Liquid Nuclear Condensates Mechanically Sense and Restructure the Genome.

Phase transitions involving biomolecular liquids are a fundamental mechanism underlying intracellular organization. In the cell nucleus, liquid-liquid phase separation of intrinsically disordered proteins (IDPs) is implicated in assembly of the nucleolus, as well as transcriptional clusters, and other nuclear bodies. However, it remains unclear whether and how physical forces associated with nucleation, growth, and wetting of liquid condensates can directly restructure chromatin. Here, we use CasDrop, a novel CRISPR-Cas9-based optogenetic technology, to show that various IDPs phase separate into liquid condensates that mechanically exclude chromatin as they grow and preferentially form in low-density, largely euchromatic regions. A minimal physical model explains how this stiffness sensitivity arises from lower mechanical energy associated with deforming softer genomic regions. Targeted genomic loci can nonetheless be mechanically pulled together through surface tension-driven coalescence. Nuclear condensates may thus function as mechano-active chromatin filters, physically pulling in targeted genomic loci while pushing out non-targeted regions of the neighboring genome. VIDEO ABSTRACT.

ALS/FTLD-Linked Mutations in FUS Glycine Residues Cause Accelerated Gelation and Reduced Interactions with Wild-Type FUS.

The RNA-binding protein fused in sarcoma (FUS) can form pathogenic inclusions in neurodegenerative diseases like amyotrophic lateral sclerosis (ALS) and frontotemporal lobar dementia (FTLD). Over 70 mutations in Fus are linked to ALS/FTLD. In patients, all Fus mutations are heterozygous, indicating that the mutant drives disease progression despite the presence of wild-type (WT) FUS. Here, we demonstrate that ALS/FTLD-linked FUS mutations in glycine (G) strikingly drive formation of droplets that do not readily interact with WT FUS, whereas arginine (R) mutants form mixed condensates with WT FUS. Remarkably, interactions between WT and G mutants are disfavored at the earliest stages of FUS nucleation. In contrast, R mutants physically interact with the WT FUS such that WT FUS recovers the mutant defects by reducing droplet size and increasing dynamic interactions with RNA. This result suggests disparate molecular mechanisms underlying ALS/FTLD pathogenesis and differing recovery potential depending on the type of mutation.

Closed-loop fluid-fluid immiscibility in binary lipid-sterol membranes.

We present two binary lipid-sterol membrane systems that exhibit fluid-fluid coexistence. Partial phase diagrams of binary mixtures of dimyristoylphosphatidylcholine with 25-hydroxyxholesterol and 27-hydroxycholesterol, determined from small-angle X-ray scattering and fluorescence microscopy studies, show closed-loop fluid-fluid immiscibility gaps, with the appearance of a single fluid phase both at higher and lower temperatures. Computer simulations suggest that this unusual phase behavior results from the ability of these oxysterol molecules to take different orientations in the membrane depending on the temperature.

Phosphorus solubility in basaltic glass: Limitations for phosphorus immobilization in glass and glass-ceramics.

The composition of sewage sludge from urban wastewater treatment plants is simulated using P-doped basalts. Electron microscopy analyses show that the solubility of P in the basaltic melt is limited by the formation of a liquid-liquid immiscibility in the form of an aluminosilicate phase and a Ca-Mg-Fe-rich phosphate phase. The rheological behavior of these compositions is influenced by both phase separation and nanocrystallization. Upon a thermal treatment, the glasses will crystallize into a mixture of inosilicates and spinel-like phases at low P contents and into Ca-Mg-Fe phosphate at high P contents. Hardness measurements yield values between 5.41 and 7.66 GPa, inside the range of commercial glasses and glass-ceramics. Leaching affects mainly unstable Mg2+-PO43- complexes.

Compositional and structural characterization of monolayers and bilayers composed of native pulmonary surfactant from wild type mice.

This work comprises a structural and dynamical study of monolayers and bilayers composed of native pulmonary surfactant from mice. Spatially resolved information was obtained using fluorescence (confocal, wide field and two photon excitation) and atomic force microscopy methods. Lipid mass spectrometry experiments were also performed in order to obtain relevant information on the lipid composition of this material. Bilayers composed of mice pulmonary surfactant showed coexistence of distinct domains at room temperature, with morphologies and lateral packing resembling the coexistence of liquid ordered (lo)/liquid disordered (ld)-like phases reported previously in porcine lung surfactant. Interestingly, the molar ratio of saturated (mostly DPPC)/non-saturated phospholipid species and cholesterol measured in the innate material corresponds with that of a DOPC/DPPC/cholesterol mixture showing lo/ld phase coexistence at a similar temperature. This suggests that at quasi-equilibrium conditions, key lipid classes in this complex biological material are still able to produce the same scaffold observed in relevant but simpler model lipid mixtures. Also, robust structural and dynamical similarities between mono- and bi-layers composed of mice pulmonary surfactant were observed when the monolayers reach a surface pressure of 30mN/m. This value is in line with theoretically predicted and recently measured surface pressures, where the monolayer-bilayer equivalence occurs in samples composed of single phospholipids. Finally, squeezed out material attached to pulmonary surfactant monolayers was observed at surface pressures near the beginning of the monolayer reversible exclusion plateau (~40mN/m). Under these conditions this material adopts elongated tubular shapes and displays ordered lateral packing as indicated by spatially resolved LAURDAN GP measurements.

Bridge evolution during the coalescence of immiscible droplets.

HYPOTHESIS: Droplet coalescence is a common phenomenon and plays an important role in many applications. When two liquid droplets are brought into contact, a liquid bridge forms and expands quickly. Different from miscible droplets, an extra immiscible interface exists throughout the coalescence of immiscible droplets and is expected to affect the evolution of the liquid bridge, which has not been investigated. We hypothesized that the liquid bridge of immiscible droplets exhibits a different growth dynamics. EXPERIMENTS: We experimentally study the coalescence dynamics of immiscible droplets. The evolution of the liquid bridge is measured and compared with miscible droplets. We also propose a theoretical model to analyze the effects of immiscibility. FINDINGS: We find that immiscibility plays different roles in the viscous-dominated and inertia-dominated regimes. In the initial viscous-dominated regime, the coalescence of immiscible droplets follows the linear evolution of the bridge radius as that of miscible droplets. However, in the later inertia-dominated regime, the coalescence of immiscible droplets is slower than that of miscible droplets due to the water-oil interface. By developing a theoretical model based on the force balance, we show that this slower motion is due to the immiscible interface and the extra interfacial tension. In addition, a modified Ohnesorge number is proposed to characterize the transition from the viscous-dominated regime to the inertia-dominated regime.

Recycling reaction and separation for FACylation of loxenatide by trade-off between miscibility and immiscibility of reactants and product in methanol solution.

The growing demand and scale of production for fatty acid chain modified (FACylated) polypeptide has sparked the interest in novel production technologies. In this study, a recycling reaction and separation process was proposed and applied to the fatty acid chain modification (FACylation) of loxenatide (LOX), which was based on the difference in solubility between reactants and FACylated product. Especially, the mixed PBS-Methanol (MeOH) solution was designed to meet the demands for FACylation of LOX as well as separation of FACylated LOX and residual modifier. In order to ensure the efficient FACylation, a mixed 10% PBS-90% MeOH (v/v) solution was chosen to provide a good miscibility for two reactants, LOX and N-tetradecylmaleimide (C14-MAL). On the other hand, the immiscibility between reactant (C14-MAL) and FACylated product (N-tetradecyl-Loxenatide (C14-LOX)) could realize the separation of C14-LOX when the MeOH concentration was less than 30% (v/v). Based on this strategy, the recycling reaction and separation process for FACylation of LOX was established by adjusting the MeOH concentration in the mixed solution. The reaction yield and recovery of C14-LOX exceeded 97% and 94%, and the excess reactant C14-MAL could be recycled with a recovery of more than 80%. Furthermore, after purification by reversed-phase chromatography, C14-LOX showed good pharmacokinetic and pharmacodynamic properties in vivo. This study will have great application prospects in industrial production of C14-LOX.

WSe2-VSe2 Alloyed Nanosheets to Enhance the Catalytic Performance of Hydrogen Evolution Reaction.

Tuning the electronic structures of transition metal dichalcogenides (TMD) is essential for their implementation in next-generation energy technologies. In this study, we synthesized composition-tuned WSe2-VSe2 (W1-xVxSe2, x = 0-1) alloyed nanosheets using a colloidal reaction. Alloying the semiconducting WSe2 with VSe2 converts the material into a metallic one, followed by a 2H-to-1T phase transition at x = 0.7. Over a wide composition range, WSe2 and VSe2 are atomically immiscible and form separate ordered domains. The miscible alloy at x = 0.1 displayed enhanced electrocatalytic activity toward the hydrogen evolution reaction (HER) in an acidic electrolyte. This trend was correlated with the d-band center via a volcano-type relationship. Spin-polarized density functional theory calculations consistently predicted the atomic immiscibility, which became more significant at the 2H-1T phase transition composition. The Gibbs free energy of H adsorption on the basal planes (Se or hole sites) and the activation barriers along the Volmer-Heyrovsky reaction pathway supported the enhanced HER performance of the alloy phase, suggesting that the dispersed V-doped structures were responsible for the best HER catalytic activity. Our study demonstrates how the atomic structure of TMD alloy nanosheets plays a crucial role in enhancing catalytic activity.

Iron-rich microstructure records of high temperature multi-component silicate melt behavior in nuclear fallout.

Above-ground nuclear explosions that interact with the surface of the earth entrain materials from the surrounding environment, influencing the resulting physical and chemical evolution of the fireball, which can affect the final chemical phase and mobility of hazardous radionuclides that are dispersed in the environment as fallout particles. The interaction of iron with a nuclear explosion is of specific interest due to the potential for iron to act as a redox buffer and because of the likelihood of significant masses of metals to be present in urban environments. We investigated fallout from a historic surface interacting nuclear explosion conducted on a steel tower and report the discovery of widespread and diverse iron-rich micro-structures preserved within the samples, including crystalline dendrites and micron-scale iron-rich spheres with liquid immiscibility textures. We assert these micro-structures reflect local redox conditions and cooling rates and can inform interpretation of high temperature events, enabling new insights into fireball condensation physics and chemistry when metals from the local environment (i.e. structural steel) are vaporized or entrained. These observations also significantly expand the availability of silicate immiscibility datasets applicable to rapidly quenched systems such as meteorite impact melt glass.

Adaptive Lipid Immiscibility and Membrane Remodeling Are Active Functional Determinants of Primary Ciliogenesis.

Lipid liquid-liquid immiscibility and its consequent lateral heterogeneity have been observed under thermodynamic equilibrium in model and native membranes. However, cholesterol-rich membrane domains, sometimes referred to as lipid rafts, are difficult to observe spatiotemporally in live cells. Despite their importance in many biological processes, robust evidence for their existence remains elusive. This is mainly due to the difficulty in simultaneously determining their chemical composition and physicochemical nature, whilst spatiotemporally resolving their nanodomain lifetime and molecular dynamics. In this study, a bespoke method based on super-resolution stimulated emission depletion (STED) microscopy and raster imaging correlation spectroscopy (RICS) is used to overcome this issue. This methodology, laser interleaved confocal RICS and STED-RICS (LICSR), enables simultaneous tracking of lipid lateral packing and dynamics at the nanoscale. Previous work indicated that, in polarized epithelial cells, the midbody remnant licenses primary cilium formation through an unidentified mechanism. LICSR shows that lipid immiscibility and its adaptive collective nanoscale self-assembly are crucial for the midbody remnant to supply condensed membranes to the centrosome for the biogenesis of the ciliary membrane. Hence, this work poses a breakthrough in the field of lipid biology by providing compelling evidence of a functional role for liquid ordered-like membranes in primary ciliogenesis.

Data on bulk rock compositions, geochemical and textural contrasts between central and marginal parts of dykes, and MELTS modeling of lamprophyre dykes in the Kola Alkaline Carbonatite Province (N Europe).

This publication is a series of datasets that accompany a manuscript on petrology of lamprophyre dykes in the Kola Alkaline Carbonatite Province (N Europe) [1]. The datasets served as the basis for interpretation of melt crystallization for lamprophyric and carbonatitic dykes in the crust, to supplement many papers devoted to mantle sources and melting parameters of these rocks based on radiogenic isotopes and trace elements. The first dataset contains bulk major and trace element compositions of the dykes in three areas, Kandalaksha, Kandaguba and Turiy Mys, along with supplementary information on sampling locations and dyke characteristics. The second dataset represents photos, major and trace element plots illustrating extreme mineralogical and textural heterogeneity and layering observed in some dykes. The photographs include field photographs, optical and electron microscopy shots for thin sections in central and marginal parts of the dykes. They should be viewed together with Harker and REE diagrams illustrating the changes from dyke margins to dyke cores. The third and fourth datasets are output tables from Ryolite-MELTS software used to model crystal fractionation of the dykes from the parental melts and various P, T, fO2, XCO2, XH2O parameters. One table shows compositions of evolved melts, while the other lists crystallizing phases.

Individually coated microneedles for co-delivery of multiple compounds with different properties.

Microneedle (MN) patches provide a simple method for delivery of drugs that might otherwise require hypodermic injection. Conventional MN patch fabrication methods typically can load only one or possibly multiple miscible agents with the same formulation on all MNs, which limits the combination and spatial distribution of drugs and formulations having different properties (such as solubility) in a single patch. In this study, we coated MNs individually instead of coating all MNs from the same formulation, making possible a patch where each individual MN is coated with different formulations and drugs. In this way, individually coated MN patches co-delivered multiple agents with different physicochemical characteristics (immiscible molecules, proteins, and nanoparticles) and in different spatial patterns in the skin. MN loading was adjusted by modifying the number of coating layers, and co-delivery of multiple agents was demonstrated in the porcine skin. We conclude that individually coating MNs enables co-delivery of multiple different compounds and formulations with needle-by-needle spatial control in the skin.

Liquidus Diagram of the Ba-Y-Cu-O System in the Vicinity of the Ba2YCu3O6+x Phase Field.

This paper describes the melting equilibria in the vicinity of the high Tc phase Ba2YCu3O6+x , including evidence for two Ba-Y-Cu-O immiscible liquids. Melting equilibria have been investigated in purified air using a combination of differential thermal analysis (DTA), thermogravimetric analysis (TGA), powder x-ray diffraction (XRD), MgO wick entrapment of liquid for analysis, scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis (EDS), and hydrogen reduction for determination of copper oxidation state. For relatively barium-rich compositions, it was necessary to prepare the starting materials under controlled atmosphere conditions using BaO. A liquidus diagram was derived from quantitative data for the melts involved in various melting reactions. In general the 1/2(Y2O3) contents of the melts participating in these equilibria were low (mole fraction <4 %). The primary phase field of Ba2YCu3O6+x occurs at a mole fraction of <2.0 % 1/2Y2O3 and lies very close along the BaO-CuO x edge, extending from a mole fraction of ≈43 % CuO to a mole fraction of ≈76 % CuO. It is divided by a liquid miscibility gap and extends on either side about this gap. The topological sequence of melting reactions associated with the liquidus is presented as a function of temperature. Implications for the growth of Ba2YCu3O6+x crystals are discussed.

Theoretical Analysis of Miscibility Gaps in the Alkali-Borates.

A thermodynamic approach based on the regular solution concept is applied to the description of miscibility gap boundaries in the alkali-borate systems. It is suggested that in each system the structural units which control the entropy of mixing are the stoichiometric compounds at the apparent limit of the alkali-rich edge of the gap, and a complex boron trioxide structure. (The former is inferred by the shape of the gap, and the latter is chosen to fit the regular mixing equation.) The same boron trioxide complex is used for all the systems analyzed. The physical implications of this analysis are discussed.

Phase Equilibria in the System Niobium Pentoxide- Boric Acid.

The phase-equilibrium diagram for the system Nb2O5-B2O3 was determined experimentally using the quenching technique and examining the samples by optical microscopy and x-ray powder diffractometry. The system contains one binary compound of approximate composition "3Nb2O5 · B2O3," which melts incongruently at about 1150 °C to H -Nb2O5 and B2O3-rich liquid. A large region of liquid immiscibility extends, at 1352 °C, from 10 mole percent Nb2O5 to 65.7 mole percent Nb2O5. The theoretically calculated extent of immiscibility is in reasonable agreement with the experimentally determined value.

Phase Equilibria in the System Niobium Pentoxide-Germanium Dioxide.

The phase equilibrium diagram for the system Nb2O5-GeO2 has been determined experimentally, using the quenching technique and examining the samples by optical microscopy and x-ray powder diffractometry. The system contains one compound, 9Nb2O5·GeO2, which melts incongruently at 1420 °C. A eutectic between this compound and GeO2 is located at about 97 mol percent GeO2 and 1090 °C. The system does not show liquid immiscibility, and it is concluded that the ionic field strength limit for two-liquid separation in the series of glass formers occurs with the Nb+5 cation.

Effect of Environment on Viscous Flow in Inorganic Oxide Glasses.

Results from viscosity and shear structural relaxation measurements conducted above the liquid-liquid phase transition of a series of immiscible inorganic oxide glasses are analyzed. A model is proposed which relates the temperature dependence of the complex modulus and viscosity to the behavior of microstructure in the glass resulting from supercritical fluctuations in composition. It is suggested that the critical microstructure induces differences in local environment in the glass which in turn cause the appearance of distributions of relaxation times. The model is formulated using elementary fluctuation theory and the resulting equations are successfully compared to the data.