scholarly journals More than just oil droplets in water: surface tension and viscosity of protein condensates quantified by micropipette aspiration

2021 ◽  
Author(s):  
Huan Wang ◽  
Fleurie M Kelley ◽  
Dragomir Milovanovic ◽  
Benjamin S Schuster ◽  
Zheng Shi
Keyword(s):  
Surface Tension ◽  
Phase Separation ◽  
Liquid Phase ◽  
Material Properties ◽  
Water Surface ◽  
Phase System ◽  
Surface Wetting ◽  
Two Phase ◽  
Quantitative Studies ◽  
Liquid Liquid Phase Separation

The material properties of biomolecular condensates play pivotal roles in many biological and pathological processes. Despite the rapid increase in the number of biomolecules identified that undergo liquid-liquid phase separation (LLPS), quantitative studies of the resulting condensates have been severely lagging behind. Here, we develop a micropipette-based technique, which uniquely allows quantifications of both the surface tension and viscosity of biomolecular condensates, independent of labeling and surface wetting effects. We demonstrate the accuracy and versatility of this technique by measuring condensates of LAF-1 RGG domains and a polymer-based aqueous two-phase system (ATPS). We anticipate this technique will be widely applicable to biomolecular condensates and will resolve several limitations regarding current approaches.

scholarly journals Concentric annular liquid–liquid phase separation for flow chemistry and continuous processing

2021 ◽  
Author(s):  
Matthew J. Harding ◽  
Bin Feng ◽  
Rafael Lopez-Rodriguez ◽  
Heather O'Connor ◽  
Denis Dowling ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Low Cost ◽  
Flow Chemistry ◽  
Continuous Processing ◽  
Surface Wetting ◽  
Tubular Membrane ◽  
Annular Channels ◽  
Phase Separator ◽  
Liquid Liquid Phase Separation

A low-cost, modular, robust, and easily customisable continuous liquid–liquid phase separator has been developed that uses a tubular membrane and annular channels to allow high fluidic throughputs while maintaining rapid, surface wetting dominated, phase separation.

scholarly journals Surface electrostatics govern the emulsion stability of biomolecular condensates

2020 ◽  
Author(s):  
Timothy J. Welsh ◽  
Georg Krainer ◽  
Jorge R. Espinosa ◽  
Jerelle A. Joseph ◽  
Akshay Sridhar ◽  
...  
Keyword(s):  
Surface Tension ◽  
Phase Separation ◽  
Liquid Phase ◽  
Zeta Potential ◽  
Molecular Modelling ◽  
Emulsion Stability ◽  
Zeta Potentials ◽  
Molecular Determinants ◽  
Repulsive Forces ◽  
Liquid Liquid Phase Separation

AbstractLiquid–liquid phase separation underlies the formation of biological condensates. Physically, such systems are microemulsions which have a general propensity to fuse and coalesce; however, many condensates persist as independent droplets inside cells. This stability is crucial for their functioning, but the physicochemical mechanisms that control the emulsion stability of condensates remain poorly understood. Here, by combining single-condensate zeta potential measurements, optical microscopy, tweezer experiments, and multiscale molecular modelling, we investigate how the forces that sustain condensates impact their stability against fusion. By comparing PR25:PolyU and FUS condensates, we show that a higher condensate surface charge correlates with a lower fusion propensity, and that this behavior can be inferred from their zeta potentials. We reveal that overall stabilization against fusion stems from a combination of repulsive forces between condensates and the effects that surface electrostatics have on lowering surface tension, thus shedding light on the molecular determinants of condensate coalescence.

scholarly journals Valency and Binding Affinity Variations Can Regulate the Multilayered Organization of Protein Condensates with Many Components

Biomolecules ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 278
Author(s):  
Ignacio Sanchez-Burgos ◽  
Jorge R. Espinosa ◽  
Jerelle A. Joseph ◽  
Rosana Collepardo-Guevara
Keyword(s):  
Surface Tension ◽  
Phase Separation ◽  
Liquid Phase ◽  
Binding Affinity ◽  
Multilayered Structure ◽  
Scaffold Proteins ◽  
Coarse Grained ◽  
Binding Affinities ◽  
Coarse Grained Model ◽  
Liquid Liquid Phase Separation

Biomolecular condensates, which assemble via the process of liquid–liquid phase separation (LLPS), are multicomponent compartments found ubiquitously inside cells. Experiments and simulations have shown that biomolecular condensates with many components can exhibit multilayered organizations. Using a minimal coarse-grained model for interacting multivalent proteins, we investigate the thermodynamic parameters governing the formation of multilayered condensates through changes in protein valency and binding affinity. We focus on multicomponent condensates formed by scaffold proteins (high-valency proteins that can phase separate on their own via homotypic interactions) and clients (proteins recruited to condensates via heterotypic scaffold–client interactions). We demonstrate that higher valency species are sequestered to the center of the multicomponent condensates, while lower valency proteins cluster towards the condensate interface. Such multilayered condensate architecture maximizes the density of LLPS-stabilizing molecular interactions, while simultaneously reducing the surface tension of the condensates. In addition, multilayered condensates exhibit rapid exchanges of low valency proteins in and out, while keeping higher valency proteins—the key biomolecules involved in condensate nucleation—mostly within. We also demonstrate how modulating the binding affinities among the different proteins in a multicomponent condensate can significantly transform its multilayered structure, and even trigger fission of a condensate into multiple droplets with different compositions.

scholarly journals Thermodynamics of droplets undergoing liquid-liquid phase separation

2021 ◽  
Author(s):  
Subhadip Biswas ◽  
Biswaroop Mukherjee ◽  
Buddhapriya Chakrabarti
Keyword(s):  
Surface Tension ◽  
Phase Separation ◽  
Liquid Phase ◽  
Volume Fraction ◽  
Mean Field Theory ◽  
Equilibrium Phase ◽  
Mean Field ◽  
Liquid Phase Separation ◽  
Polymer Mixture ◽  
Liquid Liquid Phase Separation

We study the thermodynamics of binary mixtures wherein the volume fraction of the minority component is less than the amount required to form a flat interface. Based on an explicit microscopic mean field theory, we show that the surface tension dominated equilibrium phase of a polymer mixture forms a single macroscopic droplet. A combination of elastic interactions that renormalize the surface tension, and arrests phase separation for a gel-polymer mixture, stabilize a micro-droplet phase. We compute the droplet size as a function of the interfacial tension, Flory parameter, and elastic moduli of the gel. Our results illustrate the importance of the rheological properties of the solvent in dictating the thermodynamic phase behavior of biopolymers undergoing liquid-liquid phase separation.

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