scholarly journals Clustering and phase separation of circle swimmers dispersed in a monolayer

Soft Matter ◽  
2018 ◽  
Vol 14 (38) ◽  
pp. 7873-7882 ◽  
Author(s):  
Guo-Jun Liao ◽  
Sabine H. L. Klapp
Keyword(s):  
Phase Separation ◽  
Brownian Particles ◽  
Freely Moving ◽  
The Impact

Active Brownian particles can exhibit motility-induced phase separation, in which densely packed clusters coexist with freely moving swimmers. We investigate the impact of active rotation on the coexisting densities and discover a novel state of clockwise vortices.

scholarly journals Mechanical frustration of phase separation in the cell nucleus by chromatin

2020 ◽  
Author(s):  
Yaojun Zhang ◽  
Daniel S.W. Lee ◽  
Yigal Meir ◽  
Clifford P. Brangwynne ◽  
Ned S. Wingreen
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Cell Nucleus ◽  
Mechanical Environment ◽  
Coarsening Dynamics ◽  
The Impact ◽  
Droplet Phase ◽  
Liquid Liquid Phase Separation ◽  
Fundamental Mechanism

Liquid-liquid phase separation is a fundamental mechanism underlying subcellular organization. Motivated by the striking observation that optogenetically-generated droplets in the nucleus display suppressed coarsening dynamics, we study the impact of chromatin mechanics on droplet phase separation. We combine theory and simulation to show that crosslinked chromatin can mechanically suppress droplets’ coalescence and ripening, as well as quantitatively control their number, size, and placement. Our results highlight the role of the subcellular mechanical environment on condensate regulation.

scholarly journals Prebiotically-relevant low polyion multivalency can improve functionality of membraneless compartments

2020 ◽  
Author(s):  
Fatma Pir Cakmak ◽  
Saehyun Choi ◽  
McCauley O. Meyer ◽  
Philip C. Bevilacqua ◽  
Christine D. Keating
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Structure Formation ◽  
Rna Structure ◽  
Salt Resistance ◽  
Origins Of Life ◽  
Complex Coacervation ◽  
The Impact ◽  
Local Ph

AbstractMultivalent polyions can undergo complex coacervation, producing membraneless compartments that accumulate ribozymes and enhance catalysis, and offering a mechanism for functional prebiotic compartmentalization in the origins of life. Here, we evaluated the impact of low, prebiotically-relevant polyion multivalency in coacervate performance as functional compartments. As model polyions, we used positively and negatively charged homopeptides with one to 100 residues, and adenosine mono-, di-, and triphosphate nucleotides. Polycation/polyanion pairs were tested for coacervation, and resulting membraneless compartments were analyzed for salt resistance, ability to provide a distinct internal microenvironment (apparent local pH, RNA partitioning), and effect on RNA structure formation. We find that coacervates formed by phase separation of the relatively shorter polyions more effectively generated distinct pH microenvironments, accumulated RNA, and preserved duplexes. Hence, reduced multivalency polyions are not only viable as functional compartments for prebiotic chemistries, but they can offer advantages over higher molecular weight analogues.

A simple simulation model for complex coacervates

Soft Matter ◽  
2021 ◽  
Author(s):  
Sai Vineeth Bobbili ◽  
Scott Milner
Keyword(s):  
Phase Diagram ◽  
Aqueous Solution ◽  
Phase Separation ◽  
Simulation Model ◽  
Simple Simulation ◽  
The Impact ◽  
Oppositely Charged

When oppositely charged polyelectrolytes mix in an aqueous solution, associative phase separation gives rise to coacervates. Experiments reveal the phase diagram for such coacervates, and determine the impact of charge...

scholarly journals Prebiotically-relevant low polyion multivalency can improve functionality of membraneless compartments

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Fatma Pir Cakmak ◽  
Saehyun Choi ◽  
McCauley O. Meyer ◽  
Philip C. Bevilacqua ◽  
Christine D. Keating
Keyword(s):  
Molecular Weight ◽  
Phase Separation ◽  
Structure Formation ◽  
Rna Structure ◽  
Functional Performance ◽  
Salt Resistance ◽  
Origins Of Life ◽  
Complex Coacervation ◽  
The Impact ◽  
Local Ph

AbstractMultivalent polyions can undergo complex coacervation, producing membraneless compartments that accumulate ribozymes and enhance catalysis, and offering a mechanism for functional prebiotic compartmentalization in the origins of life. Here, we evaluate the impact of lower, more prebiotically-relevant, polyion multivalency on the functional performance of coacervates as compartments. Positively and negatively charged homopeptides with 1–100 residues and adenosine mono-, di-, and triphosphate nucleotides are used as model polyions. Polycation/polyanion pairs are tested for coacervation, and resulting membraneless compartments are analyzed for salt resistance, ability to provide a distinct internal microenvironment (apparent local pH, RNA partitioning), and effect on RNA structure formation. We find that coacervates formed by phase separation of the shorter polyions more effectively generated distinct pH microenvironments, accumulated RNA, and preserved duplexes than those formed by longer polyions. Hence, coacervates formed by reduced multivalency polyions are not only viable as functional compartments for prebiotic chemistries, they can outperform higher molecular weight analogues.

scholarly journals The evolution of ultra-massive white dwarfs

2019 ◽  
Vol 625 ◽  
pp. A87 ◽  
Author(s):  
María E. Camisassa ◽  
Leandro G. Althaus ◽  
Alejandro H. Córsico ◽  
Francisco C. De Gerónimo ◽  
Marcelo M. Miller Bertolami ◽  
...  
Keyword(s):  
Phase Separation ◽  
White Dwarf ◽  
White Dwarfs ◽  
Outer Boundary ◽  
Asymptotic Giant Branch ◽  
Type Ia ◽  
Chemical Profiles ◽  
Supernova Explosions ◽  
Carbon Burning ◽  
The Impact

Ultra-massive white dwarfs are powerful tools used to study various physical processes in the asymptotic giant branch (AGB), type Ia supernova explosions, and the theory of crystallization through white dwarf asteroseismology. Despite the interest in these white dwarfs, there are few evolutionary studies in the literature devoted to them. Here we present new ultra-massive white dwarf evolutionary sequences that constitute an improvement over previous ones. In these new sequences we take into account for the first time the process of phase separation expected during the crystallization stage of these white dwarfs by relying on the most up-to-date phase diagram of dense oxygen/neon mixtures. Realistic chemical profiles resulting from the full computation of progenitor evolution during the semidegenerate carbon burning along the super-AGB phase are also considered in our sequences. Outer boundary conditions for our evolving models are provided by detailed non-gray white dwarf model atmospheres for hydrogen and helium composition. We assessed the impact of all these improvements on the evolutionary properties of ultra-massive white dwarfs, providing updated evolutionary sequences for these stars. We conclude that crystallization is expected to affect the majority of the massive white dwarfs observed with effective temperatures below 40 000 K. Moreover, the calculation of the phase separation process induced by crystallization is necessary to accurately determine the cooling age and the mass-radius relation of massive white dwarfs. We also provide colors in the Gaia photometric bands for our H-rich white dwarf evolutionary sequences on the basis of new model atmospheres. Finally, these new white dwarf sequences provide a new theoretical frame to perform asteroseismological studies on the recently detected ultra-massive pulsating white dwarfs.

scholarly journals Liquid–Liquid Phase Separation in Crowded Environments

2020 ◽  
Vol 21 (16) ◽  
pp. 5908 ◽  
Author(s):  
Alain A. M. André ◽  
Evan Spruijt
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Macromolecular Crowding ◽  
Liquid Phase Separation ◽  
The Impact ◽  
Crowded Environments ◽  
Liquid Liquid Phase Separation ◽  
In Cells

Biomolecular condensates play a key role in organizing cellular fluids such as the cytoplasm and nucleoplasm. Most of these non-membranous organelles show liquid-like properties both in cells and when studied in vitro through liquid–liquid phase separation (LLPS) of purified proteins. In general, LLPS of proteins is known to be sensitive to variations in pH, temperature and ionic strength, but the role of crowding remains underappreciated. Several decades of research have shown that macromolecular crowding can have profound effects on protein interactions, folding and aggregation, and it must, by extension, also impact LLPS. However, the precise role of crowding in LLPS is far from trivial, as most condensate components have a disordered nature and exhibit multiple weak attractive interactions. Here, we discuss which factors determine the scope of LLPS in crowded environments, and we review the evidence for the impact of macromolecular crowding on phase boundaries, partitioning behavior and condensate properties. Based on a comparison of both in vivo and in vitro LLPS studies, we propose that phase separation in cells does not solely rely on attractive interactions, but shows important similarities to segregative phase separation.

scholarly journals Effect of TiO2 Powder on the Surface Morphology of Micro/Nanoporous Structured Hydrophobic Fluoropolymer Based Composite Material

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
Bichitra Nanda Sahoo ◽  
Balasubramanian Kandasubramanian ◽  
Amrutha Thomas
Keyword(s):  
Phase Separation ◽  
Surface Morphology ◽  
Polymer Composite ◽  
Polyvinylidene Fluoride ◽  
Industrial Applications ◽  
Nanoporous Structure ◽  
Hydrophobic Surfaces ◽  
Water Contact ◽  
Maximum Water ◽  
The Impact

The present work reports a simple and effective way to produce hydrophobic foams with polyvinylidene fluoride (PVDF) and TiO2 by using a phase separation technique. This method involved the phase separation during the deposition of PVDF from its DMF solution with nonsolvent water in the presence of TiO2. The surface morphology of hydrophobic surfaces was characterized by Field Emission Scanning Electron Microscope (FESEM). The maximum water contact angle of 129° was observed. The results confirm that the surface texture of polymer composite exhibits mixture of microporous and nanoporous structure. The impact of TiO2 on the wettability property of polymer composite has been studied. The proposed methodology might find applications in the preparation of hydrophobic surfaces for industrial applications.

scholarly journals Local thermodynamics governs the formation and dissolution of protein condensates in living cells

2021 ◽  
Author(s):  
Anatol W. Fritsch ◽  
Andrés F. Diaz-Delgadillo ◽  
Omar Adame-Arana ◽  
Carsten Hoege ◽  
Matthäus Mittasch ◽  
...  
Keyword(s):  
Phase Separation ◽  
Thermodynamic Equilibrium ◽  
Spatial Organization ◽  
Living Cells ◽  
Fast Diffusion ◽  
Temperature Changes ◽  
P Granules ◽  
Active Processes ◽  
Molecular Components ◽  
The Impact

Membraneless compartments, also known as condensates, provide chemically distinct environments and thus spatially organize the cell. A well-studied example of condensates is P granules in the roundworm C. elegans which play an important role in the development of the germline. P granules are RNA-rich protein condensates that share the key properties of liquid droplets such as a spherical shape, the ability to fuse, and fast diffusion of their molecular components. An outstanding question is to what extent phase separation at thermodynamic equilibrium is appropriate to describe the formation of condensates in an active cellular environment. To address this question, we investigate the response of P granule condensates in living cells to temperature changes. We observe that P granules dissolve upon increasing the temperature and recondense upon lowering the temperature in a reversible manner. Strikingly, this temperature response can be captured by in vivo phase diagrams which are well described by a Flory-Huggins model at thermodynamic equilibrium. This finding is surprising due to active processes in a living cell. To address the impact of such active processes on intra-cellular phase separation, we discuss temperature heterogeneities. We show that, for typical estimates of the density of active processes, temperature represents a well-defined variable and that mesoscopic volume elements are at local thermodynamic equilibrium. Our findings provide strong evidence that P granule assembly and disassembly are governed by phase separation based on local thermal equilibria where the non-equilibrium nature of the cytoplasm is manifested on larger scales.SIGNIFICANCE STATEMENTLiving cells rely on a continuous flux of energy to spatially organize biochemical processes. It remained unclear whether cells can achieve this spatial organization via thermodynamic principles. Here, we report the striking behavior of a cold-blooded organism that reacts to environmental temperature changes similar to a thermodynamic system at local equilibrium. Our key finding is that protein-rich droplets form and dissolve reversibly with temperature due to changes in the organism?s entropy. We show that the organism uses a specific molecule to extend droplet stability to the natural temperature range of the organism’s habitat. Due to the relevance of such protein droplets for the organism?s fertility, our works shed light on how molecular components could facilitate biological functions via thermodynamic principles.

scholarly journals Continuum modelling of structure formation of biosilica patterns in diatoms

BMC Materials ◽  
2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Manfred Bobeth ◽  
Arezoo Dianat ◽  
Rafael Gutierrez ◽  
David Werner ◽  
Hongliu Yang ◽  
...  
Keyword(s):  
Phase Separation ◽  
Pattern Formation ◽  
Structure Formation ◽  
Organic Molecules ◽  
Experimental Studies ◽  
Formation Mechanisms ◽  
Phosphate Ions ◽  
High Regularity ◽  
The Impact

Abstract Formation of regularly structured silica valves of various diatom species is a particularly fascinating phenomenon in biomineralization. Intensive investigations have been devoted to elucidate the formation mechanisms of diatom valve structures. Phase-separation of species-specific organic molecules has been proposed to be involved in pattern formation, where the evolving organic molecule structures serve as template for silica formation. In the present work, using a continuum approach, we investigate the conditions under which silica structures of high regularity can develop within a phase separation model. In relation to previously reported in vitro experiments of silica formation, which revealed the important role of phosphate ions in the self-assembly of organic molecules, we propose a model where phase separation is coupled with a chemical reaction. We analyze the impact of the reaction of phosphate ions with organic molecules on the appearing morphology of the organic template. Two- and three-dimensional simulations of the development of regular stationary patterns are presented. The influence of a confined geometry and an interaction of organic molecules with the walls on pattern formation is also addressed. We expect that our approach will be relevant for experimental studies aiming at inducing structure formation under controlled in vitro conditions.

Sign in / Sign up

Export Citation Format

Share Document