments
Osman Kahraman, Hervé Mohrbach, Martin Michael Müller, Igor M. Kulić |
Abstract
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Soft Matter, 10(16): pp. 2836-2847, 2014. See also arXiv:1312.3106.
![](grafiken/22rotation_icon.png) | Whirling skirts and rotating cones
Jemal Guven, J. A. Hanna, Martin Michael Müller |
Abstract
New J. Phys., 15: 113055, 2013. See also arXiv:1306.2619.
![](grafiken/21cubicmembranes_icon.png) | 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.
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J. Cell Sci., 126(8): 1806, 2013.
![](grafiken/20epole_icon.png) | Dipoles in thin sheets
Jemal Guven, J. A. Hanna, Osman Kahraman, Martin Michael Müller |
Abstract
Read more
Eur. Phys. J. E, 36: 106, 2013. See also arXiv:1212.3262.
![](grafiken/19confinement_icon.png) | Fluid membrane vesicles in confinement
Osman Kahraman, Norbert Stoop, Martin Michael Müller |
Abstract
Read more
New J. Phys., 14: 095021, 2012.
![](grafiken/18flowermorpho_icon.png) | Petal shapes of sympetaleous flowers: the interplay between growth, geometry and elasticity
Martine Ben Amar, Martin Michael Müller, Miguel Trejo |
The growth of a thin elastic sheet imposes constraints on its geometry such as its Gaussian curvature KG.
In this paper, we construct the shapes of sympetalous bell-shaped flowers with a constant Gaussian curvature. Minimizing the bending energies
of both the petal and the veins, we are able to predict quantitatively the global shape of these flowers. We discuss two toy problems
where the Gaussian curvature is either negative or positive. In the former case the axisymmetric pseudosphere turns out to mimic the correct
shape before edge curling; in the latter case, singularities of the mathematical surface coincide with strong veins. Using a variational
minimization of the elastic energy, we find that the optimal number for the veins is either four, five or six, a number which is deceptively
close to the statistics on real flowers in nature.
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New J. Phys., 14: 085014, 2012. Also featured in the Highlights of 2012.
![](grafiken/17confinement_icon.png) | Morphogenesis of membrane invaginations in spherical confinement
Osman Kahraman, Norbert Stoop, Martin Michael Müller |
Abstract
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Europhys. Lett., 97(6): 68008, 2012. See also arXiv:1201.2518.
![](grafiken/16econeunstab_icon.jpg) | Conical instabilities on paper
Jemal Guven, Martin Michael Müller, Pablo Vázquez-Montejo |
Abstract
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J. Phys. A: Math. Theor., 45(1): 015203, 2012. See also arXiv:1107.5008.
![](grafiken/15casimir_icon.png) | 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.
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Phys. Rev. E, 83(5): 051921, 2011. See also arXiv:1011.1221.
![](grafiken/14econetouch_icon.jpg) | 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 |
Abstract
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Phys. Rev. Lett., 105(6): 068101, 2010. See also arXiv:1007.1871.
![](grafiken/13cellmodel_icon.png) | Cell Model Approach to Membrane Mediated Protein Interactions
Martin Michael Müller, Markus Deserno |
Abstract
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Prog. Theor. Phys. Suppl., 184: pp. 351-363, 2010.
![](grafiken/12pseudo_icon.jpg) | Hamiltonian formulation of surfaces with constant Gaussian curvature
Miguel Trejo, Martine Ben Amar, Martin Michael Müller |
Abstract
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J. Phys. A: Math. Theor., 42(42): 425204, 2009.
![](grafiken/11indentstretch_icon.jpg) | Local Membrane Mechanics of Pore-Spanning Bilayers
Ingo Mey, Milena Stephan, Eva K. Schmitt, Martin Michael Müller, Martine Ben Amar, Claudia Steinem, Andreas Janshoff |
The mechanical behavior of lipid bilayers spanning the pores of highly ordered porous silicon substrates was studied by local indentation experiments as a function of surface functionalization, lipid composition, solvent content, indentation velocity, and pore radius. Solvent-containing nanoblack lipid membranes (nano-BLMs) as well as solvent-free pore-spanning bilayers were imaged by fluorescence and atomic force microscopy prior to force curve acquisition, which allows distinguishing between membrane-covered and uncovered pores. Force indentation curves on pore-spanning bilayers attached to functionalized hydrophobic porous silicon substrates reveal a predominately linear response that is mainly attributed to prestress in the membranes. This is in agreement with the observation that indentation leads to membrane lysis well below 5% area dilatation. However, membrane bending and lateral tension dominates over
prestress and stretching if solvent-free supported membranes obtained from spreading giant liposomes on hydrophilic porous silicon are indented.
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J. Am. Chem. Soc., 131(20): pp. 7031-7039, 2009.
![](grafiken/10substrate_icon.jpg) | 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 |
The mechanics of cellular membranes is governed by a non-equilibrium composite framework
consisting of the semiflexible filamentous cytoskeleton and extracellular matrix proteins linked to
the lipid bilayer. While elasticity information of plasma membranes has mainly been obtained from
whole cell analysis, techniques that allow to address local mechanical properties of cell
membranes are desirable to learn how their lipid and protein composition is reflected in the elastic
behavior on local length scales. Here, we introduce an approach based on basolateral
membranes of polar epithelial Madin-Darby canine kidney (MDCK) II cells, prepared on a highly ordered porous substrate that
allows elastic mapping on a submicrometer length scale. A strong correlation between the
density of actin filaments and the measured membrane elasticity is found. Spatially resolved indentation experiments carried out with atomic force and fluorescence microscope permit to relate the supramolecular structure to the elasticity of cellular membranes. It is shown that the elastic response of the pore-spanning cell membranes is governed by the local bending modules rather than the lateral tension.
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Small, 5(7): pp. 832-838, 2009.
![](grafiken/09econe_icon.png) | Conical Defects in Growing Sheets
Martin Michael Müller, Martine Ben Amar, Jemal Guven |
A growing or shrinking disc will adopt a conical shape, its intrinsic geometry characterized by a surplus angle φe at the apex. If growth is slow, the cone will find its equilibrium. Whereas this is trivial if φe≤0, the disc can fold into one of a discrete infinite number of states if φe is positive. We construct these states in the regime where bending dominates, determine their energies and how stress is distributed in them. For each state a critical value of φe is identified beyond which the cone touches itself. Before this occurs, all states are stable; the ground state has twofold symmetry.
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Phys. Rev. Lett., 101(15): 156104, 2008. See also arXiv:0807.1814.
![](grafiken/08drape_icon.png) | 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.
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J. Phys. A: Math. Theor., 41(5): 055203, 2008. See also arXiv:0712.0978.
![](grafiken/07vesad_icon.jpg) | Contact lines for fluid surface adhesion
Markus Deserno, Martin Michael Müller, Jemal Guven |
Abstract
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Phys. Rev. E, 76(1): 011605, 2007. See also cond-mat/0703019. Also featured in the Virtual Journal of Biological Physics Research.
![](grafiken/06Eulerelastica_icon.png) | Balancing torques in membrane-mediated interactions: Exact results and
numerical illustrations
Martin Michael Müller, Markus Deserno, Jemal Guven |
Abstract
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Phys. Rev. E, 76(1): 011921, 2007. See also cond-mat/0702340. Also featured in the Virtual Journal of Biological Physics Research.
![](grafiken/05curvemedcover_icon.jpg) | 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 |
Abstract
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Nature 447(7143): pp. 461-464, 2007.
![](grafiken/04tip_icon.jpg) | 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 |
Abstract
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Phys. Rev. E, 74(6): 061914, 2006. See also cond-mat/0602662. Also featured in the Virtual Journal of Biological Physics Research.
![](grafiken/03DODAB_icon.png) | 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 |
Abstract
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Biophys. J., 91(1): pp. 217-226, 2006.
![](grafiken/02multibody_icon.gif) | Interface mediated interactions between particles -- a geometrical approach
Martin Michael Müller, Markus Deserno, Jemal Guven |
Particles bound to an interface interact because they deform its shape.
The stresses that result are fully encoded in the geometry and described
by a divergence-free surface stress tensor. This stress tensor can be
used to express the force on a particle as a line integral along any
conveniently chosen closed contour that surrounds the particle. The
resulting expression is exact (i.e., free of any 'smallness' assumptions)
and independent of the chosen surface parametrization. Additional surface
degrees of freedom, such as vector fields describing lipid tilt, are readily
included in this formalism. As an illustration, we derive the exact force
for several important surface Hamiltonians in various symmetric two-particle
configurations in terms of the midplane geometry; its sign is evident in
certain interesting limits. Specializing to the linear regime, where the
shape can be analytically determined, these general expressions yield
force-distance relations, several of which have originally been derived
by using an energy based approach.
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Phys. Rev. E, 72(6): 061407, 2005. See also cond-mat/0506019. Also featured in the Virtual Journal of Biological Physics Research.
![](grafiken/01surfacemed_icon.jpg) | Geometry of surface-mediated interactions
Martin Michael Müller, Markus Deserno, Jemal Guven |
Abstract
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Europhys. Lett., 69(3): pp. 482-488, 2005. See also cond-mat/0409043.
2. Books
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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),
edited by Martine Ben Amar, Alain Goriely, Martin Michael Müller and Leticia Cugliandolo.
Chapter 9:
The physics of the cell membrane
Martin Michael Müller and Martine Ben Amar.
3. Theses
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Theoretical examinations of interface mediated interactions between colloidal particles,
diploma thesis (2004).
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Theoretical studies of fluid membrane mechanics, dissertation (2007).
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Symmetry breaking in bioelasticity, habilitation thesis (2015).
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