Lipidation alters the phase-separation of resilin-like polypeptides.

Biology exploits biomacromolecular phase separation to form condensates, known as membraneless organelles. Despite significant advancements in deciphering sequence determinants for phase separation, modulating these features in vivo remains challenging. A promising approach inspired by biology is to use post-translational modifications (PTMs)-to modulate the amino acid physicochemistry instead of altering protein sequences-to control the formation and characteristics of condensates. However, despite the identification of more than 300 types of PTMs, the detailed understanding of how they influence the formation and material properties of protein condensates remains incomplete. In this study, we investigated how modification with myristoyl lipid alters the formation and characteristics of the resilin-like polypeptide (RLP) condensates, a prototypical disordered protein with upper critical solution temperature (UCST) phase behaviour. Using turbidimetry, dynamic light scattering, confocal and electron microscopy, we demonstrated that lipidation-in synergy with the sequence of the lipidation site-significantly influences RLPs' thermodynamic propensity for phase separation and their condensate properties. Molecular simulations suggested these effects result from an expanded hydrophobic region created by the interaction between the lipid and lipidation site rather than changes in peptide rigidity. These findings emphasize the role of "sequence context" in modifying the properties of PTMs, suggesting that variations in lipidation sequences could be strategically used to fine-tune the effect of these motifs. Our study advances understanding of lipidation's impact on UCST phase behaviour, relevant to proteins critical in biological processes and diseases, and opens avenues for designing lipidated resilins for biomedical applications like heat-mediated drug elution.

Cell deformability drives fluid-to-fluid phase transition in active cell monolayers.

Cell deformability is an essential determinant for tissue-scale mechanical nature, such as fluidity and rigidity, and is thus crucial for tissue homeostasis and stable developmental processes. However, large-scale simulations of deformable cells have been restricted to those of polygonal-shaped cells, limiting our understanding of populations of arbitrarily deformable cells, such as mesenchymal, amoeboid cells, and nonconfluent epithelial cells. Here, we present an efficient approach for simulating large populations of nonpolygonally deformable cells with considerably higher computational efficiency than existing methods. Using the method, we demonstrate that the densely packed active cell population interacting via excluded volume interactions exhibits a fluid-to-fluid transition. An experimentally measurable index of topological defects, defined using the number of neighboring cells, is also proposed to characterize this transition. This study provides a flexible approach to tissue-scale cell population and a broader perspective on the biological fluid phases.

Short-range correlation of stress chains near solid-to-liquid transition in active monolayers.

Using a three-dimensional model of cell monolayers, we study the spatial organization of active stress chains as the monolayer transitions from a solid to a liquid state. The critical exponents that characterize this transition map the isotropic stress percolation onto the two-dimensional random percolation universality class, suggesting short-range stress correlations near this transition. This mapping is achieved via two distinct, independent pathways: (i) cell-cell adhesion and (ii) active traction forces. We unify our findings by linking the nature of this transition to high-stress fluctuations, distinctly linked to each pathway. The results elevate the importance of the transmission of mechanical information in dense active matter and provide a new context for understanding the non-equilibrium statistical physics of phase transition in active systems.

Protein G-quadruplex interactions and their effects on phase transitions and protein aggregation.

The SERF family of proteins were originally discovered for their ability to accelerate amyloid formation. Znf706 is an uncharacterized protein whose N-terminus is homologous to SERF proteins. We show here that human Znf706 can promote protein aggregation and amyloid formation. Unexpectedly, Znf706 specifically interacts with stable, non-canonical nucleic acid structures known as G-quadruplexes. G-quadruplexes can affect gene regulation and suppress protein aggregation; however, it is unknown if and how these two activities are linked. We find Znf706 binds preferentially to parallel G-quadruplexes with low micromolar affinity, primarily using its N-terminus, and upon interaction, its dynamics are constrained. G-quadruplex binding suppresses Znf706's ability to promote protein aggregation. Znf706 in conjunction with G-quadruplexes therefore may play a role in regulating protein folding. RNAseq analysis shows that Znf706 depletion specifically impacts the mRNA abundance of genes that are predicted to contain high G-quadruplex density. Our studies give insight into how proteins and G-quadruplexes interact, and how these interactions affect both partners and lead to the modulation of protein aggregation and cellular mRNA levels. These observations suggest that the SERF family of proteins, in conjunction with G-quadruplexes, may have a broader role in regulating protein folding and gene expression than previously appreciated.

An aberrant fused in sarcoma liquid droplet of amyotrophic lateral sclerosis pathological variant, R495X, accelerates liquid-solid phase transition.

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.

Fragility and Tendency to Crystallization for Structurally Related Compounds.

The present study was designed to investigate the physical stability of three organic materials with similar chemical structures. The examined compounds revealed completely different crystallization tendencies in their supercooled liquid states and were classified into three distinct classes based on their tendency to crystallize. (S)-4-Benzyl-2-oxazolidinone easily crystallizes during cooling from the melt; (S)-4-Benzylthiazolidine-2-thione does not crystallize during cooling from the melt, but crystallizes easily during subsequent reheating above Tg; and (S)-4-Benzyloxazolidine-2-thione does not crystallize either during cooling from the melt or during reheating. Such different tendencies to crystallize are observed despite the very similar chemical structures of the compounds, which only differ in oxide or sulfur atoms in one of their rings. We also studied the isothermal crystallization kinetics of the materials that were shown to transform into a crystalline state. Molecular dynamics and thermal properties were thoroughly investigated using broadband dielectric spectroscopy, as well as conventional and temperature-modulated differential scanning calorimetry in the wide temperature range. It was found that all three glass formers have the same dynamic fragility (m = 93), calculated directly from dielectric structural relaxation times. This result verifies that dynamic fragility is not related to the tendency to crystallize. In addition, thermodynamic fragility predictions were also made using calorimetric data. It was found that the thermodynamic fragility evaluated based on the width of the glass transition, observed in the temperature dependence of heat capacity, correlates best with the tendency to crystallize.

Exploring the Physical Properties of Lipid Membranes with Polyhydroxy Oxanorbornane Head Group Using NBD-Conjugated and DPH Fluorescent Probes.

The present study focuses on exploring the physical properties of lipid membranes based on the polyhydroxy oxanorbornane (PH-ONB) headgroup, designed as synthetic analogues of naturally occurring archaeal lipid membranes. Specifically, we study two variants of PH-ONB headgroup-based lipids differing in the number of hydroxy groups present in the headgroup, with one having two hydroxy groups (ONB-2OH) and the other having three (ONB-3OH). These lipids form stable bilayer membranes. The study begins with a comprehensive analysis of the fluorescence characteristics of nitrobenzoxadiazole (NBD)-tagged ONB-based lipids in different solvent environments and within a model lipid membrane 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). Subsequently, the physical properties of the ONB-based membranes were examined by using an NBD-tagged ONB-based probe and a commonly used extrinsic 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescent probe. The steady-state and time-resolved fluorescence properties of the NBD-tagged ONB-based probe and DPH were used to compare the physical properties of the ONB-based membranes, including polarity, fluidity, phase transition, order, hydration, location, heterogeneity, and rotational diffusion. The solid gel to liquid crystalline phase transition temperatures of ONB-2OH and ONB-3OH lipid membranes are found to be (68 ± 1) °C and (74 ± 1) °C, respectively. The variation in organization (size), fluidity, and phase transition temperature of ONB-based lipid membranes is explained by the extent of hydrogen bonding interactions between lipid head groups. ONB-based membranes exhibit characteristics similar to those of phospholipid membranes and possess a notably high phase transition temperature. These properties make them a promising and cost-effective synthetic alternative to archaeal lipid membranes with a wide range of potential applications.

The Enrichment of Docosahexaenoic Acid from Microalgal Oil by Urea Complexation via Rotary-evaporation Crystallization.

Urea complexation is a widely used method for enriching polyunsaturated fatty acids, and cooling is the traditional approach for urea crystallization. This study aimed to investigate the potential of rotary-evaporation under vacuum as an alternative method for urea crystallization in urea complexation to enrich docosahexaenoic acid (DHA). DHA-containing microalgal oil was converted to ethyl esters (EE) as the raw material. In comparison to cooling, rotary-evaporation crystallization, as a post-treatment method for urea complexation, led to higher DHA contents in the non-urea included fractions. The ratios of urea to EE converted from DHA-containing microalgal oil was found to be the primary factors influencing urea complexation when using rotary-evaporation crystallization. Through an orthogonal test, optimal process conditions were determined, including a urea/EE ratio of 2, an ethanol/urea ratio of 7, and a rotary-evaporation temperature of 75℃. Under these conditions, a concentrate containing more than 90% DHA could be obtained.

Exploring temperature-responsive drug delivery with biocompatible fatty acids as phase change materials in ethyl cellulose nanofibers.

This study introduces a novel temperature-responsive drug delivery system using ethyl cellulose (EC) nanofibers encapsulating a eutectic mixture of lauric acid/stearic acid (LA/SA) as phase change materials (PCMs) and Rhodamine B (RhB) as a model drug. Employing blend electrospinning, the nanofibers achieved controlled drug release responsive to temperature changes. The peak shift of the carbonyl group in FTIR analysis confirmed drug-polymer compatibility, while the absence of RhB peaks in the XRD and DSC assessments revealed RhB's amorphous distribution within the fibers. Our findings demonstrate that RhB release is dependent on its loading, with a slow initial release (<2 %) for 1 % and 5 % RhB loadings and a burst release (~12 %) for 10 % loading. Notably, the release rate was tunable at 37 °C by adjusting LA/SA concentration. The optimal LA/SA loading for temperature-responsive release is identified as 10 %. Over 240 h, there is a 32 % increase in RhB release at 37 °C, and an additional 8 % increase at 40 °C, compared to 25 °C. This research illustrates the potential of PCM-integrated nanofibers in smart drug delivery, particularly for chemotherapy, antibiotics, and anti-inflammatory drugs, showcasing an innovative approach to improving therapeutic efficiency while reducing side effects.

Interfacial crystallized oleogel emulsion with improved freeze-thaw stability and tribological properties: Influence of cooling rate.

In this study, the influence of cooling rate on the freeze-thaw stability, rheological and tribological properties of interfacial crystalized oleogel emulsion was investigated. Results showed that slower cooling rate could promote formation of larger crystals and stronger network in oleogels. Additionally, oleogel emulsions showed higher freeze-thaw stability than those stabilized solely by emulsifiers. The slower cooling rate resulted in larger crystals adsorbed at the droplet surface. This led to greater steric hindrance that prevented the migration of oil droplets with higher resistance to disruption by ice crystals. The rheological and tribological measurements suggested that with appropriate amount of crystals, the tribological properties were better maintained for emulsions prepared at slow cooling rate after freeze-thaw treatment. This strategy greatly enriched oleogel emulsion formulations and provided important clues for potential applications in food products involved with freeze-thaw treatment.

Energy based techno-economic and environmental feasibility study on PV/T and PV/T heat pump system with phase change material-a numerical comparative study.

A sustainable, affordable, and eco-friendly solution has been proposed to address water heating, electricity generation, space cooling, and photovoltaic (PV) cooling requirements in scorching climates. The photovoltaic thermal system (PV/T) and the direct expansion PV/T heat pump (PV/T DXHP) were numerically studied using MATLAB. A butterfly serpentine flow collector (BSFC) and phase change material (PCM) were assimilated in the PV system and MATLAB model was developed to evaluate the economic and enviroeconomic performance of the PV/T water system (PV/T-W), PV/T PCM water system (PV/T PCM-W), the PV/T DXHP system, and the PV/T PCM heat pump system (PV/T-PCM-DXHP). In this study, annual energy production, socioeconomic factors, enviro-economic indicators, and environmental characteristics are assessed and compared. Also, an economic, environmental, and enviro-economic analysis was conducted to assess the commercial viability of the suggested system. The PV/T PCM-DXHP demonstrated the highest electrical performance of 53.69%, which is comparatively higher than the other three configurations. The discounted levelized cost of energy (DLCOE) and payback period (DPP) of the PV/T PCM-DXHP were ₹2.87 per kW-h and 3-4 years, respectively, resulting in a total savings of ₹67,7403 over its lifetime. Furthermore, installing this system mitigated 280.72 tonnes of CO2 emissions and saved the mitigation cost by ₹329,700 throughout its operational lifecycle.

Irreversible lipid phase transition detected in a porcine oocyte at chilling.

Under physiological conditions, the membranes and lipid droplets of germ cells are in a conformationally disordered phase. Typically, during cooling, lipids undergo the transition to ordered phases and, upon heating, melt into a disordered phase. In this communication, we report the lipid phase transition in lipid droplets observed in porcine oocytes. Upon cooling, a sharp lipid phase transition from conformationally disordered to ordered state was detected within the temperature range between 20 and 15 °C. Subsequent heating to 45 °C does not return lipids to their original phase state. To the best of our knowledge, this is the first observation of an irreversible phase transition in lipid droplets of biological cells with native lipid composition.

Adaptive cooling strategy via human hair: High optothermal conversion efficiency of solar radiation into thermal dissipation.

Natural species have developed complex nanostructures in a hierarchical pattern to control the absorption, reflection, or transmission of desired solar and infrared wavelengths. This bio-inspired structure is a promising method to manipulating solar energy and thermal management. In particular, human hair is used in this article to highlight the optothermal properties of bio-inspired structures. This study investigated how melanin, an effective solar absorber, and the structural morphology of aligned domains of keratin polymer chains, leading to a significant increase in solar path length, which effectively scatter and absorb solar radiation across the hair structure, as well as enhance thermal ramifications from solar absorption by fitting its radiative wavelength to atmospheric transmittance for high-yield radiative cooling with realistic human body thermal emission.

Cooling supply with a new type of evacuated solar collectors: a techno-economic optimization and analysis.

Renewable cooling via absorption chillers being supplied by various green heat technologies such as solar collectors has been widely studied in the literature, but it is still challenging to get positive economic outcomes from such systems due to the large expenses of solar thermal systems. This study offers the use of a new generation of solar collectors, so-called eccentric reflective solar collectors, for driving single-effect absorption chillers and thereby reducing the levelized cost of cooling. This article develops the most optimal design of this system (based on several different scenarios) using multi-objective optimization techniques and employs them for a case study in Brazil to assess its proficiency compared to conventional solar-driven cooling methods. For making the benchmarking analyses fair, the conventional system is also rigorously optimized in terms of design and operation features. The results show that the eccentric solar collector would enhance the cost-effectiveness by 29%. In addition, using optimally sized storage units would be necessary to get acceptable economic performance from the system, no matter which collector type is used. For the case study, at the optimal sizing and operating conditions, the levelized cost of cooling will be 124 USD/MWh and an emission level of 18.97 kgCO2/MWh.

Stability of Rapidly Crystallizing Sulfonamides Glasses by Fast Scanning Calorimetry: Crystallization Kinetics and Glass-Forming Ability.

Production and evaluation of the kinetic stability of the amorphous forms of active pharmaceutical ingredients are among the current challenges of modern pharmaceutical science. In the present work, amorphous forms of several sulfonamides were produced for the first time using Fast Scanning calorimetry. The parameters, characterizing the glass-forming ability of the compounds, i.e. the critical cooling rate of the melt and the kinetic fragility, were determined. The cold crystallization kinetics was studied using both isothermal and non-isothermal approaches. The results of the present study will contribute to the development of approaches for producing amorphous forms of rapidly crystallizing active pharmaceutical ingredients.

Germplasm of Ozark chinquapin (Castanea ozarkensis Ashe) can be cryopreserved by dormant winter buds.

Ozark chinquapin (Castanea ozarkensis Ashe) is a forest tree, endemic to the Ozark Mountain region in Eastern United States. Its nutritious nuts were consumed by Native Americans, European settlers, livestock, and wild animals and its wood was an important rot-resistant construction material. Once a significant tree in regional forest communities, the species was nearly eradicated by a chestnut blight caused by Cryphonectria parasitca (Murill) Barr fungus. Some individuals have survived as sprouts from adventitious root buds, but they rarely reach reproductive maturity. While some in situ restoration efforts are underway, the development of a viable ex situ germplasm preservation method is critical to the conservation of this important food-bearing species. Our experiment aimed to develop a cryopreservation method for C. ozarkensis dormant winter buds subjected to eight experimental treatments before desiccation, slow cooling, and storage in liquid nitrogen vapor. The highest post cryogenic viability was 91.2 % for dormant buds pretreated with 0.3 M sucrose for 16 h followed by 0.75 M sucrose for 3 h; this treatment is suggested for cryopreservation of dormant winter buds of Ozark chinquapin germplasm.

Performance enhancement of a hybrid photovoltaic/thermal system using wire coils inside the cooling tube: numerical and experimental case.

There are several strict reasons to overcome the dependence on fossil fuels and count on renewable energy sources such as solar energy. In this study, a numerical/experimental investigation on a hybrid photovoltaic/thermal system is carried out. A hybrid system would achieve higher electrical efficiency by reducing panel surface temperature, and the heat transferred could have further benefits. Using wire coils inside cooling tubes is a passive method selected in this paper to improve heat transfer. The appropriate number of wire coils was determined using numerical simulation, and then the experimental study began in real-time. Different flow rates with different pitch to diameter ratios for wire coils were considered. The results show that placing three wire coils inside the cooling tube would increase the average electrical and thermal efficiency by 2.29 and 16.87%, respectively, compared to the simple cooling mode. According to the results, if a wire coil is used in the cooling tube, a 9.42% increase in the average total efficiency based on electricity generation during a test day would appear compared to the simple cooling. A numerical method was applied again to evaluate the results of experimental tests as well as observe the phenomena in the cooling fluid path.

Impact of Processing Methods on the Physico-chemical Properties of Posaconazole Amorphous Solid Dispersions.

BACKGROUND & PURPOSE: Different methods have been exploited to generate amorphous solid dispersions (ASDs) of poorly water-soluble drugs. However, the impact of processing methods on drug stability and dissolution hasn't been studied extensively. The purpose of the current study is to investigate the impact of the two common ASD processing methods, hot-melt extrusion (HME) and spray drying, on the chemical/physical stability and supersaturation of Posaconazole (Posa) based ASDs. METHODS & RESULTS: ASDs with 25% drug loading in hydroxypropylmethylcellulose acetate succinate were prepared using HME, and two types of spray dryers, a Procept Sprayer (ASD-Procept) and a Nano Sprayer (ASD-Nano). The relative physical stability of these ASDs upon exposure to heat and crystalline API seeding followed the order: ASD-Nano > ASD-Procept ≈HME. ASD-Procept and ASD-Nano showed similar chemical stability, slightly less stable than HME under 40°C/75%RH. All three ASDs demonstrated similar supersaturation induction times, and de-supersaturation kinetics with or without crystalline seeds. CONCLUSIONS: Posa ASDs prepared via spray drying were chemically less stable compared with HME, which can be attributed to their smaller particle size and hollow structure allowing oxygen penetration. For ASD-Procept and HME, the detailed phase changes involving recrystallization of amorphous Posa and a solid-solid phase transition from Posa Form I to Form Ia during the seed-induced studies were proposed. Similar dissolution and supersaturation-precipitation kinetics of three Posa ASDs indicated that any residual nanocrystals in the bulk ASDs were not enough to induce crystallization to differentiate ASDs made by three processing methods.

Microscopic Cracks Modulate Nucleation and Solid-State Crystallization Tendency of Amorphous Celecoxib.

Drugs have been classified as fast, moderate, and poor crystallizers based on their inherent solid-state crystallization tendency. Differential scanning calorimetry-based heat-cool-heat protocol serves as a valuable tool to define the solid-state crystallization tendency. This classification helps in the development of strategies for stabilizing amorphous drugs. However, microscopic characteristics of the samples were generally overlooked during these experiments. In the present study, we evaluated the influence of microscopic cracks on the crystallization tendency of a poorly water-soluble model drug, celecoxib. Cracks developed in the temperature range of 0-10 °C during the cooling cycle triggered the subsequent crystallization of the amorphous phase. Nanoindentation study suggested minimal differences in mechanical properties between samples, although the cracked sample showed relatively inhomogeneous mechanical properties. Nuclei nourishment experiments suggested crack-assisted nucleation, which was supported by Raman data that revealed subtle changes in intermolecular interactions between cracked and uncracked samples. Celecoxib has been generally classified as class II, i.e., a drug with moderate crystallization tendency. Interestingly, classification of amorphous celecoxib may change depending on the presence or absence of cracks in the amorphous sample. Hence, subtle events such as microscopic cracks should be given due consideration while defining the solid-state crystallization tendency of drugs.

Encounter between Gyroid and Lamellae in Janus Colloidal Particles Self-Assembled by a Rod-Coil Block Copolymer.

Controlling the internal structure of block copolymer (BCP) particles has a significant influence on its functionalities. Here, a structure-controlling method is proposed to regulate the internal structure of BCP Janus colloidal particles using different surfactants. Different microphase separation processes take place in two connected halves of the Janus particles. An order-order transition between gyroid and lamellar phases is observed in polymeric colloids. The epitaxial growth during the structural transformation from gyroid to lamellar phase undergoes a two-layered rearrangement to accommodate the interdomain spacing mismatch between these two phases. This self-assembly behavior can be ascribed to the preferential wetting of BCP chains at the interface, which can change the chain conformation of different blocks. The Janus colloidal particles can further experience a reversible phase transition by restructuring the polymer particles under solvent vapor. It is anticipated that the new phase behavior found in Janus particles can not only enrich the self-assembly study of BCPs but also provide opportunities for various applications based on Janus particles with ordered structures.