Dilute Phase Research Articles

Exogenous Pregnane X Receptor Does Not Undergo Liquid-Liquid Phase Separation in Nucleus under Cell-Based In Vitro Conditions.

Pregnane X receptor (PXR) belongs to the nuclear receptor superfamily that plays a crucial role in hepatic physiologic and pathologic conditions. Phase separation is a process in which biomacromolecules aggregate and condense into a dense phase as liquid condensates and coexist with a dilute phase, contributing to various cellular and biologic functions. Until now, whether PXR could undergo phase separation remains unclear. This study aimed to investigate whether PXR undergoes phase separation. Analysis of the intrinsically disordered regions (IDRs) using algorithm tools indicated a low propensity of PXR to undergo phase separation. Experimental assays such as hyperosmotic stress, agonist treatment, and optoDroplets assay demonstrated the absence of phase separation for PXR. OptoDroplets assay revealed the inability of the fusion protein of Cry2 with PXR to form condensates upon blue light stimulation. Moreover, phase separation of PXR did not occur even though the mRNA and protein expression levels of PXR target, cytochrome P450 3A4, changed after sorbitol treatment. In conclusion, for the first time, these findings suggested that exogenous PXR does not undergo phase separation following activation or under hyperosmotic stress in nucleus of cells. SIGNIFICANCE STATEMENT: PXR plays a critical role in hepatic physiological and pathological processes. The present study clearly demonstrated that exogenous PXR does not undergo phase separation after activation by agonist or under hyperosmotic stress in nucleus. These findings may help understand PXR biology.

A complex network of interdomain interactions underlies the conformational ensemble of monomeric TDP-43 and modulates its phase behavior.

TAR DNA-binding protein 43 (TDP-43) is a multidomain protein involved in the regulation of RNA metabolism, and its aggregates have been observed in neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Numerous studies indicate TDP-43 can undergo liquid-liquid phase separation (LLPS) in vitro and is a component of biological condensates. Homo-oligomerization via the folded N-terminal domain (aa:1-77) and the conserved helical region (aa:319-341) of the disordered, C-terminal domain is found to be an important driver of TDP-43 phase separation. However, a comprehensive molecular view of TDP-43 phase separation, particularly regarding the nature of heterodomain interactions, is lacking due to the challenges associated with its stability and purification. Here, we utilize all-atom and coarse-grained (CG) molecular dynamics (MD) simulations to uncover the network of interdomain interactions implicated in TDP-43 phase separation. All-atom simulations uncovered the presence of transient, interdomain interactions involving flexible linkers, RNA-recognition motif (RRM) domains and a charged segment of disordered C-terminal domain (CTD). CG simulations indicate these inter-domain interactions which affect the conformational landscape of TDP-43 in the dilute phase are also prevalent in the condensed phase. Finally, sequence and surface charge distribution analysis coupled with all-atom simulations (at high salt) confirmed that the transient interdomain contacts are predominantly electrostatic in nature. Overall, our findings from multiscale simulations lead to a greater appreciation of the complex interaction network underlying the structural landscape and phase separation of TDP-43.

Nesting statistics in the $O(n)$ loop model on random maps of arbitrary topologies

We pursue the analysis of nesting statistics in the O(n) loop model on random maps, initiated for maps with the topology of disks and cylinders by Borot, Bouttier and Duplantier (2016), here for arbitrary topologies. For this purpose, we rely on the topological recursion results by Borot, Eynard and Orantin (2011, 2015) for the enumeration of maps in the O(n) model. We characterize the generating series of maps of genus \mathsf{g} with k boundaries and k' marked points which realize a fixed nesting graph. These generating series are amenable to explicit computations in the loop model with bending energy on triangulations, and we characterize their behavior at criticality in the dense and in the dilute phase.

Removal of acid dye from wastewater by cloud point extraction and regeneration of surfactant by pH regulation

Abstract This work concerns the coacervate extraction of industrial dye, namely Acid Green 9 (AG-9) from aqueous solution by nonionic surfactant Lutensol AO7 and TX-114 (readily biodegradable). Binary water/surfactant and pseudo-binary phase diagrams were plotted. The extraction results as a function of wt% of the surfactant and temperature are expressed by: percentage of solute extracted, E%, residual concentrations of solute and surfactant in the dilute phase (X s,w and X t,w respectively) and volume fraction of coacervate at equilibrium (Фc). For each parameter, whose values are determined by a design of experiments, these results are subjected to empirical smoothing in three dimensionsusing response surface methodology (RSM). The aim of this study is to find out the best compromise between E % and Фc. Under optimal conditions, the extraction extent of AG-9 reaches 98 % and 96 % using TX-114 and Lutensol AO7, respectively. The effect of Na2SO4 and CTAB addition is also studied. Finally, the possibility of recycling the surfactant is proved.

A novel liquid-liquid phase-change solvent with upper critical solution temperature for simultaneous pretreatment and separation of lignin, cellulose and hemicellulose from lignocellulosic biomass

The compact dimensional aggregate structure and the complex chemical components of lignocellulose go against its high value utilization. The mixture of dilute hydrochloric acid and n-butanol, which had a characteristic of homogeneous phase at high temperature and phase separation at low temperature, was proposed for lignocellulosic hydrolysis and hydrolysates separation. The results showed that lignocellulose was hydrolyzed under the synergy effect of hydrochloric acid and n-butanol in homogeneous condition, and hemicellulose and lignin hydrolysates were transferred automatically into dilute hydrochloric acid phase and n-butanol phase during the phase separation of the solvent after pretreatment, respectively. N-butanol accelerated lignin hydrolysis and protected β-O-4 linkage within lignin during the pretreatment. Meanwhile, the cellulose within solid phase product from the pretreatment was of high crystallinity, and its glucose yield in enzymatic saccharification at 48 and 72 h were 73.5% and 97.3%, respectively. This study provides a new method for lignocellulose hydrolysis and hydrolysates separation, and lays a theoretical foundation for lignocellulosic utilization of all component.

Dilution Refrigeration Technology

As the main means of obtaining extremely low temperatures of 10mK, dilution refrigerators are widely used in quantum computing, condensed matter physics and other fields. The development of the most widely used typical dry dilution refrigerators has been relatively mature internationally, while there is little research on other types of dilution refrigerators, and there is a lack of comprehensive and systematic research on dilution refrigeration technology.<br>This paper focuses on the current status of dilution refrigeration technology research, introduces its basic principles, and points out that the fundamental reason for continuous refrigeration is the limited solubility of 3He in 4He and the enthalpy difference between the concentrated phase and the dilute phase. The implementation forms and research progress of typical dilution refrigerators, 4He cycle dilution refrigerators, cold cycle dilution refrigerators and space dilution refrigerators are summarized, and their respective application occasions and advantages and disadvantages are discussed. The key influencing factors and design calculation methods for realizing dilution refrigerators below 10mK are analyzed from the aspects of Kapitza thermal resistance, osmotic pressure, and resistance, providing a reference for the research of dilution refrigeration technology.

A hierarchical approach to designing a Na-rich phosphide solid-state electrolyte for Na-ion batteries

A hierarchical approach employing the concepts of dilute element compounds (DECs), phase engineering, and defect engineering for the design of a Na-rich phosphide solid-state electrolyte.

Low-Viscous, Dilute Phase Adhesive from Dense Polyphenolic Coacervates of Poly(vinyl alcohol) and Tannic acid.

This study explores a polyphenolic coacervate, named VATA, formed by poly(vinyl alcohol) (PVA) and tannic acid (TA). Distinct from conventional studies that have focused on the bottom, dense phase of coacervates, this research emphasizes the top, dilute phase, low-viscous coacervate liquid termed liquid-VATA (l-VATA). Due to TA's capability of intermolecular association as well as adhesiveness, phenomena not typically observed in the upper dilute phase of standard polyelectrolyte-based coacervates are revealed. At first glance, the dilute phase l-VATA coacervate resembles a water-like, low-viscous mixture solution of PVA, TA, and PVA/TA complexes. However, analysis shows that nearly all of the TA molecules associate with PVA chains, forming PVA/TA complexes. Furthermore, supraparticular association was observed between PVA/TA complex nanoparticles upon applying external shear force. A broad survey of shear rate and strain showed that the solution exhibited sequential shear-thickening, followed by shear-thinning behavior. The water-like, low viscosity of l-VATA unexpectedly reveals robust adhesiveness and thus able to lift an entire mouse using just a single human hair strand. Even in cases of failure, no interfacial failure was detected between mouse and human hair. In addition to enabling hair-to-hair bonding, our study also showcases the efficacy of l-VATA in facilitating hair-to-skin adhesion. The results illustrate how the lower viscosity of l-VATA can be exploited for a wide range of industrial and cosmetic applications, allowing the formulation of thin, uniform adhesive layers, something unachievable with the dense, viscous VATA glue. Thus, this study highlights the importance of investigating the top dilute phase of coacervates, shedding light on an area often underestimated compared to the bottom dense phase reported in prevalent coacervate studies.

Coupling particle image velocimetry and digital image analysis to characterize cluster dynamics in a fast fluidized bed

Particle clusters affect interphase interaction and dominate the overall performance of gas-solid fluidized beds. In this work, the particle image velocimetry, particle tracking velocimetry and digital image analysis were coupled to characterize clustering dynamics in a lab-scale riser. The clusters were identified by the Otsu algorithm based on grayscale distribution, and the cluster properties such as equivalent size, solids concentration and velocity distribution were extracted and analyzed under various operating conditions. It was found macroscopic operating conditions affect cluster characteristics significantly whereas the effect of particle composition is secondary. A bimodal or skewed probability density function was observed for not only the time-averaged hydrodynamic velocity but also the particle velocity around the cluster interface, indicating the coexistence of dilute and dense phases and the breaking of equilibrium assumption. The nonuniform distributions for laminar and Reynolds-stress-like granular temperatures were further discussed, which show remarkable anisotropy at both the microscopic and mesoscopic scales.

Ultrafast Spectroscopy Reveals Slow Water Dynamics in Biocondensates.

Cells achieve high spatiotemporal control over biochemical processes through compartmentalization to membrane-bound as well as membraneless organelles that assemble by liquid-liquid phase separation. Characterizing the balance of forces within these environments is essential to understanding their stability and function, and water is an integral part of the condensate, playing an important role in mediating electrostatic and hydrogen-bonding interactions. Here, we investigate the ultrafast, picosecond hydrogen-bond dynamics of a model biocondensate consisting of a peptide poly-l-arginine (Poly-R) and the nucleic acid adenosine monophosphate (AMP) using coherent two-dimensional infrared (2D IR) spectroscopy. We investigated three vibrational modes: the arginine side-chain C═N stretches, an AMP ring mode, and the amide backbone carbonyl stretching modes. Dynamics slow considerably between the dilute phase and the condensate phase for each vibrational probe. For example, the arginine side-chain C═N modes slow from 0.38 to 2.26 ps due to strong electrostatic interactions. All-atom molecular dynamics simulations provide an atomistic interpretation of the H-bond network disruption resulting from electrostatic contributions as well as collapse within the condensate. Simulations predict that a fraction of water molecules are highly constrained within the condensate, explaining the observed slowdown in the H-bond dynamics.

Phase separation reduces cell-to-cell variability of transcriptional bursting

Gene expression is a stochastic and noisy process often occurring in "bursts". Experiments have shown that the compartmentalization of proteins by liquid-liquid phase separation is conducive to reducing the noise of gene expression. Therefore, an important goal is to explore the role of bursts in phase separation noise reduction processes. We propose a coupled model that includes phase separation and a two-state gene expression process. Using the timescale separation method, we obtain approximate solutions for the expectation, variance, and noise strength of the dilute phase. We find that a higher burst frequency weakens the ability of noise reduction by phase separation, but as the burst size increases, this ability first increases and then decreases. This study provides a deeper understanding of phase separation to reduce noise in the stochastic gene expression with burst kinetics.

Nesting Statistics in the O(n) Loop Model on Random Planar Maps

In the O(n) loop model on random planar maps, we study the depth—in terms of the number of levels of nesting—of the loop configuration, by means of analytic combinatorics. We focus on the ‘refined’ generating series of pointed disks or cylinders, which keep track of the number of loops separating the marked point from the boundary (for disks), or the two boundaries (for cylinders). For the general O(n) loop model, we show that these generating series satisfy functional relations obtained by a modification of those satisfied by the unrefined generating series. In a more specific O(n) model where loops cross only triangles and have a bending energy, we explicitly compute the refined generating series. We analyse their non generic critical behavior in the dense and dilute phases, and obtain the large deviations function of the nesting distribution, which is expected to be universal. Using the framework of Liouville quantum gravity (LQG), we show that a rigorous functional KPZ relation can be applied to the multifractal spectrum of extreme nesting in the conformal loop ensemble (CLEκ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{CLE}_{\\kappa }$$\\end{document}) in the Euclidean unit disk, as obtained by Miller et al. (Ann Probab 44(2):1013–1052, 2016, arXiv:1401.0217), or to its natural generalisation to the Riemann sphere. It allows us to recover the large deviations results obtained for the critical O(n) random planar map models. This offers, at the refined level of large deviations theory, a rigorous check of the fundamental fact that the universal scaling limits of random planar map models as weighted by partition functions of critical statistical models are given by LQG random surfaces decorated by independent CLEs.

Interfacial Assembly of Bacterial Microcompartment Shell Proteins in Aqueous Multiphase Systems.

Compartments are a fundamental feature of life, based variously on lipid membranes, protein shells, or biopolymer phase separation. Here, this combines self-assembling bacterial microcompartment (BMC) shell proteins and liquid-liquid phase separation (LLPS) to develop new forms of compartmentalization. It is found that BMC shell proteins assemble at the liquid-liquid interfaces between either 1) the dextran-rich droplets and PEG-rich continuous phase of a poly(ethyleneglycol)(PEG)/dextran aqueous two-phase system, or 2) the polypeptide-rich coacervate droplets and continuous dilute phase of a polylysine/polyaspartate complex coacervate system. Interfacial protein assemblies in the coacervate system are sensitive to the ratio of cationic to anionic polypeptides, consistent with electrostatically-driven assembly. In both systems, interfacial protein assembly competes with aggregation, with protein concentration and polycation availability impacting coating. These two LLPS systems are then combined to form a three-phase system wherein coacervate droplets are contained within dextran-rich phase droplets. Interfacial localization of BMC hexameric shell proteins is tunable in a three-phase system by changing the polyelectrolyte charge ratio. The tens-of-micron scale BMC shell protein-coated droplets introduced here can accommodate bioactive cargo such as enzymes or RNA and represent a new synthetic cell strategy for organizing biomimetic functionality.

Eulerian investigation of the mechanism of Ultra-low NOx emissions from CFB boilers with finer bed material

Industrial practice has confirmed that decreasing the bed material size substantially diminishes nitrogen oxide (NOx) emissions in coal-fired circulating fluidized bed (CFB) boilers. This reduction allows for compliance with the stringent ultra-low emissions standard (NOx < 50 mg/Nm3@6%O₂, dry) proposed by the Chinese government, all without the need for supplementary denitrification devices. Consequently, it becomes essential to delve into the mechanisms through which particle size, as a gas–solid flow characteristic, directly affects the chemical reaction dynamics within the coal combustion process. Due to the difficulty of field tests, this paper employs the Eulerian-Eulerian numerical method suitable for wide particle size distributions to investigate the impact of bed material particle size on gas–solid flow and NOx concentration. Furthermore, the generalized QC-EMMS drag model is utilized to predict the heterogeneous flow across varying particle size conditions. Industrial test data validated the simulation accuracy, with prediction errors of bed pressure drop, temperature, and NOx emission concentration ranging from 5 % to 8.1 %. The analysis revealed that the particle concentration distribution heterogeneity decreases as the particle size diminishes. The variation trends of NOx with particle size exhibit distinct differences between the lower dense phase region and the upper dilute phase region within the bed. For finer bed material particles, the high NOx concentration generated in the dense phase region experiences a more thorough reduction in the dilute phase region. Through the analysis of material concentration and reaction rate, it is believed that this phenomenon is related to the increased catalytic effect of fine ash particles in the dilute phase region, that is, the reduction in particle size leads to an increase in catalytic specific surface area, enhancing NOx reduction, thus achieving ultra-low emissions at the outlet. These research results provide theoretical support for further development of ultra-low emission coal-fired CFB boilers.

Validation of mesoscience-based structural model for simulating gas–solid flows in circulating-turbulent fluidized beds

The circulating-turbulent fluidized bed (CTFB) is an important fluidization regime that can maintain a high solid concentration and high reaction intensity as in turbulent fluidized bed, and suppress solids back-mixing as in circulating fluidized bed. Computational fluid dynamics (CFD) studies on it are however very sparse. In this study, extensive three-dimensional CFD simulations of CTFB are carried out using the mesoscience-based structural model (Liu et al., 2023), where the gas-rich dilute phase and the particle-rich dense phase are defined as the two interpenetrating continua, instead of treating the gas and particles as the two interpenetrating continua as in classical two-fluid models. It is shown that the model is able to faithfully predict the hydrodynamics of CTFB, in terms of axial and radial solid concentration profiles and radial solid velocity profiles. This study not only provides a systematical CFD study on the hydrodynamics of gas–solid flow in CTFB but also offers validations of the mesoscience-based structural model via simulating the hydrodynamics of new fluidization regime (CTFB).

Monitoring self-discharge in a dual-ion battery using in situ Raman spectro-electrochemistry

A dual-ion battery employs two graphite electrodes to host cations and anions from the electrolyte. The high potential required to intercalate anions in graphite fully, typically > 5 V versus Li+/Li, triggers electrolyte decomposition and dissolution of the aluminium current collector. Such unwanted reactions significantly aggravate self-discharge, leading to low energy efficiency and shorter cycle life. This study investigates changes in graphite structure during the intercalation of bis(fluorosulfonyl)imide (FSI) anion in 4 M LiFSI in ethyl methyl carbonate (EMC) and evaluates the stability of the associated FSI-intercalated graphite compounds using in situ Raman spectroscopy. The results highlight the critical importance of the duration the GICs remain in contact with the electrolyte, before the acquisition of the Raman spectra. Accordingly, the GICs with high FSI anion content exhibited only short-term stability and lost anions during open-circuit potential relaxation; only dilute GIC phases (stages ≥ IV) were sufficiently stable in the presence of the concentrated electrolyte. Furthermore, the formation of gaseous products during the charge–discharge cycles was verified using a 3-electrode cell with a pressure sensor. Future studies can adopt the experimental strategy developed in this work to assess the efficacy of electrolyte additives in mitigating self-discharge in DIBs.

Conformational Properties of Polymers at Droplet Interfaces as Model Systems for Disordered Proteins.

Polymer models serve as useful tools for studying the formation and physical properties of biomolecular condensates. In recent years, the interface dividing the dense and dilute phases of condensates has been discovered to be closely related to their functionality, but the conformational preferences of the constituent proteins remain unclear. To elucidate this, we perform molecular simulations of a droplet formed by phase separation of homopolymers as a surrogate model for the prion-like low-complexity domains. By systematically analyzing the polymer conformations at different locations in the droplet, we find that the chains become compact at the droplet interface compared with the droplet interior. Further, segmental analysis revealed that the end sections of the chains are enriched at the interface to maximize conformational entropy and are more expanded than the middle sections of the chains. We find that the majority of chain segments lie tangential to the droplet surface, and only the chain ends tend to align perpendicular to the interface. These trends also hold for the natural proteins FUS LC and LAF-1 RGG, which exhibit more compact chain conformations at the interface compared to the droplet interior. Our findings provide important insights into the interfacial properties of biomolecular condensates and highlight the value of using simple polymer physics models to understand the underlying mechanisms.

Transition from a foam-like to an onion-like nanostructure in water-rich L3 phases

Abstract In dilute water-surfactant systems L3 phases are found in which bilayers interconnect to form a sample-spanning sponge-like structure. From our previous study of the system water/NaCl-AOT (sodium bis(2-ethylhexyl) sulfosuccinate) we know that a transition of this sponge-like structure to an oil-continuous foam-like structure occurs upon addition of minute amounts of oil (about 3 wt%, α = 0.03) in the L3 channel at a constant surfactant mass fraction of γ = 0.15 and T = 25 °C. The aim of the present study was to verify if the same transition occurs at γ = 0.25. To achieve this goal, we determined the relevant part of the phase diagram and studied the electrical conductivities and viscosities within the narrow one-phase L3 channel. Although the electrical conductivities and viscosities change qualitatively like those observed at γ = 0.15 we did not observe a sponge-like structure at γ = 0.25 in the oil-free system (α = 0) with freeze-fracture electron microscopy (FFEM) and freeze fracture direct imaging (FFDI). Together with the FFEM/FFDI images and SANS/SAXS curves we provide experimental evidence for a structural transition with decreasing oil content from a thermodynamically stable foam-like to a thermodynamically stable onion-like nanostructure at γ = 0.25 rather than to a sponge-like structure as is the case at γ = 0.15.

CFD-DEM Simulation of Slugging and Non-Slugging Fast Fluidization of Fine Particles in a Micro Riser

The discrete element method (DEM) coupled with computational dynamics (CFD) has been considered one of the most sensitive ways of studying the micro fluidized bed. This article proposes a so-called particle circumstance-dependent drag model that is dependent on a particle’s complex circumstances. Slugging and non-slugging fast fluidization in a micro fluidized bed is modeled with the use of the CFD-DEM. The results show that the formation and the fragmentation of clusters in a slugging fast fluidized state are clearly captured, and both have time synchronization. However, with the increase in gas velocity, the boundary of the dense and dilute phases turns blurry and the slugs disappear. Furthermore, there exists a relatively serious backmixing of particles in the slugging fast fluidization, while the backmixing effect weakens in the non-slugging fast fluidization. Moreover, the outlet solid flux decreases compared with those in the big fluidized beds for the slugging fast fluidized bed due to the micro size effect, while the micro size effect on the solid flux is not distinct for the non-slugging fast fluidized bed. Last but not least, the radial porosity with slugging exhibits a weakened core-annulus structure compared with the correlated radial porosity in the big fluidized beds. The radial porosity without slugging tends to approach the correlated core-annulus structure.

Understanding the Impacts of Molecular and Macromolecular Crowding Agents on Protein-Polymer Complex Coacervates.

Complex coacervation refers to the liquid-liquid phase separation (LLPS) process occurring between charged macromolecules. The study of complex coacervation is of great interest due to its implications in the formation of membraneless organelles (MLOs) in living cells. However, the impacts of the crowded intracellular environment on the behavior and interactions of biomolecules involved in MLO formation are not fully understood. To address this knowledge gap, we investigated the effects of crowding on a model protein-polymer complex coacervate system. Specifically, we examined the influence of sucrose as a molecular crowder and polyethylene glycol (PEG) as a macromolecular crowder. Our results reveal that the presence of crowders led to the formation of larger coacervate droplets that remained stable over a 25-day period. While sucrose had a minimal effect on the physical properties of the coacervates, PEG led to the formation of coacervates with distinct characteristics, including higher density, increased protein and polymer content, and a more compact internal structure. These differences in coacervate properties can be attributed to the effects of crowders on individual macromolecules, such as the conformation of model polymers, and nonspecific interactions among model protein molecules. Moreover, our results show that sucrose and PEG have different partition behaviors: sucrose was present in both the coacervate and dilute phases, while PEG was observed to be excluded from the coacervate phase. Collectively, our findings provide insights into the understanding of crowding effects on complex coacervation, shedding light on the formation and properties of coacervates in the context of MLOs.