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Article ; Online: Chiral self-sorting of active semiflexible filaments with intrinsic curvature.

Moore, Jeffrey M / Glaser, Matthew A / Betterton, Meredith D

2021 Volume 17, Issue 17, Page(s) 4559–4565

Abstract: Many-body interactions in systems of active matter can cause particles to move collectively and self-organize into dynamic structures with long-range order. In cells, the self-assembly of cytoskeletal filaments is critical for cellular motility, ... ...

Abstract	Many-body interactions in systems of active matter can cause particles to move collectively and self-organize into dynamic structures with long-range order. In cells, the self-assembly of cytoskeletal filaments is critical for cellular motility, structure, intracellular transport, and division. Semiflexible cytoskeletal filaments driven by polymerization or motor-protein interactions on a two-dimensional substrate, such as the cell cortex, can induce filament bending and curvature leading to interesting collective behavior. For example, the bacterial cell-division filament FtsZ is known to have intrinsic curvature that causes it to self-organize into rings and vortices, and recent experiments reconstituting the collective motion of microtubules driven by motor proteins on a surface have observed chiral symmetry breaking of the collective behavior due to motor-induced curvature of the filaments. Previous work on the self-organization of driven filament systems have not studied the effects of curvature and filament structure on collective behavior. In this work, we present Brownian dynamics simulation results of driven semiflexible filaments with intrinsic curvature and investigate how the interplay between filament rigidity and radius of curvature can tune the self-organization behavior in homochiral systems and heterochiral mixtures. We find a curvature-induced reorganization from polar flocks to self-sorted chiral clusters, which is modified by filament flexibility. This transition changes filament transport from ballistic to diffusive at long timescales.
Language	English
Publishing date	2021-05-04
Publishing country	England
Document type	Journal Article
ZDB-ID	2191476-X
ISSN	1744-6848 ; 1744-683X
ISSN (online)	1744-6848
ISSN	1744-683X
DOI	10.1039/d0sm01163k
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Article: Active condensation of filaments under spatial confinement.

Ansari, Saad / Yan, Wen / Lamson, Adam / Shelley, Michael J / Glaser, Matthew A / Betterton, Meredith D

Frontiers in physics

2022 Volume 10

Abstract: Living systems exhibit self-organization, a phenomenon that enables organisms to perform functions essential for life. The interior of living cells is a crowded environment in which the self-assembly of cytoskeletal networks is spatially constrained by ... ...

Abstract	Living systems exhibit self-organization, a phenomenon that enables organisms to perform functions essential for life. The interior of living cells is a crowded environment in which the self-assembly of cytoskeletal networks is spatially constrained by membranes and organelles. Cytoskeletal filaments undergo active condensation in the presence of crosslinking motor proteins. In past studies, confinement has been shown to alter the morphology of active condensates. Here, we perform simulations to explore systems of filaments and crosslinking motors in a variety of confining geometries. We simulate spatial confinement imposed by hard spherical, cylindrical, and planar boundaries. These systems exhibit non-equilibrium condensation behavior where crosslinking motors condense a fraction of the overall filament population, leading to coexistence of vapor and condensed states. We find that the confinement lengthscale modifies the dynamics and condensate morphology. With end-pausing crosslinking motors, filaments self-organize into half asters and fully-symmetric asters under spherical confinement, polarity-sorted bilayers and bottle-brush-like states under cylindrical confinement, and flattened asters under planar confinement. The number of crosslinking motors controls the size and shape of condensates, with flattened asters becoming hollow and ring-like for larger motor number. End pausing plays a key role affecting condensate morphology: systems with end-pausing motors evolve into aster-like condensates while those with non-end-pausing crosslinking motor proteins evolve into disordered clusters and polarity-sorted bundles.
Language	English
Publishing date	2022-06-24
Publishing country	Switzerland
Document type	Journal Article
ZDB-ID	2721033-9
ISSN	2296-424X
ISSN	2296-424X
DOI	10.3389/fphy.2022.897255
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Article ; Online: Collective motion of driven semiflexible filaments tuned by soft repulsion and stiffness.

Moore, Jeffrey M / Thompson, Tyler N / Glaser, Matthew A / Betterton, Meredith D

Soft matter

2020 Volume 16, Issue 41, Page(s) 9436–9442

Abstract: In active matter systems, self-propelled particles can self-organize to undergo collective motion, leading to persistent dynamical behavior out of equilibrium. In cells, cytoskeletal filaments and motor proteins form complex structures important for cell ...

Abstract	In active matter systems, self-propelled particles can self-organize to undergo collective motion, leading to persistent dynamical behavior out of equilibrium. In cells, cytoskeletal filaments and motor proteins form complex structures important for cell mechanics, motility, and division. Collective dynamics of cytoskeletal systems can be reconstituted using filament gliding experiments, in which cytoskeletal filaments are propelled by surface-bound motor proteins. These experiments have observed diverse dynamical states, including flocks, polar streams, swirling vortices, and single-filament spirals. Recent experiments with microtubules and kinesin motor proteins found that the collective behavior of gliding filaments can be tuned by altering the concentration of the crowding macromolecule methylcellulose in solution. Increasing the methylcellulose concentration reduced filament crossing, promoted alignment, and led to a transition from active, isotropically oriented filaments to locally aligned polar streams. This emergence of collective motion is typically explained as an increase in alignment interactions by Vicsek-type models of active polar particles. However, it is not yet understood how steric interactions and bending stiffness modify the collective behavior of active semiflexible filaments. Here we use simulations of driven filaments with tunable soft repulsion and rigidity in order to better understand how the interplay between filament flexibility and steric effects can lead to different active dynamic states. We find that increasing filament stiffness decreases the probability of filament alignment, yet increases collective motion and long-range order, in contrast to the assumptions of a Vicsek-type model. We identify swirling flocks, polar streams, buckling bands, and spirals, and describe the physics that govern transitions between these states. In addition to repulsion and driving, tuning filament stiffness can promote collective behavior, and controls the transition between active isotropic filaments, locally aligned flocks, and polar streams.
MeSH term(s)	Cytoskeleton ; Kinesin ; Microtubules ; Motion ; Myosins
Chemical Substances	Myosins (EC 3.6.4.1) ; Kinesin (EC 3.6.4.4)
Language	English
Publishing date	2020-09-22
Publishing country	England
Document type	Journal Article
ZDB-ID	2191476-X
ISSN	1744-6848 ; 1744-683X
ISSN (online)	1744-6848
ISSN	1744-683X
DOI	10.1039/d0sm01036g
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Article ; Online: Polar in-plane surface orientation of a ferroelectric nematic liquid crystal: Polar monodomains and twisted state electro-optics.

Chen, Xi / Korblova, Eva / Glaser, Matthew A / Maclennan, Joseph E / Walba, David M / Clark, Noel A

Proceedings of the National Academy of Sciences of the United States of America

2021 Volume 118, Issue 22

Abstract: We show that surface interactions can vectorially structure the three-dimensional polarization field of a ferroelectric fluid. The contact between a ferroelectric nematic liquid crystal and a surface with in-plane polarity generates a preferred in-plane ... ...

Abstract	We show that surface interactions can vectorially structure the three-dimensional polarization field of a ferroelectric fluid. The contact between a ferroelectric nematic liquid crystal and a surface with in-plane polarity generates a preferred in-plane orientation of the polarization field at that interface. This is a route to the formation of fluid or glassy monodomains of high polarization without the need for electric field poling. For example, unidirectional buffing of polyimide films on planar surfaces to give quadrupolar in-plane anisotropy also induces macroscopic in-plane polar order at the surfaces, enabling the formation of a variety of azimuthal polar director structures in the cell interior, including uniform and twisted states. In a π-twist cell, obtained with antiparallel, unidirectional buffing on opposing surfaces, we demonstrate three distinct modes of ferroelectric nematic electro-optic response: intrinsic, viscosity-limited, field-induced molecular reorientation; field-induced motion of domain walls separating twisted states of opposite chirality; and propagation of polarization reorientation solitons from the cell plates to the cell center upon field reversal. Chirally doped ferroelectric nematics in antiparallel-rubbed cells produce Grandjean textures of helical twist that can be unwound via field-induced polar surface reorientation transitions. Fields required are in the 3-V/mm range, indicating an in-plane polar anchoring energy of
Language	English
Publishing date	2021-04-30
Publishing country	United States
Document type	Journal Article
ZDB-ID	209104-5
ISSN	1091-6490 ; 0027-8424
ISSN (online)	1091-6490
ISSN	0027-8424
DOI	10.1073/pnas.2104092118
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Article ; Online: Toward the cellular-scale simulation of motor-driven cytoskeletal assemblies.

Yan, Wen / Ansari, Saad / Lamson, Adam / Glaser, Matthew A / Blackwell, Robert / Betterton, Meredith D / Shelley, Michael

eLife

2022 Volume 11

Abstract: The cytoskeleton - a collection of polymeric filaments, molecular motors, and crosslinkers - is a foundational example of active matter, and in the cell assembles into organelles that guide basic biological functions. Simulation of cytoskeletal ... ...

Abstract	The cytoskeleton - a collection of polymeric filaments, molecular motors, and crosslinkers - is a foundational example of active matter, and in the cell assembles into organelles that guide basic biological functions. Simulation of cytoskeletal assemblies is an important tool for modeling cellular processes and understanding their surprising material properties. Here, we present
MeSH term(s)	Computer Simulation ; Cytoskeleton/metabolism ; Microtubules/metabolism ; Models, Biological ; Molecular Motor Proteins/metabolism
Chemical Substances	Molecular Motor Proteins
Language	English
Publishing date	2022-05-26
Publishing country	England
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	2687154-3
ISSN	2050-084X ; 2050-084X
ISSN (online)	2050-084X
ISSN	2050-084X
DOI	10.7554/eLife.74160
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Article ; Online: Theory of Cytoskeletal Reorganization during Cross-Linker-Mediated Mitotic Spindle Assembly.

Lamson, Adam R / Edelmaier, Christopher J / Glaser, Matthew A / Betterton, Meredith D

Biophysical journal

2019 Volume 116, Issue 9, Page(s) 1719–1731

Abstract: Cells grow, move, and respond to outside stimuli by large-scale cytoskeletal reorganization. A prototypical example of cytoskeletal remodeling is mitotic spindle assembly, during which microtubules nucleate, undergo dynamic instability, bundle, and ... ...

Abstract	Cells grow, move, and respond to outside stimuli by large-scale cytoskeletal reorganization. A prototypical example of cytoskeletal remodeling is mitotic spindle assembly, during which microtubules nucleate, undergo dynamic instability, bundle, and organize into a bipolar spindle. Key mechanisms of this process include regulated filament polymerization, cross-linking, and motor-protein activity. Remarkably, using passive cross-linkers, fission yeast can assemble a bipolar spindle in the absence of motor proteins. We develop a torque-balance model that describes this reorganization because of dynamic microtubule bundles, spindle-pole bodies, the nuclear envelope, and passive cross-linkers to predict spindle-assembly dynamics. We compare these results to those obtained with kinetic Monte Carlo-Brownian dynamics simulations, which include cross-linker-binding kinetics and other stochastic effects. Our results show that rapid cross-linker reorganization to microtubule overlaps facilitates cross-linker-driven spindle assembly, a testable prediction for future experiments. Combining these two modeling techniques, we illustrate a general method for studying cytoskeletal network reorganization.
MeSH term(s)	Biomechanical Phenomena ; Microtubules/metabolism ; Mitosis ; Models, Biological ; Monte Carlo Method ; Spindle Apparatus/metabolism ; Stochastic Processes
Language	English
Publishing date	2019-04-13
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, U.S. Gov't, Non-P.H.S.
ZDB-ID	218078-9
ISSN	1542-0086 ; 0006-3495
ISSN (online)	1542-0086
ISSN	0006-3495
DOI	10.1016/j.bpj.2019.03.013
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Article ; Online: The smectic Z

Chen, Xi / Martinez, Vikina / Korblova, Eva / Freychet, Guillaume / Zhernenkov, Mikhail / Glaser, Matthew A / Wang, Cheng / Zhu, Chenhui / Radzihovsky, Leo / Maclennan, Joseph E / Walba, David M / Clark, Noel A

Proceedings of the National Academy of Sciences of the United States of America

2023 Volume 120, Issue 8, Page(s) e2217150120

Abstract: We have structurally characterized the liquid crystal (LC) phase that can appear as an intermediate state when a dielectric nematic, having polar disorder of its molecular dipoles, transitions to the almost perfectly polar-ordered ferroelectric nematic. ... ...

Abstract	We have structurally characterized the liquid crystal (LC) phase that can appear as an intermediate state when a dielectric nematic, having polar disorder of its molecular dipoles, transitions to the almost perfectly polar-ordered ferroelectric nematic. This intermediate phase, which fills a 100-y-old void in the taxonomy of smectic LCs and which we term the "smectic Z
Language	English
Publishing date	2023-02-15
Publishing country	United States
Document type	Journal Article
ZDB-ID	209104-5
ISSN	1091-6490 ; 0027-8424
ISSN (online)	1091-6490
ISSN	0027-8424
DOI	10.1073/pnas.2217150120
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bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular
Jg. 1995 - 2021: Lesesall (1.OG)
ab Jg. 2022: Lesesaal (EG)

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Book ; Online: Thermotropic reentrant isotropy and antiferroelectricity in the ferroelectric nematic material RM734

Chen, Xi / Shuai, Min / Zhong, Bingchen / Martinez, Vikina / Korblova, Eva / Glaser, Matthew A. / Maclennan, Joseph E. / Walba, David M. / Clark, Noel A.

2023

Abstract: We report a transition from the ferroelectric nematic liquid crystal ($N_F$) phase to a lower-temperature, antiferroelectric fluid phase having reentrant isotropic symmetry ($I_A$), in the liquid crystal compound RM734 doped with small concentrations of ... ...

Abstract	We report a transition from the ferroelectric nematic liquid crystal ($N_F$) phase to a lower-temperature, antiferroelectric fluid phase having reentrant isotropic symmetry ($I_A$), in the liquid crystal compound RM734 doped with small concentrations of the ionic liquids BMIM or EMIM. Even a trace amount of ionic liquid dopant facilitates the kinetic pathway for the transition from the $N_F$ to the $I_A$, enabling simple cooling to produce this isotropic fluid phase rather than resulting in crystallization. The $I_A$ was also obtained in the absence of specific ionic liquid doping by appropriate temperature cycling in three distinct, as-synthesized-and-purified batches of RM734, two commercial and one from our laboratory. An additional birefringent, lamellar-modulated, antiferroelectric phase with the director parallel to the layers, resembling the smectic $Z_A$, is found between the paraelectric and ferroelectric nematic phases in RM734/BMIM mixtures. Comment: 45 pages, including Supplementary Information
Keywords	Condensed Matter - Soft Condensed Matter
Subject code	660
Publishing date	2023-09-10
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: Thermotropic reentrant isotropy and antiferroelectricity in the ferroelectric nematic realm

Zhong, Bingchen / Shuai, Min / Chen, Xi / Martinez, Vikina / Korblova, Eva / Glaser, Matthew A. / Maclennan, Joseph E. / Walba, David M. / Clark, Noel A.

Comparing RM734 and DIO

2023

Abstract: The current intense study of ferroelectric nematic liquid crystals was initiated by the observation of the same ferroelectric nematic phase in two independently discovered organic rod-shaped mesogenic compounds, RM734 and DIO. We recently reported that ... ...

Abstract	The current intense study of ferroelectric nematic liquid crystals was initiated by the observation of the same ferroelectric nematic phase in two independently discovered organic rod-shaped mesogenic compounds, RM734 and DIO. We recently reported that the compound RM734 also exhibits a monotropic, low-temperature, antiferroelectric phase having reentrant isotropic symmetry (the $I_A$ phase), the formation of which is facilitated to a remarkable degree by doping with small (below $1\%$) amounts of the ionic liquid ${\rm BMIM-PF}_6$. Here we report similar phenomenology in DIO, showing that this reentrant isotropic behavior is not only a property of RM734 but is rather a more general, material-independent feature of ferroelectric nematic mesogens. We find that the reentrant isotropic phases observed in RM734 and DIO are similar but not identical, adding two new phases to the ferroelectric nematic realm. The two $I_A$ phases exhibit similar, strongly peaked, diffuse x-ray scattering in the WAXS range $(1<q<2 \, \AA^{-1})$ indicative of a distinctive mode of short-ranged, side-by-side molecular packing. The scattering of the $I_A$ phases at small $q$ is quite different in the two materials, however, with RM734 exhibiting a strong, single, diffuse peak at $q \sim 0.08 \,\AA ^{-1}$ indicating mesoscale modulation with $\sim 80 \,\AA$ periodicity, and DIO a sharper diffuse peak at $q \sim 0.27 \,\AA ^{-1} \sim (2\pi/{\rm molecular length})$, with second and third harmonics, indicating that in the $I_A$ phase of DIO, short-ranged molecular positional correlation is smectic layer-like.<br /> Comment: main text 22 pages and 7 figures; supplement 9 pages and 6 figures. arXiv admin note: substantial text overlap with arXiv:2309.04935
Keywords	Condensed Matter - Soft Condensed Matter
Subject code	612
Publishing date	2023-12-28
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: Comparison of explicit and mean-field models of cytoskeletal filaments with crosslinking motors.

Lamson, Adam R / Moore, Jeffrey M / Fang, Fang / Glaser, Matthew A / Shelley, Michael J / Betterton, Meredith D

The European physical journal. E, Soft matter

2021 Volume 44, Issue 3, Page(s) 45

Abstract: In cells, cytoskeletal filament networks are responsible for cell movement, growth, and division. Filaments in the cytoskeleton are driven and organized by crosslinking molecular motors. In reconstituted cytoskeletal systems, motor activity is ... ...

Abstract	In cells, cytoskeletal filament networks are responsible for cell movement, growth, and division. Filaments in the cytoskeleton are driven and organized by crosslinking molecular motors. In reconstituted cytoskeletal systems, motor activity is responsible for far-from-equilibrium phenomena such as active stress, self-organized flow, and spontaneous nematic defect generation. How microscopic interactions between motors and filaments lead to larger-scale dynamics remains incompletely understood. To build from motor-filament interactions to predict bulk behavior of cytoskeletal systems, more computationally efficient techniques for modeling motor-filament interactions are needed. Here, we derive a coarse-graining hierarchy of explicit and continuum models for crosslinking motors that bind to and walk on filament pairs. We compare the steady-state motor distribution and motor-induced filament motion for the different models and analyze their computational cost. All three models agree well in the limit of fast motor binding kinetics. Evolving a truncated moment expansion of motor density speeds the computation by [Formula: see text]-[Formula: see text] compared to the explicit or continuous-density simulations, suggesting an approach for more efficient simulation of large networks. These tools facilitate further study of motor-filament networks on micrometer to millimeter length scales.
MeSH term(s)	Cytoskeleton/metabolism ; Kinetics ; Microtubules/metabolism ; Models, Biological ; Molecular Motor Proteins/metabolism
Chemical Substances	Molecular Motor Proteins
Language	English
Publishing date	2021-03-29
Publishing country	France
Document type	Journal Article
ZDB-ID	2004003-9
ISSN	1292-895X ; 1292-8941
ISSN (online)	1292-895X
ISSN	1292-8941
DOI	10.1140/epje/s10189-021-00042-9
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