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The phase separation of protein and RNA mixtures underpins the assembly and regulation of numerous membraneless organelles in cells. The ubiquity of protein–RNA condensates in cellular regulatory processes is in part due to their sensitivity to RNA concentration, which affects their physical properties and stability. Recent experiments with poly-cationic peptide–RNA mixtures have revealed closed-loop phase diagrams featuring lower and upper critical solution temperatures. These diagrams indicate reentrant phase transitions shaped by biomolecular interactions and entropic forces such as solvent and ion reorganization. We employed atomistic simulations to study mixtures with various RNA–polylysine stoichiometries and temperatures to elucidate the microscopic driving forces behind reentrant phase transitions in protein–RNA mixtures. Our findings reveal an intricate interplay between hydration, ion condensation, and specific RNA–polylysine hydrogen bonding, resulting in distinct stoichiometry-dependent phase equilibria governing stabilities and structures of the condensate phase. Our simulations show that reentrant transitions are accompanied by desolvation around the phosphate groups of RNA, with increased contacts between phosphate and lysine side chains. In RNA-rich systems at lower temperatures, RNA molecules can form an extensive pi-stacking and hydrogen bond network, leading to percolation. In protein-rich systems, no such percolation-induced transitions are observed. Furthermore, we assessed the performance of three prominent water force fields—Optimal Point Charge (OPC), TIP4P-2005, and TIP4P-D—in capturing reentrant phase transitions. OPC provided a superior balance of interactions, enabling effective capture of reentrant transitions and accurate characterization of changes in solvent reorganization. This study offers atomistic insights into the nature of reentrant phase transitions using simple model peptide and nucleotide mixtures. We believe that our results are broadly applicable to larger classes of peptide–RNA mixtures exhibiting reentrant phase transitions. [ABSTRACT FROM AUTHOR]

AbstractStar-shaped six-arm polymers with arms of the block copolymers of poly-2-ethyl-2-oxazine and poly-2-isopropyl-2-oxazine were synthesized. The branching center was hexaase[26]cyclophane. The prepared samples differed in the order of block attachment to the core. Molar masses of the two samples were 14200 and 21500 g⋅mol−1. The fractions of poly-2-ethyl-2-oxazine monomers in the arms were 61 and 65%, respectively. It was shown that the arms were strongly folded. Water-salt solutions of the star-shaped block copolymers exhibited thermoresponsiveness. The difference in the phase separation temperatures for the studied samples was caused by the differences in their molar masses and the different contents of poly-2-ethyl- and poly-2-isopropyl-2-oxazine blocks. The concentration dependences of the phase separation temperatures for the synthesized star-shaped copolymers coincided with those for the arms, despite the fact that the molecular masses of the stars and their arms differed by factor of near 6. The addition of NaCl to the aqueous of solutions of the star copolymers did not lead to significant changes in their characteristics. No influence of the order of the block attachment to the core on the molecule conformation and on the thermoresponsive behavior was found. [ABSTRACT FROM AUTHOR]

Protein phase transitions (PPTs) from the soluble state to a dense liquid phase (forming droplets via liquid-liquid phase separation) or to solid aggregates (such as amyloids) play key roles in pathological processes associated with age-related diseases such as Alzheimer's disease. Several computational frameworks are capable of separately predicting the formation of droplets or amyloid aggregates based on protein sequences, yet none have tackled the prediction of both within a unified framework. Recently, large language models (LLMs) have exhibited great success in protein structure prediction; however, they have not yet been used for PPTs. Here, we fine-tune a LLM for predicting PPTs and demonstrate its usage in evaluating how sequence variants affect PPTs, an operation useful for protein design. In addition, we show its superior performance compared to suitable classical benchmarks. Due to the "black-box" nature of the LLM, we also employ a classical random forest model along with biophysical features to facilitate interpretation. Finally, focusing on Alzheimer's disease-related proteins, we demonstrate that greater aggregation is associated with reduced gene expression in Alzheimer's disease, suggesting a natural defense mechanism. [ABSTRACT FROM AUTHOR]

This study reports the reversible solubility switching of a polymer triggered by non‐phototoxic visible light. A photochromic polymerizable azobenzene monomer with four methoxy groups at the ortho‐position (mAzoA) was synthesized, exhibiting reversible photoisomerization between trans‐ and cis‐states using green (546 nm) and blue light (436 nm). Free radical copolymerization of hydrophilic dimethylacrylamide (DMAAm) with mAzoA produced a light‐responsive random copolymer (P(mAzoA‐r‐DMAAm)) that shows a reversible photochromic reaction to visible light. Optimizing mAzoA content resulted in P(mAzoA10.7‐r‐DMAAm)3.0 kDa exhibiting LCST‐type phase separation in PBS (pH 7.4) with trans‐ and cis‐states at 39.2 °C and 32.9 °C, respectively. The bistable temperature range of 6.3 °C covers 37 °C, suitable for mammalian cell culture. Reversible solubility changes were demonstrated under alternating green and blue light at 37 °C. 1H NMR indicated significant retardation of thermal relaxation from cis‐ to trans‐states, preventing undesired thermal mechanical degradation. Madin Darby Canine Kidney (MDCK) cells adhered to the P(mAzoA‐r‐DMAAm) hydrogel, confirming its non‐cytotoxicity and potential for biocompatible interfaces. This principle is useful for developing hydrogels that can reversibly stimulate cells mechanically or chemically in response to visible light. [ABSTRACT FROM AUTHOR]

Water-triggered shape memory polymers (SMPs) have been extensively studied for biomedical applications due to their advantages of non-thermal actuation capability. However, few studies have been carried out to explore the working principle of shape recovery onset, which is essentially determined by the complex reactions between polymer macromolecules and water molecules. In this study, we developed a phase separation model to describe the dynamic glass transition in water-triggered SMPs. Based on the phase transition theory, dense and dilute phase separations of polymer macromolecules can be achieved when the dynamic diffusions of water molecules in the SMPs undergo dehydration and absorption processes, respectively. Then, the dynamic glass transition is resulted from the dehydration and absorption of water molecules, leading to the dense and dilute phases in the SMPs. Therefore, a free-energy equation has been developed to characterize the recovery onset, in which the mixing free energy and elastic free energy are originated from the Flory–Huggins solution theory and phase separation model, respectively. Moreover, the glass transition and its connection to shape recovery behaviors, i.e. recovery ratio, relaxation time and dynamic mechanical modulus, have also been investigated, according to the Fick's diffusion law. Meanwhile, onset of programmable recovery has been explained by the dynamic phase separation, based on the transpiration theory and permeability model. Finally, the proposed model is verified using the experimental results reported in the literature. This study is expected to provide a fundamental approach to formulate the constitutive relationship between the dynamic phase separation and programmable recovery onset in the water-triggered SMPs. [ABSTRACT FROM AUTHOR]

The deposition of α-synuclein (α-Syn) in Lewy bodies serves as a prominent pathological hallmark of Parkinson's disease (PD). Recent research has revealed that α-Syn can undergo liquid–liquid phase separation (LLPS) during its fibrillization. Over time, the maturation of the resulting condensates leads to a liquid-to-solid phase transition (LSPT) ultimately resulting in the amyloid deposition in cells which is linked to the pathogenesis and development of PD. Herein, we summarize the understanding of α-Syn aggregation which can be described by nucleation and elongation steps to obtain insights into the correlation of protein aggregation, structural polymorphism, and PD progression. Additionally, we discuss the LLPS phenomena of α-Syn and heterotypic cross-amyloid interactions with a focus on aberrant LSPT in the aggregation process. Exploring the underlying mechanisms and interplay between α-Syn aberrant aggregation, pathological phase transitions, and PD pathogenesis will shed light on potential therapeutic interventions. [ABSTRACT FROM AUTHOR]

Protein self-assembly is a process that often occurs via liquid–liquid phase separation (LLPS), a sequence-specific and environmentally influenced phenomenon. Heuristic analysis of these self-assembling proteins has highlighted the conservation and importance of tyrosine residues and their ability to initiate LLPS and subsequent liquid–solid phase transitions. Generating tyrosine-templated constructs such as those found in nature serves as a promising method to generate responsive, self-assembling systems for a diverse range of applications. We discuss the importance of tyrosine in mediating the self-assembly of proteins, the interactions that enable this, and how it can be exploited for beneficial purposes. Protein self-assembly, guided by the interplay of sequence- and environment-dependent liquid–liquid phase separation (LLPS), constitutes a fundamental process in the assembly of numerous intrinsically disordered proteins. Heuristic examination of these proteins has underscored the role of tyrosine residues, evident in their conservation and pivotal involvement in initiating LLPS and subsequent liquid–solid phase transitions (LSPT). The development of tyrosine-templated constructs, designed to mimic their natural counterparts, emerges as a promising strategy for creating adaptive, self-assembling systems with diverse applications. This review explores the central role of tyrosine in orchestrating protein self-assembly, delving into key interactions and examining its potential in innovative applications, including responsive biomaterials and bioengineering. [ABSTRACT FROM AUTHOR]

The powerful adhesion systems of marine organisms have inspired the development of artificial protein-based bioadhesives. However, achieving robust wet adhesion using artificial bioadhesives remains technically challenging because the key element of liquid–liquid phase separation (LLPS)-driven complex coacervation in natural adhesion systems is often ignored. In this study, mimicking the complex coacervation phenomenon of marine organisms, an artificial protein-based adhesive hydrogel (SFG hydrogel) was developed by adopting the LLPS-mediated coacervation of the natural protein silk fibroin (SF) and the anionic surfactant sodium dodecylbenzene sulfonate (SDBS). The assembled SF/SDBS complex coacervate enabled precise spatial positioning and easy self-adjustable deposition on irregular substrate surfaces, allowing for tight contact. Spontaneous liquid-to-solid maturation promoted the phase transition of the SF/SDBS complex coacervate to form the SFG hydrogel in situ , enhancing its bulk cohesiveness and interfacial adhesion. The formed SFG hydrogel exhibited intrinsic advantages as a new type of artificial protein-based adhesive, including good biocompatibility, robust wet adhesion, rapid blood-clotting capacity, and easy operation. In vitro and in vivo experiments demonstrated that the SFG hydrogel not only achieved instant and effective hemostatic sealing of tissue injuries but also promoted wound healing and tissue regeneration, thus advancing its clinical applications. Marine mussels utilize the liquid–liquid phase separation (LLPS) strategy to induce the supramolecular assembly of mussel foot proteins, which plays a critical role in strong underwater adhesion of mussel foot proteins. Herein, an artificial protein-based adhesive hydrogel (named SFG hydrogel) was reported by adopting the LLPS-mediated coacervation of natural protein silk fibroin (SF) and anionic surfactant sodium dodecylbenzene sulfonate (SDBS). The assembled SFG hydrogel enabled the precise spatial positioning and easy self-adjustable deposition on substrate surfaces with irregularities, allowing tight interfacial adhesion and cohesiveness. The SFG hydrogel not only achieved instant and effective hemostatic sealing of tissue injuries but also promoted wound healing and tissue regeneration, exhibiting intrinsic advantages as a new type of artificial protein-based bioadhesives. [Display omitted] [ABSTRACT FROM AUTHOR]

The Allen-Cahn (AC) model is a mathematical equation that represents the phase separation process. The AC equation has numerous applications in various disciplines, such as image processing, physics, and biology. It models phase transitions, such as solidification and grain growth in materials, pattern formation in chemical reactions, and domain coarsening in biological systems like lipid membranes. Numerical methods are crucial for solving the AC equation due to its complexity and nonlinear nature. Analytical solutions are often extremely difficult to obtain. Therefore, the development of efficient numerical techniques is indispensable for approximating solutions and studying phase transitions, material behavior, and pattern formation accurately. We investigate the stability of an explicit finite difference method (FDM) used to numerically solve the two-dimensional (2D) AC model with a high-order polynomial potential, which was recently proposed to preserve a more intricate structure of interfaces. To demonstrate the precision and optimal estimate of our stability constraints, we conduct various computational tests using the derived time step formulas that ensure the maximum principle. [ABSTRACT FROM AUTHOR]

This paper focuses on phase and aggregation behavior for linear chains composed of blocks of hydrophilic and hydrophobic segments. Phase and conformational transitions of patterned chains are relevant for understanding liquid–liquid separation of biomolecular condensates, which play a prominent role in cellular biophysics and for surfactant and polymer applications. Previous studies of simple models for multiblock chains have shown that, depending on the sequence pattern and chain length, such systems can fall into one of two categories: displaying either phase separation or aggregation into finite-size clusters. The key new result of this paper is that both formation of finite-size aggregates and phase separation can be observed for certain chain architectures at appropriate conditions of temperature and concentration. For such systems, a bulk dense liquid condenses from a dilute phase that already contains multi-chain finite-size aggregates. The computational approach used in this study involves several distinct steps using histogram-reweighting grand canonical Monte Carlo simulations, which are described in some level of detail. [ABSTRACT FROM AUTHOR]

[Display omitted] Phase behavior of nanoconfined fluids adsorbed in metal–organic frameworks is of paramount importance for the design of advanced materials for energy and gas storage, separations, electrochemical devices, sensors, and drug delivery, as well as for the pore structure characterization. Phase transformations in adsorbed fluids often involve long-lasting metastable states and hysteresis that has been well-documented in gas adsorption–desorption and nonwetting fluid intrusion-extrusion experiments. However, theoretical prediction of the observed nanophase behavior remains a challenging problem. The mesoscopic canonical, or mesocanonical, ensemble (MCE) is devised to study the nanophase behavior under conditions of controlled fluctuations to stabilize metastable and labile states. Here, we implement and apply the MCE Monte Carlo (MCEMC) simulation scheme to predict the origins of reversible and hysteric adsorption phase transitions in a series of practical MOF materials, including IRMOF-1, ZIF-412, UiO-66, Cu-BTC, IRMOF-74-V, VII, and IX. The MCEMC method, called the gauge cell method, allows to produce Van der Waals type isotherms with distinctive swings around the phase transition regions. The constructed isotherms determine the positions of phase equilibrium and spinodals, as well as the nucleation barriers separating metastable states. We demonstrate the unique capabilities of the MCEMC method in quantitative predictions of experimental observations compared with the conventional grand canonical and canonical ensemble simulations. The MCEMC method is implemented in the open-source RASPA and LAMMPS software packages and recommended for studies of adsorption behavior and pore structure characterization of MOFs and other nanoporous materials. [ABSTRACT FROM AUTHOR]

Multiple power ultrasounds were employed to investigate the phase transition process of ternary Al81.5Cu14.7Bi3.8 immiscible alloy by various exerting modes. As the ultrasonic sources increased, the liquid phase separation pattern transformed from (Bi)-rich layered macrosegregation into the uniform distribution of secondary (Bi) droplets. Meanwhile, the primary (Al) phase evolved from coarse dendrites into plenty of small spherical grains and also tended to be uniformly dispersed. The subsequently formed ternary (Al) + (Al2Cu) + (Bi) monotectic structure, featured by the alternative (Al) and (Al2Cu) lamellar structure with fine (Bi) grains distributed, was coarsened first and then refined. Numerical simulations showed that the transient cavitation and the acoustic streaming strength were significantly enhanced by increasing ultrasonic beams, with the fourfold ultrasounds producing the most prominent effects on the phase separation process. The intensive and enlarged cavitation areas greatly accelerated the nucleation of both the secondary liquid phase and primary solid phase, which refined the growing (Bi) droplets and (Al) dendrites. The strength and morphology of acoustic streaming were the key factors in offsetting Stokes motion and carrying the growing grains to various regions, resulting in a uniform microstructure. Furthermore, increasing ultrasonic sources improved the friction and wear properties of the solidified alloy, which indicated that the Al81.5Cu14.7Bi3.8 immiscible alloy may become an excellent wear-resistant material owing to the uniform monotectic structure fabricated by the fourfold ultrasounds. [ABSTRACT FROM AUTHOR]

In striking contrast to equilibrium systems, inertia can profoundly alter the structure of active systems. Here, we demonstrate that driven systems can exhibit effective equilibrium-like states with increasing particle inertia, despite rigorously violating the fluctuation–dissipation theorem. Increasing inertia progressively eliminates motility-induced phase separation and restores equilibrium crystallization for active Brownian spheres. This effect appears to be general for a wide class of active systems, including those driven by deterministic time-dependent external fields, whose nonequilibrium patterns ultimately disappear with increasing inertia. The path to this effective equilibrium limit can be complex, with finite inertia sometimes acting to accentuate nonequilibrium transitions. The restoration of near equilibrium statistics can be understood through the conversion of active momentum sources to passive-like stresses. Unlike truly equilibrium systems, the effective temperature is now density dependent, the only remnant of the nonequilibrium dynamics. This density-dependent temperature can in principle introduce departures from equilibrium expectations, particularly in response to strong gradients. Our results provide additional insight into the effective temperature ansatz while revealing a mechanism to tune nonequilibrium phase transitions. [ABSTRACT FROM AUTHOR]

Phase transitions of proteins are strongly influenced by surface chemical modifications or mutations. Human γD-crystallin (HGD) single-mutants have been extensively studied because they are associated with the onset of juvenile cataract. However, they have also provided a rich library of molecules to examine how specific inter-protein interactions direct protein assembly, providing new insights and valuable experimental data for coarse-grained patchy-particle models. Here, we demonstrate that the addition of new inter-protein interactions by mutagenesis is additive and increases the number and variety of condensed phases formed by proteins. When double mutations incorporating two specific single point mutations are made, the properties of both single mutations are retained in addition to the formation of a new condensed phase. We find that the HGD double-mutant P23VC110M self-assembles into spherical particles with retrograde solubility, orthorhombic crystals, and needle/plate shape crystals, while retaining the ability to undergo liquid–liquid phase separation. This rich polymorphism is only partially predicted by the experimental data on the constituent single mutants. We also report a previously un-characterized amorphous protein particle, with unique properties that differ from those of protein spherulites, protein particulates previously described. The particles we observe are amorphous, reversible with temperature, tens of microns in size, and perfectly spherical. When they are grown on pristine surfaces, they appear to form by homogeneous nucleation, making them unique, and we believe a new form of protein condensate. This work highlights the challenges in predicting protein behavior, which has frustrated rational assembly and crystallization but also provides rich data to develop new coarse-grained models to explain the observed polymorphism. [ABSTRACT FROM AUTHOR]

In this research, by using different rheometric methods, the temperatures of phase transition for upper critical solution temperature phase diagram of polyethylene (PE) and poly(ethylene‐co‐vinyl acetate) (EVA) blends and filled systems with organically‐modified nanoclay (ONC) were measured. Since the PE/EVA‐based mixtures are widely applied in the film and foam industries, the evaluation of the phase behavior of these mixtures is of great importance. Microscopic observations show that ONC nanoparticles have a compatibilization role on the biphasic microstructure of PE/EVA. ONC nanoparticles have a remarkable impact on the viscoelastic properties of the EVA phase, leading to a reduction in the asymmetry of the viscoelastic properties of the two polymeric phases. The findings of this work focused on the isochronal dynamic temperature sweep tests on the well‐mixed and phase‐separated nanofiller‐filled systems with different cooling/heating rates indicated that these series of experiments did not have the necessary efficiency to determine the phase separation boundary and spinodal temperatures in thermodynamically equilibrium conditions. By using Han plot and dynamic temperature sweep tests at the minimum possible heating rate, 0.25 K/min, it was proved that by adding nanoparticles to PE/EVA blends, the area of well‐mixed region of the phase diagram did not show a significant increment. The pinning effects of nanoparticles on the polymeric chains and correspondingly, the reduction of molecular dynamics mainly affect the phase separation phenomenon. [ABSTRACT FROM AUTHOR]

Liquid-liquid phase separation (LLPS) of the mammalian prion protein is mainly driven by its intrinsically disordered N-terminal domain (N-PrP). However, the specific intermolecular interactions that promote LLPS remain largely unknown. Here, we used extensive mutagenesis and comparative analyses of evolutionarily distant PrP species to gain insight into the relationship between protein sequence and phase behavior. LLPS of mouse PrP is dependent on two polybasic motifs in N-PrP that are conserved in all tetrapods. A unique feature of mammalian N-PrP is the octarepeat domain with four histidines that mediate binding to copper ions. We now show that the octarepeat is critical for promoting LLPS and preventing the formation of PrP aggregates. Amphibian N-PrP, which contains the polybasic motifs but lacks a repeat domain and histidines, does not undergo LLPS and forms nondynamic protein assemblies indicative of aggregates. Insertion of the mouse octarepeat domain restored LLPS of amphibian N-PrP, supporting its essential role in regulating the phase transition of PrP. This activity of the octarepeat domain was neither dependent on the four highly conserved histidines nor on copper binding. Instead, the regularly spaced tryptophan residues were critical for regulating LLPS, presumably via cation–π interactions with the polybasic motifs. Our study reveals a novel role for the tryptophan residues in the octarepeat in controlling phase transition of PrP and indicates that the ability of mammalian PrP to undergo LLPS has evolved with the octarepeat in the intrinsically disordered domain but independently of the histidines. [ABSTRACT FROM AUTHOR]

The unique biophysical and biochemical properties of intrinsically disordered proteins (IDPs) and their recombinant derivatives, intrinsically disordered protein polymers (IDPPs) offer opportunities for producing multistimuli‐responsive materials; their sequence‐encoded disorder and tendency for phase separation facilitate the development of multifunctional materials. This review highlights the strategies for enhancing the structural diversity of elastin‐like polypeptides (ELPs) and resilin‐like polypeptides (RLPs), and their self‐assembled structures via genetic fusion to ordered motifs such as helical or beta sheet domains. In particular, this review describes approaches that harness the synergistic interplay between order‐promoting and thermoresponsive building blocks to design hybrid biomaterials, resulting in well‐structured, stimuli‐responsive supramolecular materials ordered on the nanoscale. [ABSTRACT FROM AUTHOR]

Phase separation and percolation contribute to phase transitions of multivalent macromolecules. Contributions of percolation are evident through the viscoelasticity of condensates and through the formation of heterogeneous distributions of nano- and mesoscale pre-percolation clusters in sub-saturated solutions. Here, we show that clusters formed in sub-saturated solutions of FET (FUS-EWSR1-TAF15) proteins are affected differently by glutamate versus chloride. These differences on the nanoscale, gleaned using a suite of methods deployed across a wide range of protein concentrations, are prevalent and can be unmasked even though the driving forces for phase separation remain unchanged in glutamate versus chloride. Strikingly, differences in anion-mediated interactions that drive clustering saturate on the micron-scale. Beyond this length scale the system separates into coexisting phases. Overall, we find that sequence-encoded interactions, mediated by solution components, make synergistic and distinct contributions to the formation of pre-percolation clusters in sub-saturated solutions, and to the driving forces for phase separation. Biomolecular condensates form via phase separation of multivalent macromolecules. Phase separation is governed by solubility whereas multivalence drives percolation, also known as gelation. The authors in this work identify the distinct energy and length scales that influence phase separation versus percolation. [ABSTRACT FROM AUTHOR]

Liquid–liquid phase separation (LLPS) is an emerging phenomenon in cell physiology and diseases. The weak multivalent interaction prerequisite for LLPS is believed to be facilitated through intrinsically disordered regions, which are prevalent in neurodegenerative disease-associated proteins. These aggregation-prone proteins also exhibit an inherent property for phase separation, resulting in protein-rich liquid-like droplets. The very high local protein concentration in the water-deficient confined microenvironment not only drives the viscoelastic transition from the liquid to solid-like state but also most often nucleate amyloid fibril formation. Indeed, protein misfolding, oligomerization, and amyloid aggregation are observed to be initiated from the LLPS of various neurodegeneration-related proteins. Moreover, in these cases, neurodegeneration-promoting genetic and environmental factors play a direct role in amyloid aggregation preceded by the phase separation. These cumulative recent observations ignite the possibility of LLPS being a prominent nucleation mechanism associated with aberrant protein aggregation. The present review elaborates on the nucleation mechanism of the amyloid aggregation pathway and the possible early molecular events associated with amyloid-related protein phase separation. It also summarizes the recent advancement in understanding the aberrant phase transition of major proteins contributing to neurodegeneration focusing on the common disease-associated factors. Overall, this review proposes a generic LLPS-mediated multistep nucleation mechanism for amyloid aggregation and its implication in neurodegeneration. [ABSTRACT FROM AUTHOR]

This document provides a list of references for scientific articles related to stress memory and phase separation in plants. The articles cover various topics, including the molecular mechanisms of stress memory, the formation of liquid-liquid phase separation in cells, and the role of specific proteins in stress adaptation. These references serve as a valuable resource for further research on the subject. [Extracted from the article]

Powder bed fusion (PBF) is an attractive additive manufacturing option for fabrication of SiC object with complex geometries. However, the density and microstructure controls remain a challenge. This study is aimed at understanding laser–SiC interactions, with emphasis on microstructure‐processing relationships, to identify potential solutions for the process improvement. SiC tubes were fabricated by PBF of pure SiC powders without sintering additives. Comprehensive analysis by X‐ray diffraction, Raman spectroscopy, and electron microscopy indicated that binding of SiC particles was achieved by incongruent melting of SiC to a Si/C mixture containing SiC micro‐ and nanocrystallites. The phase evolution under laser irradiation of SiC was explained by phase diagrams. This study uncovered the PBF SiC microstructure at different length scales and the relationship between the microstructure and the processing parameters. [ABSTRACT FROM AUTHOR]

Parkinson's disease (PD), the second most common neurodegenerative disorder, is linked to α-synuclein (α-Syn) aggregation. Despite no specific drug being available for its treatment, curcumin, from the spice turmeric, shows promise. However, its application in PD is limited by a lack of understanding of its anti-amyloidogenic mechanisms. In this study, we first reconstructed the liquid–liquid phase separation (LLPS) of α-Syn in vitro under different conditions, which may be an initial step in entraining the pathogenic aggregation. Subsequently, we evaluated the effects of curcumin on the formation of droplets, oligomers, and aggregated fibers during the LLPS of α-synuclein, as well as its impact on the toxicity of aggregated α-synuclein to cultured cells. Importantly, we found that curcumin can inhibit amyloid formation by inhibiting the occurrence of LLPS and the subsequent formation of oligomers of α-Syn in the early stages of aggregation. Finally, the molecular dynamic simulations of interactions between α-Syn decamer fibrils and curcumin showed that van der Waal's interactions make the largest contribution to the anti-aggregation effect of curcumin. These results may help to clarify the mechanism by which curcumin inhibits the formation of α-Syn aggregates during the development of PD. [ABSTRACT FROM AUTHOR]

Intracellular aggregation of fused in sarcoma (FUS) is associated with the pathogenesis of familial amyotrophic lateral sclerosis (ALS). Under stress, FUS forms liquid droplets via liquid–liquid phase separation (LLPS). Two types of wild-type FUS LLPS exist in equilibrium: low-pressure LLPS (LP-LLPS) and high-pressure LLPS (HP-LLPS); the former dominates below 2 kbar and the latter over 2 kbar. Although several disease-type FUS variants have been identified, the molecular mechanism underlying accelerated cytoplasmic granule formation in ALS patients remains poorly understood. Herein, we report the reversible formation of the two LLPS states and the irreversible liquid–solid transition, namely droplet aging, of the ALS patient-type FUS variant R495X using fluorescence microscopy and ultraviolet–visible absorption spectroscopy combined with perturbations in pressure and temperature. Liquid-to-solid phase transition was accelerated in the HP-LLPS of R495X than in the wild-type variant; arginine slowed the aging of droplets at atmospheric conditions by inhibiting the formation of HP-LLPS more selectively compared to that of LP-LLPS. Our findings provide new insight into the mechanism by which R495X readily forms cytoplasmic aggregates. Targeting the aberrantly formed liquid droplets (the HP-LLPS state) of proteins with minimal impact on physiological functions could be a novel therapeutic strategy for LLPS-mediated protein diseases. [ABSTRACT FROM AUTHOR]

In practical applications, LiCoO2 (LCO) cathode is usually charged with a constant current plus constant voltage (CC+CV) procedure to obtain higher capacity delivery. However, the harsh condition upon CC+CV procedure causes the accelerated capacity decay of LCO. Herein, the fading mechanism of LCO cycling upon CC+CV procedure at 4.6 V versus Li/Li+ is first revealed. Comparing with a pure CC charging, the accelerated capacity decay of LCO upon CC+CV procedure is attributed to both the bulk and surface structure damages: i) the CV charging triggers more H1‐3 phase separation, leading to the generation of lattice dislocations, curved Co‐O layers, and ultimately the bulk microcracks inside the LCO particles; ii) upon cycle, the CV charging causes more side reactions and more surface structure collapse issues, including forming thick surface phase transition layer (PTL), causing more Co dissolution, forming thick and loose CEI layer, etc., which seriously increases the charge transfer resistance and reduces the interface Li+ transport kinetics. This work provides a new insight into the fading mechanism, and shows a new pathway for designing more advanced LCO cathodes. [ABSTRACT FROM AUTHOR]

Focal adhesions (FAs) are transmembrane protein assemblies mediating cell-matrix connection. Although protein liquid-liquid phase separation (LLPS) has been tied to the organization and dynamics of FAs, the underlying mechanisms remain unclear. Here, we experimentally tune the LLPS of PXN/Paxillin, an essential scaffold protein of FAs, by utilizing a light-inducible Cry2 system in different cell types. In addition to nucleating FA components, light-triggered PXN LLPS potently activates integrin signaling and subsequently accelerates cell spreading. In contrast to the homotypic interaction-driven LLPS of PXN in vitro, PXN condensates in cells are associated with the plasma membrane and modulated by actomyosin contraction and client proteins of FAs. Interestingly, non-specific weak intermolecular interactions synergize with specific molecular interactions to mediate the multicomponent condensation of PXN and are efficient in promoting FA assembly and integrin signaling. Thus, our data establish an active role of the PXN phase transition into a condensed membrane-associated compartment in promoting the assembly/maturation of FAs. [ABSTRACT FROM AUTHOR]

Membraneless organelles (MLOs) are likely assembled via liquid–liquid phase separation (LLPS). The liquid‐like MLOs afford multifold peculiarities including high dynamics, reversibility and responsiveness. It is common to see fast, drastic, and reversible formation and dissolution events of MLOs, as well as transition into more stable glassy or gel‐like states, which suggests a metastable assembly state. Moreover, the alteration of metastability of LLPS is linked with cellular pathology. Here, we review the "metastability" related to MLOs driven by liquid phase separation, from multifaceted regards including energy state, molecular interactions, molecular structure, phase transition, as well as the associations with diseases. This review can help to advance the insight into properties and pathogenesis associated with LLPS of biological matter. Key points: Liquid–liquid phase separation emerges as a universal tool for the intracellular biomolecule organization, particularly via the formation of membraneless organelles.The liquid‐like membraneless organelles afford unique properties and have aroused wide interests among cell biologists.Metastability is a general feature of liquid‐like membraneless organelles, which has manifested in multiple aspects including energy state, molecular interactions, molecular structures, biological assemblages and its association with diseases.Understanding of metastability of biological liquid phase separation can not only help to elucidate the formation and properties of membraneless organelles, but also pave the way to the insight into pathogenesis. [ABSTRACT FROM AUTHOR]

In this work, a novel series of oxyfluoride glasses‐ceramics (GCs) is developed by enhancing the phase separation through the substitution of LaF3 for La2O3. The thus‐derived GCs exhibit a remarkable 2700‐fold increase in up‐conversion (UC) luminescence of Er3+ ions compared to the precursor glass. From the 19F Nuclear Magnetic Resonance analysis, this enhancement is attributed to the structural disorder‐to‐order transition in the fluoride‐rich phase. Upon isothermal heat treatment, the translucent GCs transform into transparent ones, making UC luminescence even stronger. The enhanced UC luminescence leads to strong temperature‐sensing ability of the studied glasses. The nano‐micro phase separation is clarified by atomistic simulations and scanning electron microscopy. This study implies that phase separation engineering is a powerful way to achieve superior photonic performances. [ABSTRACT FROM AUTHOR]

Cells contain a myriad of membraneless ribonucleoprotein (RNP) condensates with distinct compositions of proteins and RNAs. RNP condensates participate in different cellular activities, including RNA storage, mRNA translation or decay, stress response, etc. RNP condensates are assembled via liquid‐liquid phase separation (LLPS) driven by multivalent interactions. Transition of RNP condensates into bodies with abnormal material properties, such as solid‐like amyloid structures, is associated with the pathogenesis of various diseases. In this review, we focus on how RNAs regulate multiple aspects of RNP condensates, such as dynamic assembly and/or disassembly and biophysical properties. RNA properties – including concentration, sequence, length and structure – also determine the phase behaviors of RNP condensates. RNA is also involved in specifying autophagic degradation of RNP condensates. Unraveling the role of RNA in RNPs provides novel insights into pathological accumulation of RNPs in various diseases. This new understanding can potentially be harnessed to develop therapeutic strategies. [ABSTRACT FROM AUTHOR]

(Zr 0.196 Hf 0.02 V 0.196 Nb 0.196 Mo 0.196 W 0.196)C x complex concentrated ceramics (CCC) with variable carbon non-stoichiometry are fabricated by hot-pressing sintering at 2100 °C for 1 h. The influence of carbon content on phase decomposition behavior and microstructural evolution is investigated. With the decreasing carbon content, the phase transformation of single-phase solid solution → discontinuous precipitation → spinodal decomposition → single-phase occurs, consistent to the binary phase diagram with miscibility gap. The single-phase solid solution decomposes into (ZrHfNb)C-rich and (VMoW)C-rich phases during the phase separation. For spinodal decomposition, the nodular microstructure is formed with coherent crystal orientation relationship of (ZrHfNb)C-rich phase {011} // (VMoW)C-rich phase {011}. The spinodal decomposition leads to in-situ hardening and toughening effects due to the interface hardening and fine microstructure. The spinodal decomposition into two high entropy phases could potentially be beneficial to tailor properties and demonstrated in a future work. [ABSTRACT FROM AUTHOR]

Numerous biological systems contain vesicle‐like biomolecular compartments without membranes, which contribute to diverse functions including gene regulation, stress response, signaling, and skin barrier formation. Coacervation, as a form of liquid–liquid phase separation (LLPS), is recognized as a representative precursor to the formation and assembly of membrane‐less vesicle‐like structures, although their formation mechanism remains unclear. In this study, a coacervation‐driven membrane‐less vesicle‐like structure is constructed using two proteins, GG1234 (an anionic intrinsically disordered protein) and bhBMP‐2 (a bioengineered human bone morphogenetic protein 2). GG1234 formed both simple coacervates by itself and complex coacervates with the relatively cationic bhBMP‐2 under acidic conditions. Upon addition of dissolved bhBMP‐2 to the simple coacervates of GG1234, a phase transition from spherical simple coacervates to vesicular condensates occurred via the interactions between GG1234 and bhBMP‐2 on the surface of the highly viscoelastic GG1234 simple coacervates. Furthermore, the shell structure in the outer region of the GG1234/bhBMP‐2 vesicular condensates exhibited gel‐like properties, leading to the formation of multiphasic vesicle‐like compartments. A potential mechanism is proposed for the formation of the membrane‐less GG1234/bhBMP‐2 vesicle‐like compartments. This study provides a dynamic process underlying the formation of biomolecular multiphasic condensates, thereby enhancing the understanding of these biomolecular structures. [ABSTRACT FROM AUTHOR]

Motility-induced phase separation (MIPS) is the hallmark of non-equilibrium phase transition in active matter. Here, by means of Brownian dynamics simulations, we determine the phase behavior and the critical point for phase separation induced by motility of a two-dimensional system of soft active Brownian particles, whose interaction is modeled by the generalized purely repulsive Weeks–Chandler–Andersen potential. We refer to this model as soft active Brownian particles. We determine and analyze the influence of particle softness on the MIPS and show that the liquid–gas coexistence region is wider, the softer the interparticle interactions becomes. Moreover, the critical value of the self-propulsion velocity at which diluted and dense phases start to coexist also increases; as a consequence, the softer the particle interaction is, the bigger self-propulsion velocities are needed in order to observe a MIPS. [ABSTRACT FROM AUTHOR]

A deep understanding for collective behavior in an active matter system with complex interactions has far-reaching impact in biology. In the present work, we adopt Langevin dynamics simulations to investigate diffusion dynamics and phase separation in an anisotropic active particle system with a tunable biased angle α defined as the deviation between the active force direction and anisotropic orientation. Our results demonstrate that the biased angle can induce super-rotational diffusion dynamics characterized by a power-law relationship between the mean square angle displacement (MSAD) and the time interval Δt in the form of MSAD ∼ Δtβ with β > 1 and also result in non-trivial phase separation kinetics. As activity is dominant, nucleation time shows a non-monotonic dependence on the biased angle. Moreover, there arises a distinct transition of phase separation, from spinodal decomposition without apparent nucleation time to binodal decomposition with prominent nucleation delay. A significant inhibition effect occurs at right and obtuse angles, where the remarkable super-rotational diffusion prevents particle aggregation, leading to a slow nucleation process. As active force is competitive to anisotropic interactions, the system is almost homogeneous, while, intriguingly, we observe a re-entrant phase separation as a small acute angle is introduced. The prominent super-rotational diffusion under small angles provides an optimum condition for particle adsorption and cluster growth and, thus, accounts for the re-entrance of phase separation. A consistent scenario for the physical mechanism of our observations is achieved by properly considering the modulation of the biased angle on the interplay between activity and anisotropic interactions. [ABSTRACT FROM AUTHOR]

If a binary liquid mixture, composed of two alternative species with equal amounts, is quenched from a high temperature to a low temperature, below the critical point of demixing, then the mixture will phase separate through a process known as spinodal decomposition. However, if the two alternative species are allowed to interconvert, either naturally (e.g., the equilibrium interconversion of enantiomers) or forcefully (e.g., via an external source of energy or matter), then the process of phase separation may drastically change. In this case, depending on the nature of interconversion, two phenomena could be observed: either phase amplification, the growth of one phase at the expense of another stable phase, or microphase separation, the formation of nongrowing (steady-state) microphase domains. In this work, we phenomenologically generalize the Cahn–Hilliard theory of spinodal decomposition to include the molecular interconversion of species and describe the physical properties of systems undergoing either phase amplification or microphase separation. We apply the developed phenomenology to accurately describe the simulation results of three atomistic models that demonstrate phase amplification and/or microphase separation. We also discuss the application of our approach to phase transitions in polyamorphic liquids. Finally, we describe the effects of fluctuations of the order parameter in the critical region on phase amplification and microphase separation. [ABSTRACT FROM AUTHOR]

Liquid–liquid phase separation of fluids exhibiting interconversion between alternative states has been proposed as an underlying mechanism for fluid polyamorphism and may be of relevance to the protein function and intracellular organization. However, molecular-level insight into the interplay between competing forces that can drive or restrict phase separation in interconverting fluids remains elusive. Here, we utilize an off-lattice model of enantiomers with tunable chiral interconversion and interaction properties to elucidate the physics underlying the stabilization and tunability of phase separation in fluids with interconverting states. We show that introducing an imbalance in the intermolecular forces between two enantiomers results in nonequilibrium, arrested phase separation into microdomains. We also find that in the equilibrium case, when all interaction forces are conservative, the growth of the phase domain is restricted only by the system size. In this case, we observe phase amplification, in which one of the two alternative phases grows at the expense of the other. These findings provide novel insights on how the interplay between dynamics and thermodynamics defines the equilibrium and steady-state morphologies of phase transitions in fluids with interconverting molecular or supramolecular states. [ABSTRACT FROM AUTHOR]

The formed morphology during phase separation is crucial for determining the properties of the resulting product, e.g., a functional membrane. However, an accurate morphology prediction is challenging due to the inherent complexity of molecular interactions. In this study, the phase separation of a two-dimensional model polymer solution is investigated. The spinodal decomposition during the formation of polymer-rich domains is described by the Cahn–Hilliard equation incorporating the Flory–Huggins free energy description between the polymer and solvent. We circumvent the heavy burden of precise morphology prediction through two aspects. First, we systematically analyze the degree of impact of the parameters (initial polymer volume fraction, polymer mobility, degree of polymerization, surface tension parameter, and Flory–Huggins interaction parameter) in a phase-separating system on morphological evolution characterized by geometrical fingerprints to determine the most influential factor. The sensitivity analysis provides an estimate for the error tolerance of each parameter in determining the transition time, the spinodal decomposition length, and the domain growth rate. Secondly, we devise a set of physics-informed neural networks (PINN) comprising two coupled feedforward neural networks to represent the phase-field equations and inversely discover the value of the embedded parameter for a given morphological evolution. Among the five parameters considered, the polymer–solvent affinity is key in determining the phase transition time and the growth law of the polymer-rich domains. We demonstrate that the unknown parameter can be accurately determined by renormalizing the PINN-predicted parameter by the change of characteristic domain size in time. Our results suggest that certain degrees of error are tolerable and do not significantly affect the morphology properties during the domain growth. Moreover, reliable inverse prediction of the unknown parameter can be pursued by merely two separate snapshots during morphological evolution. The latter largely reduces the computational load in the standard data-driven predictive methods, and the approach may prove beneficial to the inverse design for specific needs. [ABSTRACT FROM AUTHOR]

A simple model is introduced to describe phase behaviours of binary mixtures of a thermoreversible gel and a low-molecular-weight liquid crystal (LC). We predict novel phase diagrams on the temperature–concentration plane, including sol–gel transition, nematic–isotropic phase transition, and phase separation. At high temperatures, the phase separation between the isotropic sol and gel phases appears. As the temperature decreases, we have the phase separation between nematic sol and isotropic gel phases, in which the nematic domains are dispersed in the isotropic gel phase. We suggest that thermoreversible gelation of reactive molecules mixed with LCs will become one of the new classes of polymer-dispersed liquid crystals. [ABSTRACT FROM AUTHOR]

The impact of the interaction strength between polymer and nanoparticles (NPs), εNP, on the glass transition temperature, Tg, and the phase separation in polymer nanocomposites (PNCs) is explored by employing molecular dynamics simulations. The variation of the Tg with respect to εNP shows interesting behaviors at low and high-volume fractions of nanoparticles (fNP). For εNP < 2, the Tg curves seem to diverge, whereas for εNP > 2, they almost coincide. Interestingly, no sign of any phase separation is witnessed in the investigated PNCs at low fNP. However, at high fNP, obvious phase separation is noticed for low εNP. For both cases, there is no phase separation for εNP > 2. The measurement of the diffusion constants also reveals that the polymer dynamics become independent of the volume fraction of NPs for εNP > 2. We strongly recommend considering this critical value of εNP to avoid phase separation and Tg instability in the case of a high-volume fraction of NPs incorporated into PNCs. Briefly, different behaviors of Tg as the interaction strength between nanoparticles and polymer is increased in relevance to different inserted volume fractions of NPs are observed. Thus, the findings of this work could yield a high impact on the experimental techniques implemented in the fabrication and characterization of NPs–Polymers nanocomposites. [ABSTRACT FROM AUTHOR]

Antimicrobial peptides (AMPs), which combat bacterial infections by disrupting the bacterial cell membrane or interacting with intracellular targets, are naturally produced by a number of different organisms, and are increasingly also explored as therapeutics. However, the mechanisms by which AMPs act on intracellular targets are not well understood. Using machine learning-based sequence analysis, we identified a significant number of AMPs that have a strong tendency to form liquid-like condensates in the presence of nucleic acids through phase separation. We demonstrate that this phase separation propensity is linked to the effectiveness of the AMPs in inhibiting transcription and translation in vitro, as well as their ability to compact nucleic acids and form clusters with bacterial nucleic acids in bacterial cells. These results suggest that the AMP-driven compaction of nucleic acids and modulation of their phase transitions constitute a previously unrecognised mechanism by which AMPs exert their antibacterial effects. The development of antimicrobials that target nucleic acid phase transitions may become an attractive route to finding effective and long-lasting antibiotics. In this work the authors describe antimicrobial peptides (AMPs)-driven phase transitions of intracellular nucleic acids, whereby AMPs induce compaction and phase separation of nucleic acids, resulting in their sequestration and eventual cell death. [ABSTRACT FROM AUTHOR]

Some debatable aspects of interpretation of binary phase diagrams playing a key role in the science of alloys are considered. It is shown that the ordering – separation phase transition in binary alloys changes the sign of the chemical interatomic interaction at some temperatures. The mismatch between the mechanism of this process and its representation in the phase diagram is discussed. It is suggested that some concepts on the ranges of the diagram, where the structural changes occur by diffusion, should be revised. [ABSTRACT FROM AUTHOR]

All‐polymer solar cells (All‐PSCs) are considered to be the most promising candidates for realizing efficient and stable organic solar cells (OSCs). However, the challenge of controlling morphology has hindered the performance of All‐PSCs. Compared to small molecule acceptors, polymer acceptors play a more crucial role in obtaining an ideal morphology for All‐PSCs. The molecular weight of polymer acceptors is one of the key factors determining the morphological and mechanical properties as well as the interactions with donors. Herein, by using a monomer of PYIT (PYIT1) and PYITs with low (PYIT2) and high (PYIT3) molecular weights, the impact of molecular weight of the polymer acceptor is systematically investigated on the phase transition process, morphological, and photovoltaic properties. It is found that tuning the molecular weight effectively regulates the phase transition process of the polymer acceptor and its interaction with the polymer donor. This induces significant effects on the aggregation behaviors of the polymers. Appropriate molecular weight polymer acceptors can facilitate favorable phase separation morphology. With PBQx‐Cl as the donor and PYIT2 as acceptor, a high‐performance binary All‐PSC is achieved with an efficiency of 18.39%. This study provides deep insights into the performance enhancement of All‐PSCs through rational polymer acceptor design. [ABSTRACT FROM AUTHOR]

Exploring the role of phase separation in intracellular compartment formation is an active area of research. However, the associations of phase separation with intestinal stem cell (ISC)-dependent regeneration and aging remain unclear. Here, we demonstrate that BuGZ, a coacervating mitotic effector, shows age- and injury-associated condensation in Drosophila ISC nuclei during interphase. BuGZ condensation promotes ISC proliferation, affecting Drosophila gut repair and longevity. Moreover, m6A reader YT521-B acts as the transcriptional and functional downstream of BuGZ. The binding of YT521-B promotor or m6A writer Ime4/ Mettl14 to BuGZ controls its coacervation, indicating that the promotor may accelerate the phase transition of its binding transcription factor. Hence, we propose that phase separation and m6A regulators may be critical for ameliorating ISC-dependent gut regeneration and aging and requires further study. Phase separation serves to compartmentalize and concentrate cellular components to facilitate essential physiological processes. Here, the authors elucidate the role and mechanism of BuGZ-mediated phase separation in the context of gut regeneration and aging. [ABSTRACT FROM AUTHOR]

We determined the phase boundaries of aqueous mixtures containing colloidal rod-like fd-viruses and polystyrene spheres using diffusing-wave spectroscopy and compared the results with free volume theory predictions. Excluded volume interactions in mixtures of colloidal rods and spheres lead to mediated depletion interactions. The strength and range of this attractive interaction depend on the concentrations of the particles, the length L and diameter D of the rods, and the radius R of the spheres. At strong enough attraction, this depletion interaction leads to phase separation. We experimentally determined the rod and sphere concentrations where these phase transitions occur by systematically varying the size ratios L/R and D/R and the aspect ratio L/D. This was done by using spheres with different radii and modifying the effective diameter of the rods through either the ionic strength of the buffer or anchoring a polymeric brush to the surface of the rods. The observed phase transitions were from a binary fluid to a colloidal gas/liquid phase coexistence that occurred already at very low concentrations due to the depletion efficiency of highly anisotropic rods. The experimentally measured phase transitions were compared to phase boundaries obtained using free volume theory (FVT), a well established theory for calculating the phase behavior of colloidal particles mixed with depletants. We find good correspondence between the experimental phase transitions and the theoretical FVT model where the excluded volume of the rod-like depletants was explicitly accounted for in both the reservoir and the system. [ABSTRACT FROM AUTHOR]

The shapes of bacteria can vary widely; they may, for instance, be spherical, rod-like, string-like, or curved. In general, bacilli are highly anisotropic. For research and (bio)technological purposes, it can be useful to concentrate bacteria, which is possible by adding nonadsorbing polymers. The induced phase separation originates from a polymer-mediated depletion interaction, first understood by Asakura and Oosawa. Here, it is shown that free volume theory (FVT) can semi-quantitatively describe the phase transitions observed when adding sodium polystyrene sulfonate polymers to E. coli bacteria [Schwarz-Linek et al., Soft Matter 6, 4540 (2010)] at high ionic strength. The E. coli bacteria are described as short, hard spherocylinders. FVT predicts that the phase transitions of the mixtures result from a fluid–ABC crystal solid phase coexistence of a hard spherocylinder–polymer mixture. [ABSTRACT FROM AUTHOR]

Protein function can be modulated by phase transitions in their material properties, which can range from liquid- to solid-like; yet, the mechanisms that drive these transitions and whether they are important for physiology are still unknown. In the model plant Arabidopsis, we show that developmental robustness is reinforced by phase transitions of the plasma membrane-bound lipid-binding protein SEC14-like. Using imaging, genetics, and in vitro reconstitution experiments, we show that SEC14-like undergoes liquid-like phase separation in the root stem cells. Outside the stem cell niche, SEC14-like associates with the caspase-like protease separase and conserved microtubule motors at unique polar plasma membrane interfaces. In these interfaces, SEC14-like undergoes processing by separase, which promotes its liquid-to-solid transition. This transition is important for root development, as lines expressing an uncleavable SEC14-like variant or mutants of separase and associated microtubule motors show similar developmental phenotypes. Furthermore, the processed and solidified but not the liquid form of SEC14-like interacts with and regulates the polarity of the auxin efflux carrier PINFORMED2. This work demonstrates that robust development can involve liquid-to-solid transitions mediated by proteolysis at unique plasma membrane interfaces. The mechanisms that drive protein phase transitions are unclear. This study in plants shows that an intracellular liquid condensate formed by the lipid transferase SFH8 associates with membranes; when a short fragment of SFH8 is removed by the caspase-like protease ESP, it transforms into a solid filament that can modulate root development. [ABSTRACT FROM AUTHOR]

Thermoresponsive polysaccharide-based materials with tunable transition temperatures regulating phase-separated microdomains offer substantial opportunities in tissue engineering and biomedical applications. To develop novel synthetic thermoresponsive polysaccharides, we employed versatile chemical routes to attach hydrophobic adducts to the backbone of hydrophilic dextran and gradually increased the hydrophobicity of the dextran chains to engineer phase separation. Conjugating methacrylate moieties to the dextran backbone yielded a continuous increase in macromolecular hydrophobicity that induced a reversible phase transition whose lower critical solution temperature can be modulated via variations in polysaccharide concentration, molecular weight, degree of methacrylation, ionic strength, surfactant, urea and Hofmeister salts. The phase separation is driven by increased hydrophobic interactions of methacrylate residues, where the addition of surfactant and urea disassociates hydrophobic interactions and eliminates phase transition. Morphological characterization of phase-separated dextran solutions via scanning electron and flow imaging microscopy revealed the formation of microdomains upon phase transition. These novel thermoresponsive dextrans exhibited promising cytocompatibility in cell culture where the phase transition exerted negligible effects on the attachment, spreading and proliferation of human dermal fibroblasts. Leveraging the conjugated methacrylate groups, we employed photo-initiated radical polymerization to generate phase-separated hydrogels with distinct microdomains. Our bottom-up approach to engineering macromolecular hydrophobicity of conventional hydrophilic, non-phase separating dextrans to induce robust phase transition and generate thermoresponsive phase-separated biomaterials will find applications in mechanobiology, tissue repair and regenerative medicine. [ABSTRACT FROM AUTHOR]

Chemicals or drugs can accumulate within biomolecular condensates formed through phase separation in cells. Here, we use super-resolution imaging to search for chemicals that induce phase transition within chromatin at the microscale. This microscopic screening approach reveals that adriamycin (doxorubicin) — a widely used anticancer drug that is known to interact with chromatin — specifically induces visible local condensation and global conformational change of chromatin in cancer and primary cells. Hi-C and ATAC-seq experiments systematically and quantitatively demonstrate that adriamycin-induced chromatin condensation is accompanied by weakened chromatin interaction within topologically associated domains, compartment A/B switching, lower chromatin accessibility, and corresponding transcriptomic changes. Mechanistically, adriamycin complexes with histone H1 and induces phase transition of H1, forming fibrous aggregates in vitro. These results reveal a phase separation-driven mechanism for a chemotherapeutic drug. The authors show that adriamycin induces global changes on chromatin conformation associated with phase transitions mediated through Histone H1. [ABSTRACT FROM AUTHOR]

Biochemical reactions occurring in highly crowded cellular environments require different means of control to ensure productivity and specificity. Compartmentalization of reagents by liquid‐liquid phase separation is one of these means. However, extremely high local protein concentrations of up to 400 mg/ml can result in pathological aggregation into fibrillar amyloid structures, a phenomenon that has been linked to various neurodegenerative diseases. Despite its relevance, the process of liquid‐to‐solid transition inside condensates is still not well understood at the molecular level. We thus herein use small peptide derivatives that can undergo both liquid‐liquid and subsequent liquid‐to‐solid phase transition as model systems to study both processes. Using solid‐state nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM), we compare the structure of condensed states of leucine, tryptophan and phenylalanine containing derivatives, distinguishing between liquid‐like condensates, amorphous aggregates and fibrils, respectively. A structural model for the fibrils formed by the phenylalanine derivative was obtained by an NMR‐based structure calculation. The fibrils are stabilised by hydrogen bonds and side‐chain π‐π interactions, which are likely much less pronounced or absent in the liquid and amorphous state. Such noncovalent interactions are equally important for the liquid‐to‐solid transition of proteins, particularly those related to neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Liquid-liquid phase separation (LLPS, also known as biomolecular condensation) and the related biogenesis of various membraneless organelles (MLOs) and biomolecular condensates (BMCs) are now considered fundamental molecular mechanisms governing the spatiotemporal organization of the intracellular space [[1], [3], [5]]. Biological Liquid-Liquid Phase Separation, Biomolecular Condensates, and Membraneless Organelles: Now You See Me, Now You Don't Droplets of Life: Membrane-Less Organelles, Biomolecular Condensates, and Biological Liquid-Liquid Phase Separation1st ed.Uversky V.N.; Elsevier: Amsterdam, The Netherlands. For example, deletion of the aggregation-prone domain (APD) significantly inhibited self-condensation, whereas the Nst1 mutant with the deleted multivalent polyampholyte domain (PD) within the intrinsically disordered region (Nst1 SB PD sb ) was able to form self-condensates but failed to interact and condensate Dcp2, a decapping protein and PB component. [Extracted from the article]