Release Of Water Molecules Research Articles

Functionalized composite nanofiber membranes for selective steroid hormone micropollutants uptake from water: Role of cyclodextrin type

Cyclodextrins (CD) entrapped in nanofiber composite membranes are potential selective adsorbing materials to remove steroid hormone (SHs) micropollutants from water. This study aims to elucidate the role of CD macrocyclic host type on the SHs inclusion complexation and uptake in filtration. Three CD types (α, β, and γ) are cross-linked with epichlorohydrin to form polymers (αCDP, βCDP and γCDP) and entrapped into a nanofiber composite membrane by electrospinning. TGA analysis confirmed the CD entrapment into the nanofiber without loss of CD molecules during filtration.The CD type plays a dominant role in controlling the removal of different SHs. A similar removal (range 33 to 50 %) was observed with αCDP, irrespective of the SH type. In contrast, removal and uptake dependent on SH type were observed for β and γCDP, with the highest removal of 74 % for progesterone, followed by estradiol (46 %) and estrone (27 %) and the lowest removal of 3 % for testosterone.Molecular dynamic (MD) simulation revealed a stronger and more stable complex formed with βCDP, as demonstrated by: i) the closer spatial distribution of SH molecules from the βCDP cavity and, ii) the quantum chemistry calculations of the lower de-solvation energy (+6.0 kcal/mol), which facilitates the release of water molecules from interacting interface of CD molecule and hormone. Regarding γCDP, the highest de-solvation energy (+8.3 kcal/mol) poses an energetic barrier, which hinders the formation of the inclusion complex. In the case of αCDP, a higher interaction energy (-8.9 kcal/mol) compared to βCDP (-4.9 kcal/mol) was obtained, despite the broader spatial distribution observed from the MD simulation attributed to a dominant hydrogen bonding interaction with the OH primary groups on the external surface cavity.The findings highlight the relevance of the CD type in designing selective adsorbing membranes for steroid hormone micropollutant uptake. Experimental results and MD simulation suggest that βCD is the most suitable CD type for steroid hormone uptake, due to a more stable and stronger inclusion complexation than α and γCD.

Ions effect on tunable coacervate and its relevance to the Hofmeister series

Ion induced self-assembly allows a better understanding of the natural self-assemblies such as proteins, colloids and polymers, etc. However, little is known about ions mediated tunable coacervates. Herein, we show that the Hofmeister series of ions can be used to explain the tunable coacervates induced by different types of ions. The assembly of benzenesulfonate and polyetheramine undergoes the transformation from bilayer vesicles to the network structure of bottom coacervate with the increased concentration of inorganic salt, and the tunable coacervates of surfactants was found to be highly dependent on the ion species in solution. The affinity and compatibility of cations and surfactant follows Li+ > Na+ > K+, which determines the disturbance range of water molecules in the hydration shell of surfactant, resulting in different states of the final aggregates varying from precipitate, upper coacervate to bottom coacervate. The chaotropic anions (e.g., I−) have more pronounced dehydration effect on surfactants compared with kosmotropic anions (e.g., F−), and the ability of anions induced the transition from the bottom to the upper coacervate follows I−> Br− > Cl− >F−. Since the structural transformation of bottom coacervate requires conformational entropy, the release of water molecules is thermodynamically favorable for the transition of coacervates, which is also verified by the fact that the occurrence of dehydration drives the bottom coacervate upward to the upper coacervate during the heating process. These results provide a close link between the Hofmeister series and the controllable coacervates, which is of importance for further progress in ion specificity effects and creates a basic physicochemistry skeleton to understand this important phenomenon.

Mechanism of Peroxynitrite Interaction with Ferric M. tuberculosis Nitrobindin: A Computational Study.

Nitrobindins (Nbs) are all-β-barrel heme proteins present along the evolutionary ladder. They display a highly solvent-exposed ferric heme group with the iron atom being coordinated by the proximal His residue and a water molecule at the distal position. Ferric nitrobindins (Nb(III)) play a role in the conversion of toxic peroxynitrite (ONOO-) to harmless nitrate, with the value of the second-order rate constant being similar to those of most heme proteins. The value of the second-order rate constant of Nbs increases as the pH decreases; this suggests that Nb(III) preferentially reacts with peroxynitrous acid (ONOOH), although ONOO- is more nucleophilic. In this work, we shed light on the molecular basis of the ONOO- and ONOOH reactivity of ferric Mycobacterium tuberculosis Nb (Mt-Nb(III)) by dissecting the ligand migration toward the active site, the water molecule release, and the ligand binding process by computer simulations. Classical molecular dynamics simulations were performed by employing a steered molecular dynamics approach and the Jarzynski equality to obtain ligand migration free energy profiles for both ONOO- and ONOOH. Our results indicate that ONOO- and ONOOH migration is almost unhindered, consistent with the exposed metal center of Mt-Nb(III). To further analyze the ligand binding process, we computed potential energy profiles for the displacement of the Fe(III)-coordinated water molecule using a hybrid QM/MM scheme at the DFT level and a nudged elastic band approach. These results indicate that ONOO- exhibits a much larger barrier for ligand displacement than ONOOH, suggesting that water displacement is assisted by protonation of the leaving group by the incoming ONOOH.

Interfacial Dehydration Strategy for Chitosan Film Shape Morphing and Its Application.

Shape morphing of biopolymer materials, such as chitosan (CS) films, has great potential for applications in many fields. Traditionally, their responsive behavior has been induced by the differential water swelling through the preparation of multicomponent composites or cross-linking as deformation is not controllable in the absence of these processes. Here, we report an interfacial dehydration strategy to trigger the shape morphing of the monocomponent CS film without cross-linking. The release of water molecules is achieved by spraying the surface with a NaOH solution or organic solvents, which results in the interfacial shrinkage and deformation of the entire film. On the basis of this strategy, a range of CS actuators were developed, such as soft grippers, joint actuators, and a light switch. Combined with the geometry effect, edited deformation was also achieved from the planar CS film. This shape-morphing strategy is expected to enable the application of more biopolymers in a wide range of fields.

Responsive cellulose nanocrystal / acrylamide / poly (ethylene glycol) photonic films with chiral nematic structures by co-assembly and photopolymerization

Cellulose nanocrystals (CNCs), acrylamide (AAm) and poly (ethylene glycol) (PEG) can be co-assembled and photopolymerized into responsive, patterned photonic films with chiral nematic (N*) structures. Here, we report stimuli-responsive CNC/AAm/ PEG composite films (CFs) for use in humidity sensing. With the increase of AAm content, the CFs had an increased helical pitch and showed a red shift. With the adding of PEG, the CFs can quickly capture or release water molecules in air, which resulted in the changes of the helical pitch in N* structures and the structural color. After photopolymerization, the elastic modulus, hardness by nanomechanical testing and tensile strength of polymer films (PFs) were improved compared with CFs. The elastic modulus and hardness of PFs increased with the increase of AAm content. PFs and CFs showed different swelling properties in solutions with different EtOH / H2O ratio. Due to the swelling properties difference between CFs and PFs, partial photopolymerized photonic film showed photonic pattern. This research provides a new method to prepare photonic films with sensitive color response to humidity and photonic pattern, which has potential applications in the fields of sensing, anti-counterfeiting, and decoration.

Entropy Tug-of-War Determines Solvent Effects in the Liquid-Liquid Phase Separation of a Globular Protein.

Liquid-liquid phase separation (LLPS) plays a key role in the compartmentalization of cells via the formation of biomolecular condensates. Here, we combined atomistic molecular dynamics (MD) simulations and terahertz (THz) spectroscopy to determine the solvent entropy contribution to the formation of condensates of the human eye lens protein γD-Crystallin. The MD simulations reveal an entropy tug-of-war between water molecules that are released from the protein droplets and those that are retained within the condensates, two categories of water molecules that were also assigned spectroscopically. A recently developed THz-calorimetry method enables quantitative comparison of the experimental and computational entropy changes of the released water molecules. The strong correlation mutually validates the two approaches and opens the way to a detailed atomic-level understanding of the different driving forces underlying the LLPS.

Dual Effect of Secondary Solutes on Binding Equilibria: Contributions from Solute-Reactant Interactions and Solute-Water Interactions.

This study examines the role of water in binding equilibria with a special focus on secondary solutes (cosolutes) that influence the equilibrium but are not constituents of the final product. Using a thermodynamic framework that includes an explicit term for the release of water molecules upon binding, this investigation reveals how solutes may alter equilibria by changing the activity of the reactants, reflected in ΔG°(obs), and by changing the chemical potential of the solvent, reflected in ΔGS. The framework is applied to four experimental binding systems that differ in the degree of electrostatic contributions. The model systems include the chelation of Ca2+ by EDTA and three host-guest reactions; the pairings of p-sulfonatocalix[4]arene with tetramethylammonium ion, cucurbit[7]uril with N-acetyl-phenylalanine-amide, and β-cyclodextrin with adamantane carboxylate are tested. Each reaction pair is examined by isothermal titration calorimetry at 25 °C in the presence of a common osmolyte, sucrose, and a common chaotrope, urea. Molar solutions of trehalose and phosphate were also tested with selected models. In general, cosolutes that enhance binding tend to reduce the solvation free energy penalty and cosolutes that weaken binding tend to increase the solvation free energy penalty. Notably, the nonpolar-nonpolar interaction between adamantane carboxylate and β-cyclodextrin is characterized by a ΔGS value near zero. The results with β-cyclodextrin, in particular, prompt further discussions of the hydrophobic effect and the biocompatible properties of trehalose. Other investigators are encouraged to test and refine the approach taken here to further our understanding of solvent effects on molecular recognition.

Molecular recognition of synthetic RNAs by phenothiazinium dyes methylene blue and new methylene blue: Thermodynamic approach

Many biological process and function centers around recognition of double stranded RNA as it impacts numerous pathways associated with maturation of cellular RNA. This work assembles an intricate thermodynamic profiling of the phenothaizinium dyes methylene blue and new methylene blue with three double stranded ribonucleic acids, poly(A).poly(U), poly(C).poly(G) and poly(I).poly(C) with aid of thermal helix melting, isothermal titration calorimetry and differential scanning calorimetry experiments. Isothermal titration calorimetry had put forward that highest binding affinity was observed for poly(A).poly(U)-dye binding while the order varied as poly(A).poly(U) > poly(C).poly(G) > poly(I).poly(C). Strong stability of the polynucleotides against heat strand separation characterises the binding. Non-electrostatic component had larger share in parsing of the standard molar Gibbs energy of the binding. The processes' negative change in heat capacity is evidence of how essential hydrophobic forces are. Release of water molecules which are in random orientation mode occurs from RNA's hydrophobic binding pockets. Negative enthalpy and positive entropic change are the two significant features in this hydrophobic binding scenario. Another vital result of enthalpy-entropy compensation has been identified with the binding processes. The findings bear direct and ubiquitous acknowledgement in revitalizing our interest and broadening our horizon towards successful targeting of small molecules to RNAs.

Host–guest interactions of Crizotinib with natural and modified cyclodextrins: a combined molecular docking and molecular dynamics simulation approaches

ABSTRACT In this work, molecular docking and molecular dynamics (MD) simulation were applied to investigate the ability of natural cyclodextrins (CDs; Alpha, Beta and Gamma Cyclodextrins) and modified CDs (hydroxypropyl, random methyl and amino Beta Cyclodextrins) to form the stable inclusion complexes (ICs) with Crizotinib, the oral small molecule kinase inhibitor as a chemotropic drug. Results of molecular docking and MD simulation studies demonstrated that Crizotinib forms stable ICs with all natural and modified CDs and in the presence of this drug, all six CDs become more rigid. The presence of Crizotinib and the release of water molecules result in a decrease in the number of hydrogen bonds between cyclodextrins (CDs) and solvent molecules within the encapsulated CDs, compared to the hydrogen bonds observed in free CDs. Additionally, HPBCD exhibited the strongest affinity for binding and established the highest quantity of hydrogen bonds with Crizotinib. Finally, all results of this paper demonstrated the potential of using this formulation to improve the bioavailability of the selected drug.

Understanding the sorption behavior of tri, tetra and hexavalent f cations on metal–organic framework (MOF), ZIF-67: experimental and theoretical investigation

ABSTRACT Metal–organic frameworks (MOFs) are a class of compounds with modern-age technological importance due to diverse structural topologies, porosity, and modularity. ZIF-67 has been synthesized for efficient extraction of f cations in different oxidation states (UO2 2+, Th4+ and Eu3+) from aqueous pH medium exhibiting the trend in sorption efficiency as: Kd Th(6.19 × 103) > Kd U (5.20 × 103) > Kd Eu (1.58 × 103) in accordance to their chemical potential. Langmuir isotherm was found to be predominate with sorption capacity 85.9 mg g−1, 137.4 mg g−1 and 50.6 mg g−1 for U, Th and Eu, respectively. The sorption predominantly proceeded via pseudo 2nd order rate kinetics with rate constants: k2 U ~0.089 g mg−1 min−1, k2 Th ~0.011 g mg−1 min−1 and k2 Eu ~0.04 g mg−1 min−1. The processes were found to be spontaneous as revealed from negative ΔG values; and endothermic in nature (ΔHU ~10.5 kJ mol−1; ΔHTh ~12.8 kJ mol−1; ΔHEu ~8.3 kJ mol−1). The sorption proceeded via the formation of an inner sphere complex as indicated from their enhancement in the entropy values on sorption due to the release of water molecules. The Density Functional Theory (DFT) predicted selectivity using binding energy (ZIF-67-Eu3+ ~ -60.90 eV, ZIF-67-Th4+ ~ -70.78 eV, ZIF-67-Th4+ ~ -69.52 eV) is in line with the experimental selectivity of Th4+ > UO2 2+ > Eu3+. Total density of states (TODS) and Projected density of States (PODS) were estimated in order to understand the interaction between the ZIF-67 and f cations.

The role of Trp79 in β-actin on histidine methyltransferase SETD3 catalysis.

Nτ-methylation of His73 in actin by histidine methyltransferase SETD3 plays an important role in stabilisation of actin filaments in eukaryotes. Mutations in actin and overexpression of SETD3 have been related to human diseases, including cancer. Herein, we investigated the importance of Trp79 in β-actin on productive human SETD3 catalysis. Substitution of Trp79 in β-actin peptides by its chemically diverse analogues reveals that the hydrophobic Trp79 binding pocket modulates the catalytic activity of SETD3, and that retaining a bulky and hydrophobic amino acid at the position 79 is important for efficient His73 methylation by SETD3. Molecular dynamics simulations show that the Trp79 binding pocket of SETD3 is ideally shaped to accommodate large and hydrophobic Trp79, contributing to the favourable release of water molecules upon binding. Our results demonstrate that the distant Trp79 binding site plays an important role in efficient SETD3 catalysis, contributing to the identification of new SETD3 substrates and development of chemical probes targeting the biomedically important SETD3.

Experimental and Theoretical Investigation on the Extractive Mass Transfer of Eu3+ Ions Using Novel Amide Ligands in 1-Hexyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide.

Novel amide ligands in the ionic liquid (1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) were utilized for the liquid-liquid biphasic mass transfer of Eu3+ ions from aqueous acidic waste solution. The cation exchange mechanism was found to be operative with the formation of [Eu(NO3)2L3]+ species (L = 4-chloro-N-(1-methyl-1H-pyrazol-3-yl)picolinamide). However, the presence of an inner-sphere water molecule was revealed by density functional theory (DFT) calculations. The viscosity-induced slower kinetics was evidenced during mass transfer, which was improved by increasing temperature. The process was exothermic in nature. The improvement in the kinetics of extractive mass transfer at higher temperatures is evinced by a reduction in the distribution ratio value. The spontaneity of the reaction was evidenced through the negative Gibbs free energy value, whereas the process enhances the entropy of the system, probably by releasing water molecules at least partially during complexation. The structures of bare ligands and complexes have been optimized by using DFT calculations. A high value of complexation energy, solvation energy, and associated enthalpy and free energy change reveal the efficacy in binding Eu with O and N donor atoms. In addition, natural population analysis, atoms-in-molecules analysis, and energy decomposition analysis have been employed to explore the nature of bonding existing in Eu-O and Eu-N bonds.

Performance optimization of nanometer-thin indium-tin oxide transistors by two-step air annealing

In this study, the influence of air annealing on nanometer-thin indium tin oxide (ITO) transistors was investigated. Compared with unannealed devices, the field-effect mobility and subthreshold swing of ultrathin ITO transistors with pre-annealing, post-annealing, and two-step annealing were greatly improved. Under a pre-annealing temperature at 200 °C and post-annealing temperature at 100 °C, the ultra-thin ITO transistors showed field-effect mobility of 34.2 cm2/Vs, steep subthreshold swing of 1.95 V/decade, and high Ion/Ioff ratio of 2.46 × 107. X-ray photoelectron spectroscopy revealed that the performance changes could be ascribed to the changes in the oxygen vacancies in the ITO channel under different annealing conditions. The dependence of subthreshold swing on the annealing process may be related to the absorption and release of water molecules from the ultrathin ITO surface. Overall, these results emphasize the importance of the annealing procedures for nanometer-thin ITO transistors.

The microstrain-accompanied structural phase transition from h-MoO3 to α-MoO3 investigated by in situ X-ray diffraction.

In situ X-ray diffraction indicates that the structural phase transition from h-MoO3 to α-MoO3 is a first-order transition with a phase transition temperature range of 378.5-443.1 °C. The linear coefficients of thermal expansion of h-MoO3 are strongly anisotropic, that is, αa=b = 72.87 × 10-6 K-1 and αc = -19.44 × 10-6 K-1. In the h-MoO3 phase, water molecules are located at the (0 0 0.25) site inside the MoO6 octahedra tunnel that is formed by six MoO6 corner-sharing octahedron zigzag chains. With increasing temperature, the release of water molecules from the octahedra tunnel causes the octahedra chains to shrink and the octahedra tunnel to expand. When the phase transition occurs, the anomalous expansion of the MoO6 octahedra tunnel ruptures the Mo-O2 bonds, forming individual MoO6 octahedron zigzag chains that then share corners to generate octahedron layers in the ⟨100⟩α direction. The octahedron layers are bonded by van der Waals interactions in the ⟨010⟩α direction, crystalizing into the α-MoO3 structure.

Effect of Water on the Rearrangement of Hydrogen-Bonded Structures of 4-Aminobenzoic Acid on Au(111) and Ag(111) Surfaces

Water plays a very important role in promoting the biological self-assembly process, while our understanding is limited about how water affects and reshapes the assembly structure. Herein, the water-induced assembly structures of 4-aminobenzoic acid (PABA) on Au(111) and Ag(111) are investigated by scanning tunneling microscopy and density functional theory calculations. Water molecules could break the weak-hydrogen-bonded Kagomé structure on Au(111) and the consequent four-leaf clover structure formed by intermediate hydrogen bonds between the functional groups of PABA molecules and spontaneous release of water molecules. Upon water exposure, the four-leaf clover structure remains intact on the Au(111) surface, while the water molecules can break selectively the weak hydrogen bonds connecting the four-leaf clovers on Ag(111) and form preferential hydrogen bonds with the functional groups of PABA molecules, resulting in the generation of the water-involved structure. The adsorption energy of this hydrated structure on Ag(111) is significantly lower than that on Au(111), which may be the reason that the water-involved structure only appears on Ag(111). The result provides the real-space evidence of the interaction between water and organofunctional groups related to the type of the metal surface.

Introducing NMR strategies to define water molecules that drive metal binding in a transcriptional regulator

Staphylococcus aureus CzrA is a paradigmatic member of the ArsR family of transcriptional metalloregulators, which are critical for the bacterial response to stress. Zinc binding to CzrA, which induces DNA derepression, is entropically driven, as shown by calorimetry. A detailed equilibrium dynamics study of different allosteric states of CzrA revealed that zinc induces an entropy redistribution that controls for DNA binding regulation; however, this change in conformational entropy only accounts for a small net contribution to the total entropy. This difference between the change in conformational entropy vs. total entropy of zinc binding implies a significant contribution of solvent molecule rearrangements to this equilibrium. However, the absence of major structural changes suggests that solvent rearrangements occur mainly on the protein surface and/or from zinc desolvation, concomitant with a dynamical redistribution of conformational entropy. Previous results also suggest that zinc binding not only leads to a redistribution of protein internal dynamics, but also release of water molecules from the protein surface. In turn, these water molecules may make a significant contribution to the allosteric response that results in dissociation from the DNA.Quantifying the differential hydration of two conformational states that share very similar crystal structures and then correlating this with the protein's solvent entropy change constitutes an unresolved problem, even when thermodynamics suggest a significant contribution of solvent entropy. Here, we present different avenues to dissect hydration dynamics in a metal-binding transcriptional regulator that provide different insights into this complex problem. We explore primary solution NMR tools for probing protein–water interactions: the laboratory frame nuclear Overhauser effect (NOE) and its rotating frame counterpart (ROE) between long-lived water molecules and the protein residues. The wNOE/wROE ratio is a promising tool for the detection of hydration dynamics near the surface of a protein in a site-specific manner, minimizing contamination from bulk solvent. Molecular dynamics simulations and computational methods designed to provide a spatially resolved picture of solvent thermodynamics were also employed to provide a more complete panorama of solvent redistribution.

Dehydroxylation of smectites from Nudged Elastic Band and Born-Oppenheimer Molecular Dynamics simulations

High–temperature treatment of smectite minerals leads to the dehydroxylation process. One of the consequences of this process is the loss of sorption ability, which is an interesting, but not fully understood, phenomenon. A combination of static and dynamic quantum–chemical methods was used to analyze structural changes associated with the dehydroxylation of smectite layers. The work aims in the determination of multi–path reaction mechanism. The Nudged Elastic Band (NEB) method allowed for the recognition of intermediate structures, transition states and activation energies in the studied reaction mechanisms. Born–Oppenheimer Molecular Dynamics (BOMD) was used to investigate the interatomic distances time–evolution of atoms involved in the dehydroxylation process at different temperatures. The simulations were carried out in the crystalline phase, for which the computational model was prepared based on the dioctahedral structure of smectites with the chemical formula: Ca2+Al4Si8O22(OH)2. It was found, that the process requires a proton transfer to the oxygen atom of the hydroxyl group located in the octahedral sheet, which results in the release of water molecule from the layer. In addition, it has been shown that the process of a water molecule formation on the surface is also possible. The process occurring inside the layer is more energetically favoured than that on the surface. However, high activation energies were obtained in both cases, what proves that the dehydroxylation reaction takes place only at a relatively high temperatures. It has also been demonstrated that this process can follow several different mechanisms.

The nucleation of C-S-H via prenucleation clusters.

The nucleation and growth of calcium-silicate-hydrate (C-S-H) is of fundamental importance for the strength development and durability of the concrete. However, the nucleation process of C-S-H is still not fully understood. The present work investigates how C-S-H nucleates by analyzing the aqueous phase of hydrating tricalcium silicate (C3S) by applying inductively coupled plasma-optical emission spectroscopy as well as analytical ultracentrifugation. The results show that the C-S-H formation follows non-classical nucleation pathways associated with the formation of prenucleation clusters (PNCs) of two types. Those PNCs are detected with high accuracy and reproducibility and are two species of the 10 in total, from which the ions (with associated water molecules) are the majority of the species. The evaluation of the density and molar mass of the species shows that the PNCs are much larger than ions, but the nucleation of C-S-H starts with the formation of liquid precursor C-S-H (droplets) with low density and high water content. The growth of these C-S-H droplets is associated with a release of water molecules and a reduction in size. The study gives experimental data on the size, density, molecular mass, and shape and outlines possible aggregation processes of the detected species.

Light, Water, and Melatonin: The Synergistic Regulation of Phase Separation in Dementia.

The swift rise in acceptance of molecular principles defining phase separation by a broad array of scientific disciplines is shadowed by increasing discoveries linking phase separation to pathological aggregations associated with numerous neurodegenerative disorders, including Alzheimer's disease, that contribute to dementia. Phase separation is powered by multivalent macromolecular interactions. Importantly, the release of water molecules from protein hydration shells into bulk creates entropic gains that promote phase separation and the subsequent generation of insoluble cytotoxic aggregates that drive healthy brain cells into diseased states. Higher viscosity in interfacial waters and limited hydration in interiors of biomolecular condensates facilitate phase separation. Light, water, and melatonin constitute an ancient synergy that ensures adequate protein hydration to prevent aberrant phase separation. The 670 nm visible red wavelength found in sunlight and employed in photobiomodulation reduces interfacial and mitochondrial matrix viscosity to enhance ATP production via increasing ATP synthase motor efficiency. Melatonin is a potent antioxidant that lowers viscosity to increase ATP by scavenging excess reactive oxygen species and free radicals. Reduced viscosity by light and melatonin elevates the availability of free water molecules that allow melatonin to adopt favorable conformations that enhance intrinsic features, including binding interactions with adenosine that reinforces the adenosine moiety effect of ATP responsible for preventing water removal that causes hydrophobic collapse and aggregation in phase separation. Precise recalibration of interspecies melatonin dosages that account for differences in metabolic rates and bioavailability will ensure the efficacious reinstatement of the once-powerful ancient synergy between light, water, and melatonin in a modern world.

PVDF ultrafiltration membrane with enhanced mechanical and filtration performance by hydrophilic pH-response nanofibers modification

Membrane separation is an efficient strategy to disrupt the spread of pathogens in an aqueous solution and produce clean water, but its performance is seriously affected by fouling caused by bioadhesive. In this study, novel pH-response attapulgite (p-ATP) nanofibers were prepared and applied in the modification of poly(vinylidene fluoride) (PVDF) ultrafiltration membrane for bovine serum albumin (BSA) solution purification. Poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) was grafted onto the surface of attapulgite (ATP) to offer pH-response property and to improve compatibility with PVDF. p-ATP is a hydrophilic material, which can increase the anti-biofouling performance of PVDF, and its one-dimensional structure is beneficial for enhancing the inter-entanglement with organic chains in the membrane matrix. The resultant composite membrane loaded with 7% p-ATP presented 77.2% and 108.1% increase in stationary permeance and mechanical strength, respectively, than that of the pristine PVDF membrane. Furthermore, the PDMAEMA chains in p-ATP will be shrunken or swollen with the change of pH value, resulting in adsorbing or releasing water molecules. This process is effective to mitigate the adhesion between biofoulants and membrane and can break the already formed biofouling layer. So, the composite membranes are easily to be cleaned via a simple pH-change cleaning process. The molecular dynamic simulation was also conducted to analyze the high performance of the PVDF/p-ATP membrane to provide theoretical support.