Aquaporin Research Articles

Enhancing separation performance of thin film nanocomposite membranes by self-etching of polydopamine-modified calcium carbonate during interfacial polymerization process

The acid-accepting and gas-generating properties, along with the formation of extensive nanovoids, make CaCO3 nanoparticles attractive as sacrificial nanofillers for fabricating thin-film composite (TFN) nanofiltration membranes. However, challenges such as severe agglomeration and limited acid etching efficiency of the nanoparticles hinder the pursuit of superior membrane performance. In this study, the dispersion and compatibility of CaCO3 nanoparticles within the membrane matrix were improved by modifying them with a polydopamine (PDA) coating. The abundant phenolic hydroxyl groups of PDA enhanced the hydrophilicity and negative charges of membrane surface. Additionally, the PDA capsule increased the etching extent of the CaCO3 nanoparticles by improving the nanoparticle dispersion and generating additional acid, which created sufficient water channels within the polyamide layer. It was demonstrated that incorporating 45 μg/cm2 of PDA-modified CaCO3 nanoparticles doubled the water permeance to 16.7 LMH/bar, while maintaining a low molecular weight cut-off of 249 Da and achieving rejections over 90% for five types of per- and polyfluorinated substances. The PDA modification also overcame the membrane stability issue caused by the agglomerated CaCO3 nanoparticles. This study provides a novel strategy for applying properly modified self-etching nanofillers in TFN membrane development, showing great potential for water treatment applications.

Bayesian mapping of protein kinases to vasopressin-regulated phosphorylation sites in renal collecting duct.

Vasopressin controls water permeability in the renal collecting duct by regulating the water channel protein, aquaporin-2 (AQP2). Phosphoproteomic studies have identified multiple proteins that undergo phosphorylation changes in response to vasopressin. The kinases responsible for the phosphorylation of most of these sites have not been identified. Here, we use large-scale Bayesian data integration to predict the responsible kinases for 51 phosphoproteomically identified vasopressin-regulated phosphorylation sites in the renal collecting duct. To do this, we applied Bayes' rule to rank the 515 known mammalian protein kinases for each site. Bayes' rule was applied recursively to integrate each of the seven independent datasets, each time using the posterior probability vector of a given step as the prior probability vector of the next step. In total, 30 of the 33 phosphorylation sites that increase with vasopressin were predicted to be phosphorylated by protein kinase A (PKA) catalytic subunit-α, consistent with prior studies implicating PKA in vasopressin signaling. Eighteen of the vasopressin-regulated phosphorylation sites were decreased in response to vasopressin and all but three of these sites were predicted to be targets of extracellular signal-regulated kinases, ERK1 and ERK2. This result implies that ERK1 and ERK2 are inhibited in response to vasopressin V2 receptor occupation, secondary to PKA activation. The six phosphorylation sites not predicted to be phosphorylated by PKA or ERK1/2 are potential targets of other protein kinases previously implicated in aquaporin-2 regulation, including cyclin-dependent kinase 18 (CDK18), calmodulin-dependent kinase 2δ (CAMK2D), AMP-activated kinase catalytic subunit-α-1 (PRKAA1) and CDC42 binding protein kinase β (CDC42BPB).NEW & NOTEWORTHY Vasopressin regulates water transport in the renal collecting duct in part through phosphorylation or dephosphorylation of proteins that regulate aquaporin-2. Prior studies have identified 51 vasopressin-regulated phosphorylation sites in 45 proteins. This study uses Bayesian data integration techniques to combine information from multiple prior proteomics and transcriptomics studies to predict the protein kinases that phosphorylate the 51 sites. Most of the regulated sites were predicted to be phosphorylated by protein kinase A or ERK1/ERK2.

Residues of neonicotinoid insecticides in artificial waterways of the Eastern Route of the South-to North water diversion project, China: Implications for environmental risks and human health

Neonicotinoids (NEOs) are ubiquitous in global surface waters. However, the occurrence of NEOs in artificial waterways is unclear. The South-to-North Water Diversion Project (SNWDP) is the largest water diversion project in the world. Water samples from the Luoma Lake to Dongping Lake section of the Eastern Route (ER)-SNWDP were collected and analyzed for eight widely used NEOs to study their spatiotemporal distribution, ecological risks, and health risks. The total NEO concentration was 9–666, 34–138, 8–126, and 7–103 ng L−1 in the water diversion channel, Luoma Lake, Nansi Lake, and Dongping Lake, respectively. The average total NEO concentration in the water diversion channel in the dry season was twice as high as it was in the wet season, due to the precipitation dilution effect. Rather than Luoma Lake, Nansi Lake and Dongping Lake showed a seasonal difference in the average total NEO concentration. NEO concentrations in the three lakes were influenced by the inputs from natural rivers and the water diversion channels under artificial regulation. The seasonal variation in NEO composition between the water diversion channel and the three lakes suggested the channel water was not the only source for NEOs in lakes. For individual NEO ecological risks, thiamethoxam, clothianidin, and imidacloprid in the two seasons would result in high chronic risks in the water diversion channel, and moderate to high risks in Nansi Lake and Luoma Lake. Thiacloprid would result in high chronic risks in Dongping Lake in the two seasons and Luoma Lake in the wet season. For the integral NEO risks, none of the lake water sites exceeded the acute ecological threshold. Health risk assessment suggested drinking water obtained from the ER-SNWDP was safe for public health. The health risks for children exposed to NEOs from the water intake and dermal intake were higher than that for adults.

Differential microbiome features in lake-river systems of Taihu basin in response to water flow disturbance.

In riverine ecosystems, dynamic interplay between hydrological conditions, such as flow rate, water level, and rainfall, significantly shape the structure and function of bacterial and microeukaryotic communities, with consequences for biogeochemical cycles and ecological stability. Lake Taihu, one of China's largest freshwater lakes, frequently experiences cyanobacterial blooms primarily driven by nutrient over-enrichment and hydrological changes, posing severe threats to water quality, aquatic life, and surrounding human populations. This study explored how varying water flow disturbances influence microbial diversity and community assembly within the interconnected river-lake systems of the East and South of Lake Taihu (ET&ST). The Taipu River in the ET region accounts for nearly one-third of Lake Taihu's outflow, while the ST region includes the Changdougang and Xiaomeigang rivers, which act as inflow rivers. These two rivers not only channel water into Lake Taihu but can also cause the backflow of lake water into the rivers, creating distinct river-lake systems subjected to different intensities of water flow disturbances. Utilizing high-throughput sequencing, we selected 22 sampling sites in the ET and ST interconnected river-lake systems and conducted seasonally assessments of bacterial and microeukaryotic community dynamics. We then compared differences in microbial diversity, community assembly, and co-occurrence networks between the two regions under varying hydrological regimes. This study demonstrated that water flow intensity and temperature disturbances significantly influenced diversity, community structure, community assembly, ecological niches, and coexistence networks of bacterial and eukaryotic microbes. In the ET region, where water flow disturbances were stronger, microbial richness significantly increased, and phylogenetic relationships were closer, yet variations in community structure were greater than in the ST region, which experienced milder water flow disturbances. Additionally, migration and dispersal rates of microbes in the ET region, along with the impact of dispersal limitations, were significantly higher than in the ST region. High flow disturbances notably reduced microbial niche width and overlap, decreasing the complexity and stability of microbial coexistence networks. Moreover, path analysis indicated that microeukaryotic communities exhibited a stronger response to water flow disturbances than bacterial communities. Our findings underscore the critical need to consider the effects of hydrological disturbance on microbial diversity, community assembly, and coexistence networks when developing strategies to manage and protect river-lake ecosystems, particularly in efforts to control cyanobacterial blooms in Lake Taihu.

Enhancement of heat dissipation efficiency in the CSNS target through the innovative design of a serial cooling water channel

This paper presents a coupling of the Monte Carlo method with computational fluid dynamics (CFD) to analyze the flow channel design of an irradiated target through numerical simulations. A novel series flow channel configuration is proposed, which effectively facilitates the removal of heat generated by high-power irradiation from the target without necessitating an increase in the cooling water flow rate. The research assesses the performance of both parallel and serial cooling channels within the target, revealing that, when subjected to equivalent cooling water flow rates, the maximum temperature observed in the target employing the serial channel configuration is lower. This reduction in temperature is ascribed to the accelerated flow of cooling water within the serial channel, which subsequently elevates both the Reynolds number and the Nusselt number, leading to enhanced heat transfer efficiency. Furthermore, the maximum temperature is observed to occur further downstream, thereby circumventing areas of peak heat generation. This phenomenon arises because the cooling water traverses the target plates with the highest internal heat generation at a lower temperature when the flow channels are arranged in series, optimizing the cooling effect on these targets. However, it is crucial to note that the pressure loss associated with the serial structure is two orders of magnitude greater than that of the parallel structure, necessitating increased pump power and imposing stricter requirements on the target container and cooling water pipeline. These findings can serve as a reference for the design of the cooling channels in the target station system, particularly in light of the anticipated increase in beam power during the second phase of the China Spallation Neutron Source (CSNS Ⅱ).

Aquaporin (AQP) gene family in Buffalo and Goat: Molecular characterization and their expression analysis

Aquaporins (AQPs) are essential membrane proteins facilitating water and small solute transport across cell membranes. Mammals have approximately 13 paralogs of AQPs that may have evolved through gene duplication events. These genes are present in two separate clusters within the genome. In the present study, comprehensive 13 AQP genes (AQP0–12) were cloned and characterized in buffalo and goat. The protein coding region of AQPs in both species ranged from 729 to 990 bps, corresponding to 263–330 amino acid residues. Two important residues including NPA motifs and ar/R selectivity filter were found conserved in all AQPs, except for AQP7, 11 and 12. AQP0, 2, 4, 5, 7, 9, 12 showed tissue-restricted expression, whereas AQP1, 3, 8, and 11 exhibited ubiquitous expression across several tissues. AQP10 was identified as a pseudogene in all artiodactyls. Transcript variants were identified in buffalo and goat, where some variants of goat AQP5 and 6 lacked important motifs. Evolutionary analysis indicated positive selection at or near the NPA motifs and ar/R selectivity filter of AQP0, 3, 6, 7, and 10 that may alter its structure and function. This study is crucial for future investigations aiming to study the molecular mechanisms of AQPs in response to various physiological conditions.

The Important Role of Aquaglyceroporin 7 in Health and Disease.

Aquaporins (AQPs) are highly conserved small transmembrane proteins that facilitate the transport of water and small solutes across cell membranes. Aquaglyceroporin 7 (AQP7), a significant member of the AQP family, is widely distributed throughout the body. For years, AQP7 was predominantly recognized for its role as a small-molecule transporter, facilitating the passage of small molecular substances. However, growing studies have revealed that AQP7 is also involved in the regulation of lipid synthesis, gluconeogenesis, and energy homeostasis, and it is intimately linked to a variety of diseases, such as obesity, type 2 diabetes mellitus, cardiovascular diseases, cancer, and inflammatory bowel disease. This article presents a comprehensive overview of the structure of AQP7, its regulatory mechanisms, its vital roles in both healthy and diseased states, and potential therapeutic advancements. We hope that these studies will serve as a valuable reference for the development of future treatments and diagnostic protocols targeting AQP7.

Diagnosis Method of Failure in PEMFC Using Magnetic Fields

Proton exchange membrane fuel cells (PEMFCs) are currently used in various applications because they are compact, lightweight, and easy to start up. One of the challenges in PEMFCs is the improvement of gas diffusion. To overcome this challenge, appropriate water management in the gas diffusion layer and flow channels is necessary. Therefore, PEMFC diagnostic techniques are needed to detect flooding and plugging, which affect performance and efficiency. In this study, the magnetic field inside a PEMFC was analyzed to evaluate the changes caused by the internally generated water. Three cell types were used in the experiments: normal, channel-modified, and membrane–electrode assembly-modified cells. The results showed that the current was diverted because of the channel modification and water content, which resulted in a significant difference in the vertical magnetic field. This indicates that power generation inhibition due to flooding can be detected using vertical magnetic fields.

Diagnosis Method of Failure in PEMFC Using Magnetic Fields

Proton exchange membrane fuel cells (PEMFCs) are currently used in various applications because they are compact, lightweight, and easy to start up. One of the challenges in PEMFCs is the improvement of gas diffusion. To overcome this challenge, appropriate water management in the gas diffusion layer and flow channels is necessary. Therefore, PEMFC diagnostic techniques are needed to detect flooding and plugging, which affect performance and efficiency. In this study, the magnetic field inside a PEMFC was analyzed to evaluate the changes caused by the internally generated water. Three cell types were used in the experiments: normal, channel-modified, and membrane–electrode assembly-modified cells. The results showed that the current was diverted because of the channel modification and water content, which resulted in a significant difference in the vertical magnetic field. This indicates that power generation inhibition due to flooding can be detected using vertical magnetic fields.

Aging alters the expression of trophic factors and tight junction proteins in the mouse choroid plexus

BackgroundThe choroid plexus (CP) is an understudied tissue in the central nervous system and is primarily implicated in cerebrospinal fluid (CSF) production. CP also produces numerous neurotrophic factors (NTF) which circulate to different brain regions. Regulation of NTFs in the CP during natural aging is largely unknown. Here, we investigated the age and gender-specific transcription of NTFs along with the changes in the tight junctional proteins (TJPs) and the water channel protein Aquaporin (AQP1).MethodsMale and female mice were used for our study. Age-related transcriptional changes were analyzed using quantitative PCR at three different time points: mature adult, middle-aged, and aged. Transcriptional changes during aging were further confirmed with digital droplet PCR. Additionally, we used immunohistochemical analysis (IHC) for the evaluation of in vivo protein expression. We further investigated the cellular phenotype of these NTFS, TJP, and water channel proteins in the mouse CP by co-labeling them with the classical vascular marker, Isolectin B4, and epithelial cell marker, Plectin.ResultsAging significantly altered NTF gene expression in the CP. Brain-derived neurotrophic factor (BDNF), Midkine (MDK), VGF, Insulin-like growth factor (IGF1), IGF2, Klotho (KL), Erythropoietin (EPO), and its receptor (EPOR) were reduced in the aged CP of males and females. Vascular endothelial growth factor (VEGF) transcription was gender-specific; in males, gene expression was unchanged in the aged CP, while females showed an age-dependent reduction. Age-dependent changes in VEGF localization were evident, from vasculature to epithelial cells. IGF2 and klotho localized in the basolateral membrane of the CP and showed an age-dependent reduction in epithelial cells. Water channel protein AQP1 localized in the tip of epithelial cells and showed an age-related reduction in mRNA and protein levels. TJP’s JAM, CLAUDIN1, CLAUDIN2 and CLAUDIN5 were reduced in aged mice.ConclusionsOur study highlights transcriptional level changes in the CP during aging. The age-related transcriptional changes exhibit similarities as well as gene-specific differences in the CP of males and females. Altered transcription of the water channel protein AQP1 and TJPs could be involved in reduced CSF production during aging. Importantly, reduction in the neurotrophic factors and longevity factor Klotho can play a role in regulating brain aging.Graphical

Effects of a surface layer cross-flow and slope steepness on the rate of descent of dense water flows along a slope

The pathways and mixing in dense water overflows have been addressed in a range of numerical studies based on the DOME (Dynamics of Overflow Mixing and Entrainment) setup. These studies are motivated by overflows such as the flow of dense and cold water over the ridge between Iceland and Scotland. The main route of this water is through the Faroe-Shetland channel and further through the Faroe Bank Channel. After leaving the Faroe Bank Channel, the dense water continues along the slope along the Iceland-Faroe Ridge. Across this ridge there is also a strong flow of Atlantic water that may affect the pathway and mixing in the dense plume. In the DOME investigations, the slope steepness is assumed to be constant and there is no active background flow in the ambient water masses above the dense plume. With the situation along the Iceland-Faroe Ridge in mind, the setup from the DOME experiment is adjusted to study the effects of i) the slope profile, ii) flows crossing the slope on top of the along-slope flow of dense water, and iii) the topography near the overflow channel of dense water. It is found that the rate of descent is depending on slope steepness, and for a curved slope going from flat on top of a ridge to much steeper away from the ridge, dense water parcels near the ridge top or crest will sink slower than the faster flowing dense water further down along the slope. A cross-flow over the ridge, mimicking the flow of Atlantic water over the Iceland-Faroe Ridge, will force stronger mixing between the dense water and the ambient water above and dense water mixed up into the surface water can be allowed to flow out across the ridge. Furthermore, the dynamical situation along the slope will change and fluid parcels in the deeper part of the plume can experience a faster rate of descent. By removing a barrier in the topography downstream of the overflow channel, dense water can be steered towards the ridge and the starting point of the center of mass of the descending overflow water will be higher up on the slope.

Effect of chitosan on thermal gelling properties of pork myofibrillar protein and its mechanism.

Previous studies have demonstrated that the addition of chitosan can improve the quality and functional properties of meat products. However, the underlying mechanism remains unclear. In this study, the effect and mechanism of the addition of chitosan on the gel properties of myofibrillar protein (MP) were investigated. The results indicated that the gel strength and the water-holding capacity of MP-chitosan gel increased significantly when chitosan was added at 2.5-10 mg mL-1. Myofibrillar protein samples with 10 mg mL-1 added chitosan exhibited the highest elasticity and viscosity during gel formation and strengthening. The addition of chitosan also caused a modification in both the secondary and tertiary structure of MP, resulting in an enhanced exposure of hydrophobic and sulfhydryl groups in comparison with the control. Chitosan inhibited the conversion of immobilized water into free water and the formation of water channels during the thermal gelation process of MP. The denaturation enthalpy (ΔH) of myosin decreased as the concentration of chitosan exceeded 5 mg mL-1. The microstructure showed that the incorporation of chitosan (5-10 mg mL-1) facilitated the formation of compact and well organized MP gel networks. The addition of chitosan can enhance the functional properties of meat protein and facilitate heat-induced gelation, making it a promising ingredient for improving the quality of processed meat products. © 2024 Society of Chemical Industry.

Development and Performance Evaluation of a New Conformance Control Agent Gel.

How to effectively plug the multi-scale fractured water channeling has always been the key to achieving efficient water flooding of fractured low-permeability oil reservoirs. In this paper, a new type of supramolecular-polymer composite gel is developed, which is suitable for plugging multi-scale fractured water channeling. The supramolecular-polymer composite gel is composed of a polymer (such as polyacrylamide), cross-linking agent (such as polyethyleneimine), supramolecular gel factor (such as cyclodextrin) and polarity regulator (such as ethyl alcohol). The mass fraction of polyacrylamide, polyethyleneimine, cyclodextrin and ethyl alcohol are 0.15%, 0.2%, 1% and 0.2%, respectively. At the initial state, the viscosity of the composite gelant system is less than 20 mPa·s. It has good injection performance in micro-scale fractures and can enter the deep part of a fractured reservoir. At 40 °C, the composite gelant system can form a gel with a double network structure after gelation. One of the networks is formed by the covalent interaction between polyacrylamide and polyethyleneimine, the other network is formed by the self-assembly of cyclodextrins under the action of the ethyl alcohol. The comprehensive performance of the composite gel is greatly improved. The strength of the composite gel is >5 × 104 mPa·s, and it has good plugging strength in large-scale fractures. The composite gel can be used as a conformance control agent for fractured low-permeability oilfields.

Counterion Blockade in a Heterogeneously Charged Single-File Water Channel.

The Possion-Nernst-Planck theories fail to describe the ionic transport in Angstrom channels, where conduction deviates from Ohm's law, which is attributed to the dehydration/self-energy barrier and dissociation of Bjerrum ion pairs in previous work. Here, we find that the cations can be strongly bound to the surface charge, which blocks the ionic transport in a single-file water channel, causing nonlinear current-voltage curves. The presence of free ions significantly increases the probability of bound ions being released, resulting in an ionic current. We find that ionic conduction gradually becomes Ohmic as the surface charge density increases, but the conduction amplitude decreases due to the increased friction from the bound ions. We rationalize the ionic transport using 1D Kramers' escape theory framework, which describes nonlinear ionic current and the impact of surface charge density on the I-V curves. Our results show that the strong Coulomb interaction between the counterion and surface charge may cause ionic blockade in Angstrom channels.

Permeation mechanisms of hydrogen peroxide and water through Plasma Membrane Intrinsic Protein aquaporins.

Hydrogen peroxide (H2O2) transport by aquaporins (AQP) is a critical feature for cellular redox signaling. However, the H2O2 permeation mechanism through these channels remains poorly understood. Through functional assays, two Plasma membrane Intrinsic Protein (PIP) AQP from Medicago truncatula, MtPIP2;2 and MtPIP2;3 have been identified as pH-gated channels capable of facilitating the permeation of both water (H2O) and H2O2. Employing a combination of unbiased and enhanced sampling molecular dynamics simulations, we investigated the key barriers and translocation mechanisms governing H2O2 permeation through these AQP in both open and closed conformational states. Our findings reveal that both H2O and H2O2 encounter their primary permeation barrier within the selectivity filter (SF) region of MtPIP2;3. In addition to the SF barrier, a second energetic barrier at the NPA (asparagine-proline-alanine) region that is more restrictive for the passage of H2O2 than for H2O, was found. This behavior can be attributed to a dissimilar geometric arrangement and hydrogen bonding profile between both molecules in this area. Collectively, these findings suggest mechanistic heterogeneity in H2O and H2O2 permeation through PIPs.

Experimental study on enhancing the performance of hydrokinetic integrated Darrieus-Savonius rotor in open water-channel

The kinetic energy stored in water streams could be used to generate electricity via hydrokinetic rotors, due to the availability of kinetic energy from flowing water. Darrieus and Savonius are vertical axis kinetic rotors, they are promising for generating power in low speed flows. The integrated Darrieus- Savonius hydrokinetic rotor works on the principles of integrated forces including lift and drag forces. An experimental investigation has been conducted to get the optimum configuration for Darrieus-Savonius integrated rotor in order to attain improved self-starting and high-power-factor in open channel water flow, under different inflow conditions. This study investigated the effects of the radius ratio, add-on angle, water heights, and flow velocity on performance of hydrokinetic integrated Darrieus-Savonius rotor with three standard NACA 020 airfoil shape as Darrieus rotor and single/double stage semi-circular blades as Savonius rotor on the power factor. Three radius ratios (R.R) namely (0.8, 0.6 and 0.4) and add-on angles of (0o, 30o, 45o, 60o and 90o) were studied. The experimental channel was (26 m) long water flume with a (1m wide ×1.2 m depth). The horizontal walls of the flume were made of glass with a strengthened frame, to permit visual examination. The flume entrance consisted of a receiving tank (3 m long, 1.5 m wide, and 0.75 m depth), a honeycomb pattern pipe box, and a screen box field with a large stone to dissipate the water turbulence and energy at the entrance. Two centrifugal pumps were used to supply water to the channel. Darrieus-Savonius integrated rotor was placed at distance equal to ten times width of the experimental channel, to avoid any turbulence and to make sure that the flow was steady.Based on the experimental results, it was observed that the optimum Cp values at λ (1.84), add-on angle of (45o) and R.R (0.4, 0.6 and 0.8) were (0.335, 0.29 and 0.299) respectively. The maximum hybrid performance was attained at R.R (0.4), add-on angle (45o) and tip-speed ratio (1.8) and Re (240x106) with value of (0.339). Decrease in the Re values by 25 % enhanced the performance by 1.19 %. Accordingly, it is not necessary to rely on Re values in calculating the power-factor values compared to the influence of the rest of the variables.

Genome-Wide Analysis of Aquaporins Gene Family in Populus euphratica and Its Expression Patterns in Response to Drought, Salt Stress, and Phytohormones.

Aquaporins (AQPs) play an essential role in membrane water transport during plant responses to water stresses centered on conventional upstream signals. Phytohormones (PHs) regulate plant growth and yield, working with transcription factors to help plants withstand environmental challenges and regulate physiological and chemical processes. The AQP gene family is important, so researchers have studied its function and regulatory system in numerous species. Yet, there is a critical gap the understanding of many of their molecular features, thus our full knowledge of AQPs is far-off. In this study, we undertook a broad examination of the AQP family gene in Populus euphratica via bioinformatics tools and analyzed the expression patterns of certain members in response to drought, salt, and hormone stress. A total of 22 AQP genes were examined in P. euphratica, and were categorized into four main groups, including TIPs, PIPs, SIPs, and NIPs based on phylogenetic analysis. Comparable exon-intron gene structures were found by gene structure examination, and similarities in motif number and pattern within the same subgroup was determined by motif analysis. The PeuAQP gene family has numerous duplications, and there is a distinct disparity in how the members of the PeuAQP family react to post-translational modifications. Abiotic stress and hormone responses may be mediated by AQPs, as indicated by the abundance of stress response elements found in 22 AQP genes, as revealed by the promoter's cis-elements prediction. Expression pattern analysis reveals that selected six AQP genes from the PIP subgroup were all expressed in the leaves, stem, and roots with varying expression levels. Moreover, qRT-PCR analysis discovered that the majority of the selected AQP members were up- or down-regulated in response to hormone treatment and abiotic stress. Remarkably, PeuAQP14 and PeuAQP15 appeared to be highly responsive to drought stress and PeuAQP15 exhibited a high response to salt stress. The foliar application of the phytohormones (SA, IAA, GA3, MeJA, and ABA) were found to either activate or inhibit PeuAQP, suggesting that they may mitigate the effects of water shortage of poplar water stress. The present work enhances our knowledge of the practical roles of AQPs in stress reactions and offers fundamental information for the AQP genes in poplar species. It also highlights a direction for producing new varieties of poplar species with drought, salt, and hormone tolerance and holds substantial scientific and ecological importance, offering a potential contribution to the conservation of poplar species in arid regions.

Coupled Wall Boiling and Population Balance Model for High Void Fraction Flows Under Sub-Cooled Nucleate Boiling Regime: Model Development and Validation

Abstract The subcooled flow boiling of water in a vertical annulus channel is studied numerically at low-pressure conditions. The two-fluid model is developed with flow-regime dependent interfacial transfers for mass, momentum, and energy using the algebraic interfacial area density (AIAD) framework. A discrete population balance model is used to mechanistically determine the vapor bubble diameter in the flow channel by considering the bubble aggregation and breakup effects. Energy balance at the heated wall for the subcooled nucleate boiling is handled using a suitable wall boiling model. A coupling is achieved between the discrete population balance and the wall boiling model for the nucleation and the growth rate of the vapor bubbles along the heated wall. The developed model simulates the reference experimental cases of flow boiling in a vertical channel for various flow and thermal conditions. At low wall heat flux, the wall boiling generates vapor bubbles near the heated wall and within the bubbly flow regime. With an increase in the wall heat flux, the aggregation and evaporation cause the formation of larger bubbles, which progress toward the flow channel core region, a phase that is representative of the transitional flow regime. The model's capability to predict such flow regime transition is validated with the experimental results. The bubble aggregation is found to be dominant compared to the breakup, and thus, proper choice of the aggregation factor is important for the accurate prediction of vapor parameters for the subcooled flow boiling at low-pressure conditions.

Multiresolution molecular dynamics simulations reveal the interplay between conformational variability and functional interactions in membrane-bound cytochrome P450 2B4.

Cytochrome P450 2B4 (CYP 2B4) is one of the best-characterized CYPs and serves as a key model system for understanding the mechanisms of microsomal class II CYPs, which metabolize most known drugs. The highly flexible nature of CYP 2B4 is apparent from crystal structures that show the active site with either a wide open or a closed heme binding cavity. Here, we investigated the conformational ensemble of the full-length CYP 2B4 in a phospholipid bilayer, using multiresolution molecular dynamics (MD) simulations. Coarse-grained MD simulations revealed two predominant orientations of CYP 2B4's globular domain with respect to the bilayer. Their refinement by atomistic resolution MD showed adaptation of the enzyme's interaction with the lipid bilayer, leading to open configurations that facilitate ligand access to the heme binding cavity. CAVER analysis of enzyme tunnels, AquaDuct analysis of water routes, and Random Acceleration Molecular Dynamics simulations of ligand dissociation support the conformation-dependent passage of molecules between the active site and the protein surroundings. Furthermore, simulation of the re-entry of the inhibitor bifonazole into the open conformation of CYP 2B4 resulted in binding at a transient hydrophobic pocket within the active site cavity that may play a role in substrate binding or allosteric regulation. Together, these results show how the open conformation of CYP 2B4 facilitates the binding of substrates from and release of products to the membrane, whereas the closed conformation prolongs the residence time of substrates or inhibitors and selectively allows the passage of smaller reactants via the solvent and water channels.

Reverse Solute Diffusion Enhances Sludge Dewatering in Dead-End Forward Osmosis.

Wastewater treatment plants produce high quantities of excess sludge. However, traditional sludge dewatering technology has high energy consumption and occupies a large area. Dead-end forward osmosis (DEFO) is an efficient and energy-saving deep dewatering technology for sludge. In this study, the reverse osmosis of salt ions in the draw solution was used to change the sludge cake structure and further reduce its moisture content in cake by releasing the bound water in cell. Three salts, NaCl, KCl, and CaCl2, were added to the excess sludge feed solution to explore the roles of the reverse osmosis of draw solutes in DEFO. When the added quantities of NaCl and CaCl2 were 15 and 10 mM, respectively, the moisture content of the sludge after dewatering decreased from 98.1% to 79.7% and 67.3%, respectively. However, KCl did not improve the sludge dewatering performance because of the "high K and low Na" phenomenon in biological cells. The water flux increased significantly for the binary draw solute involving NaCl and CaCl2 compared to the single draw solute. The extracellular polymer substances in the sludge changed the structure of the filter cake to improve the formation of water channels and decrease osmosis resistance, resulting in an increase in sludge dewatering efficiency. These findings provide support for improving the sludge dewatering performance of DEFO.