scholarly journals A model for the self-organization of microtubules driven by molecular motors

2000 ◽  
Vol 15 (3) ◽  
pp. 483-492 ◽  
Author(s):  
B. Bassetti ◽  
M. Cosentino Lagomarsino ◽  
P. Jona
Keyword(s):  
Molecular Motors ◽  
The Self ◽  
Self Organization

scholarly journals A gelation transition enables the self-organization of bipolar metaphase spindles

2021 ◽  
Author(s):  
Benjamin A. Dalton ◽  
David Oriola ◽  
Franziska Decker ◽  
Frank Jülicher ◽  
Jan Brugués
Keyword(s):  
Molecular Motors ◽  
Mitotic Spindle ◽  
Large Scale ◽  
Relaxation Times ◽  
Network Connectivity ◽  
The Self ◽  
Self Organization ◽  
Bipolar Structure ◽  
Microtubule Polarity ◽  
Microtubule Transport

The mitotic spindle is a highly dynamic bipolar structure that emerges from the self-organization of microtubules, molecular motors, and other proteins. Sustained motor-driven poleward flows of short dynamic microtubules play a key role in the bipolar organization of spindles. However, it is not understood how the local activity of motor proteins generates these large-scale coherent poleward flows. Here, we combine experiments and simulations to show that a gelation transition enables long-ranged microtubule transport causing spindles to self-organize into two oppositely polarized microtubule gels. Laser ablation experiments reveal that local active stresses generated at the spindle midplane propagate through the structure thereby driving global coherent microtubule flows. Simulations show that microtubule gels undergoing rapid turnover can exhibit long stress relaxation times, in agreement with the long-ranged flows observed in experiments. Finally, we show that either disrupting such flows or decreasing the network connectivity can lead to a microtubule polarity reversal in spindles both in the simulations and in the experiments. Thus, we uncover an unexpected connection between spindle rheology and architecture in spindle self-organization.

scholarly journals Filament Rigidity and Connectivity Tune the Deformation Modes of Active Biopolymer Networks

2017 ◽  
Author(s):  
Samantha Stam ◽  
Simon L. Freedman ◽  
Shiladitya Banerjee ◽  
Kimberly L. Weirich ◽  
Aaron R. Dinner ◽  
...  
Keyword(s):  
Molecular Motors ◽  
The Self ◽  
Self Organization ◽  
Cross Linking ◽  
Physical Parameters ◽  
Active Materials ◽  
Wide Range ◽  
Filament Bundles ◽  
Deformation Modes ◽  
Insight Into

ABSTRACTMolecular motors embedded within collections of actin and microtubule filaments underlie the dynamic behaviors of cytoskeletal assemblies. Understanding the physics of such motor-filament materials is critical to developing a physical model of the cytoskeleton and the design of biomimetic active materials. Here, we demonstrate through experiments and simulations that the rigidity and connectivity of filaments in active biopolymer networks regulates the anisotropy and the length scale of the underlying deformations, yielding materials with varying contractility. Semi-flexible filaments that can be compressed and bent by motor stresses undergo deformations that are predominantly biaxial. By contrast, rigid filament bundles contract via actomyosin sliding deformations that are predominantly uniaxial. Networks dominated by filament buckling are robustly contractile under a wide range of connectivities, while networks dominated by actomyosin sliding can be tuned from contractile to extensile through reduced connectivity via cross-linking. These results identify physical parameters that control the forces generated within motor-filament arrays, and provide insight into the self-organization and mechanics of cytoskeletal assemblies.

scholarly journals Filament rigidity and connectivity tune the deformation modes of active biopolymer networks

2017 ◽  
Vol 114 (47) ◽  
pp. E10037-E10045 ◽  
Author(s):  
Samantha Stam ◽  
Simon L. Freedman ◽  
Shiladitya Banerjee ◽  
Kimberly L. Weirich ◽  
Aaron R. Dinner ◽  
...  
Keyword(s):  
Molecular Motors ◽  
The Self ◽  
Self Organization ◽  
Cross Linking ◽  
Physical Parameters ◽  
Active Materials ◽  
Wide Range ◽  
Filament Bundles ◽  
Deformation Modes ◽  
Insight Into

Molecular motors embedded within collections of actin and microtubule filaments underlie the dynamics of cytoskeletal assemblies. Understanding the physics of such motor-filament materials is critical to developing a physical model of the cytoskeleton and designing biomimetic active materials. Here, we demonstrate through experiments and simulations that the rigidity and connectivity of filaments in active biopolymer networks regulates the anisotropy and the length scale of the underlying deformations, yielding materials with variable contractility. We find that semiflexible filaments can be compressed and bent by motor stresses, yielding materials that undergo predominantly biaxial deformations. By contrast, rigid filament bundles slide without bending under motor stress, yielding materials that undergo predominantly uniaxial deformations. Networks dominated by biaxial deformations are robustly contractile over a wide range of connectivities, while networks dominated by uniaxial deformations can be tuned from extensile to contractile through cross-linking. These results identify physical parameters that control the forces generated within motor-filament arrays and provide insight into the self-organization and mechanics of cytoskeletal assemblies.

scholarly journals Influence of Salt on the Self-Organization in Solutions of Star-Shaped Poly-2-alkyl-2-oxazoline and Poly-2-alkyl-2-oxazine on Heating

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1152
Author(s):  
Tatyana Kirila ◽  
Anna Smirnova ◽  
Alla Razina ◽  
Andrey Tenkovtsev ◽  
Alexander Filippov
Keyword(s):  
Phase Separation ◽  
Salt Concentration ◽  
Monomer Unit ◽  
Salt Content ◽  
The Self ◽  
Self Organization ◽  
Phase Separation Temperature ◽  
The Core ◽  
Separation Temperature ◽  
Water Salt

The water–salt solutions of star-shaped six-arm poly-2-alkyl-2-oxazines and poly-2-alkyl-2-oxazolines were studied by light scattering and turbidimetry. The core was hexaaza[26]orthoparacyclophane and the arms were poly-2-ethyl-2-oxazine, poly-2-isopropyl-2-oxazine, poly-2-ethyl-2-oxazoline, and poly-2-isopropyl-2-oxazoline. NaCl and N-methylpyridinium p-toluenesulfonate were used as salts. Their concentration varied from 0–0.154 M. On heating, a phase transition was observed in all studied solutions. It was found that the effect of salt on the thermosensitivity of the investigated stars depends on the structure of the salt and polymer and on the salt content in the solution. The phase separation temperature decreased with an increase in the hydrophobicity of the polymers, which is caused by both a growth of the side radical size and an elongation of the monomer unit. For NaCl solutions, the phase separation temperature monotonically decreased with growth of salt concentration. In solutions with methylpyridinium p-toluenesulfonate, the dependence of the phase separation temperature on the salt concentration was non-monotonic with minimum at salt concentration corresponding to one salt molecule per one arm of a polymer star. Poly-2-alkyl-2-oxazine and poly-2-alkyl-2-oxazoline stars with a hexaaza[26]orthoparacyclophane core are more sensitive to the presence of salt in solution than the similar stars with a calix[n]arene branching center.

scholarly journals Modification of Mechanical Properties of High-Strength Titanium Alloys VT23 and VT23M Due to Impact-Oscillatory Loading

Metals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 80 ◽  
Author(s):  
Mykola Chausov ◽  
Janette Brezinová ◽  
Andrii Pylypenko ◽  
Pavlo Maruschak ◽  
Liudmyla Titova ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Titanium Alloys ◽  
High Strength ◽  
The Self ◽  
Self Organization ◽  
Two Phase ◽  
Rolled Metal ◽  
Technological Method ◽  
Equilibrium Processes ◽  
Production Conditions

A simple technological method is proposed and tested experimentally, which allows for the improvement of mechanical properties in sheet two-phase high-strength titanium alloys VT23 and VT23M on the finished product (rolled metal), due to impact-oscillatory loading. Under impact-oscillatory loading and dynamic non-equilibrium processes (DNP) are realized in titanium alloys, leading to the self-organization of the structure. As a result, the mechanical properties of titanium alloys vary significantly with subsequent loading after the realization of DNP. In this study, the test modes are found, which can be used in the production conditions.

scholarly journals Ferro-self-assembly: magnetic and electrochemical adaptation of a multiresponsive zwitterionic metalloamphiphile showing a shape-hysteresis effect

2021 ◽  
Vol 12 (1) ◽  
pp. 270-281
Author(s):  
Stefan Bitter ◽  
Moritz Schlötter ◽  
Markus Schilling ◽  
Marina Krumova ◽  
Sebastian Polarz ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Light Scattering ◽  
Dynamic Light Scattering ◽  
Real Time ◽  
Self Assembly ◽  
Hysteresis Effect ◽  
The Self ◽  
Self Organization ◽  
Stimuli Responsive ◽  
Optical Birefringence

The self-organization properties of a stimuli responsive amphiphile can be altered by subjecting the paramagnetic oxidized form to a magnetic field of 0.8 T and monitored in real time by coupling optical birefringence with dynamic light scattering.

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