Phosphate Release Research Articles

Commercial organomineral fertilizer produced through granulation of a blend of monoammonium phosphate and pulp and paper industry waste post-composting

This study investigates a commercial granular organomineral fertilizer (GOF) produced by physically mixing landfill paper and cellulose industry waste composted over a long period with monoammonium phosphate (MAP), focusing on its morphological properties, and phosphate release into the water. The organic base used in the GOF composition is rich in humic and fulvic acids due to its long-term composting, rebalances the soil's organic matter, and eliminates a critical environmental liability. No studies have involved long-term lignocellulosic waste composting as the organic base of organomineral fertilizers. Most GOF and MAP granules range from 2 to 4 mm in size, with rough and macroporous surfaces observed through scanning electron microscopy. The specific surface area values of fertilizers are low compared to other fertilizers with different organic matrices. However, 2–4 mm granules exhibit similar values, indicating uniformity of granules. Infrared spectroscopy reveals bands from mineral and organic bases, with possible clay additives confirmed by the silicon detected in Energy Dispersive Spectroscopy analysis. Thermogravimetric curves exhibit improved thermal stability for GOF over the composted organic base, with a 31 °C increase in the second decomposition stage and delayed completion of the subsequent stages. However, this did not significantly alter the Tonset of the ammonium phosphate decomposition, as GOF presented a similar thermal behavior to MAP. GOF and MAP exhibit similar kinetic profiles, with rapid phosphorus release in the first 4 hours, reaching about 77 % of the available phosphorus. GOF shows an increase in specific surface area 29 times after 240 hours of contact with water, facilitating phosphorus release from the commercial mixture. MAP and GOF exhibit a release rate exceeding 84 %, indicating rapid phosphate availability. These values are comparable to those of other organomineral fertilizers. The results demonstrate that the GOF performs similarly to MAP, with lower phosphorus dosages, rebalance of soil organic matter, and increased nutrient application efficiency.

Enhanced biodegradation of glyphosate by Chlorella sorokiniana engineered with exogenous purple acid phosphatase

Organophosphate pesticides, particularly glyphosate, persist in aquatic environments due to widespread agricultural usage, posing substantial environmental and health risks. This study explores the bioremediation potential of genetically engineered Chlorella sorokiniana, expressing purple acid phosphatase (PAP) from Phaeodactylum tricornutum, for glyphosate biodegradation. The engineered strain (OE line) demonstrated complete glyphosate biodegradation at concentrations below 10 ppm within 4–6 days, surpassing the wild type (WT). Enhanced biodegradation in the OE line was attributed to increased growth and ATP levels due to the release of inorganic phosphate, indicating enhanced metabolic efficiency. Photosynthetic parameters, as well as chlorophyll, and carotenoid contents, were significantly improved, driving higher biomass accumulation. Metabolic shifts toward lipogenesis were observed, supported by the upregulation of triacylglycerol-related genes. Additionally, antioxidant enzyme activities (GPx, SOD, CAT) were elevated in the OE line, mitigating oxidative stress. Importantly, the overexpression of PAP activated and upregulated the level of endogenous CsPAP18, which displayed stable binding with glyphosate and its metabolite aminomethylphosphonic acid, highlighting the synergistic role of PAP and CsPAP18 in glyphosate biodegradation. The OE line effectively treated glyphosate-contaminated real wastewater, confirming the feasibility of engineered strain for environmental remediation. This study provides valuable insights into the potential of engineered microalgae for effective and sustainable wastewater treatment, specifically targeting the removal of organophosphate contaminants in freshwater environments.

All-Natural Ceramic Whitlockite/Wollastonite Fiber Composite Bone Scaffolds: DLP Additive Manufacturing, Microstructure, and Performance

In this study, we introduced a novel approach by using natural calcium phosphate-based ceramic whitlockite as the matrix, natural silicon-based ceramic wollastonite fiber as the secondary phase, and desktop-level DLP 3D printing as the fabrication method to develop an all-natural ceramic porous bone scaffold with excellent mechanical, degradable, biomineralization, and cell responses. The results demonstrated that, at a solid loading of 75 wt% and a sintering temperature of 1000°C, the compressive strength of the whitlockite porous scaffold reached 20.0 MPa. With the incorporation of wollastonite fiber, the compressive strength of the composite ceramic scaffold further increased to 31.0 MPa, achieving a top-tier level for desktop-level DLP-printed porous ceramic bone scaffolds. This mechanical enhancement effect was mainly attributed to the grain refinement effect of WF on whitlockite and the fiber reinforcement effect of WF. Additionally, the degradation rate of the composite ceramic scaffold increased with higher WF content, attributed to the rapid degradation rate of WF and the microstructural changes in the whitlockite matrix induced by WF doping. Furthermore, the biomineralization capability and cellular response of the composite ceramic scaffold were enhanced with WF doping, due to the improved degradation ability promoting the release of calcium, phosphate, and silicon ions. This study further validates the applicability of desktop-level DLP for fabricating ceramic bone scaffolds and provides evidence of the potential of all-natural ceramic whitlockite/WF as bone scaffold materials.

Preparation and characterization of a novel active sediment capping material (geopolymer) for inhibiting phosphate releasing from sediment

In situ remediation of sediment can effectively control the release of phosphate in sediment and improve water eutrophication. The essential question of this remediation techniques lies in the development of stable, high-efficiency, low-cost and easily available active sediment capping materials. This study synthesised a novel sediment capping material using bulk solid waste, and phosphate inhibition mechanism of the materials was explored. Results indicated that GSCM was prepared under the conditions of NaOH concentration of 3M, hydrothermal temperature of 160℃, hydrothermal time of 36h and the mass ratio of 40wt.% SS to 60wt.% FA. The result of batch adsorption and compressive strength test suggested that phosphate adsorption capacity and compressive strength of GSCM were 2.15mg/g and 24.20MPa, respectively. The characterization result showed that GSCM was composed of sodium zeolite, riversideite, grossular and fayalite, exhibiting a uniformly distributed slit mesoporous structure. The in-situ inhibition efficiency of GSCM to P ranged from 76.65% to 86.72%, exceeding that of commercial zeolite. The in-situ inhibition mechanism was controlled by sodium zeolite and riversideite, and concluded by the following:1) Substitution between [SiO4] tetrahedra (within the sodium zeolite structure), -OH (on the surface of materials) and [PO4], 2) Coordination of [PO4] tetrahedra with Al active site within the sodium zeolite structure, 3) Precipitation reaction between phosphate and slow-release of Ca2+ from the riversideite.

Study of Na+/K+-ATPase and Components of the Ca2+-transporting System in Myocardium under Experimental Prediabetes and Type 1 Diabetes in Rats

One of the complications of diabetes mellitus (DM) is diabetic cardiomyopathy (DCM), the molecular mechanisms of pathogenesis of which have not been fully studied. Previously, the involvement of Na+/K+-ATPase and components of the Ca2+ transport system in cardiomyocytes in the development of DCM was shown. The aim of the work was to study the expression and activity of Na+/K+-ATPase and Ca2+-ATPase (SERCA2) in the myocardium of male Wistar rats in a model of streptozotocin (STZ)-induced prediabetes and overt type 1 diabetes (T1DM). STZ was administered at once i. p. in dose of 30–35 mg/kg. Rats with glucose levels above 11 mM were considered diabetic (STZ-D1 group), and those with moderate hyperglycemia were considered prediabetic (STZ-preD1 group). The activity of Na+/K+-ATPase and Ca2+-ATPase was determined (by the rate of release of inorganic phosphate, Pi), and the expression of the genes α1- and α2-isoforms of Na+/K+-ATPase, SERCA2 and Kir6.1, Kv7.1 and Kv2.1 potassium channels. In the control (C) group, the activity of Mg2+-dependent ATPase (α1- and α2-isoforms of Na+/K+-ATPase), sensitive to 1 mM ouabain, was 6.03±0.6 mmol Pi/g/h. In the STZ-D1 and STZ-preD1 groups, Na+/K+-ATPase activity did not differ from group C. The level of gene expression of α1- and α2- subunits of Na+/K+-ATPase in the STZ-D1 group decreased by more than 45%, then both in the STZ-preD1 group increased by 64 and 81%, which may indicate a high sensitivity of expression to insulinopenia. The activity of Ca2+-ATPase and the expression of the SERCA2 gene did not differ between the groups – probably, the 4-week period after STZ administration is not sufficient for the development of Ca2+-ATPase deficiency in the rat heart. The level of expression of the genes of the potassium channel subtypes Kv2.1, Kir6.1 and Kv7.1 increased in the STZ-preD1 group, which may indicate a certain contribution of the studied potassium channel subtypes to the adaptation mechanism to moderate hyperglycemia.

Delivery system for dexamethasone phosphate based on a Zn2+-crosslinked polyelectrolyte complex of diethylaminoethyl chitosan and chondroitin sulfate

Hybrid nano- and microparticles based on metal ion crosslinked biopolymers are promising carriers for the development of drug delivery systems with improved biopharmaceutical properties. In this work, dexamethasone phosphate-containing particles based on chondroitin sulfate and chitosan or diethylaminoethyl chitosan additionally crosslinked with Zn2+ were prepared. Depending on the polycation/polyanion ratio in the system, anionic and cationic polyelectrolyte complexes (PECs) were obtained. The anionic Zn2+-containing and Zn2+-free PECs had sizes of 154 and 180 nm and ζ-potentials of −22.4 and −27.5 mV, respectively. The cationic Zn2+-containing and Zn2+-free PECs had sizes of 242 and 362 nm and ζ-potentials of 22.4 and 24.7 mV, respectively. The presence of Zn2+ in the system significantly prolonged the release of dexamethasone phosphate from the hybrid polyelectrolyte particle. The resulting release profiles of dexamethasone phosphate were in agreement with the Peppas-Sahlin kinetic model, which considers the combined effects of Fickian diffusion and polymer chain relaxation on the drug release rate. It was shown that the prolongation of drug release was mainly due to swelling and relaxation of the Zn2+ crosslinked polymers. The developed particles exhibited good mucoadhesive properties and pronounced anti-inflammatory activity, making them attractive candidates for biomedical applications.

Within Thermal Scales: The Kinetic and Energetic Pull of Chemical Entropy.

Biological systems are fundamentally containers of thermally fluctuating atoms that through unknown mechanisms are structurally layered across many thermal scales from atoms to amino acids to primary, secondary, and tertiary structures to functional proteins to functional macromolecular assemblies and up. Understanding how the irreversible kinetics (i.e., the arrow of time) of biological systems emerge from the equilibrium kinetics of constituent structures defined on smaller thermal scales is central to describing biological function. Muscle's irreversible power stroke - with its mechanochemistry defined on both the thermal scale of muscle and the thermal scale of myosin motors - provides a clear solution to this problem. Individual myosin motors function as reversible force-generating switches induced by actin binding and gated by the release of inorganic phosphate, P i . As shown in a companion article, when N individual switches thermally scale up to an ensemble of N switches in muscle, the entropy of a binary system of switches is created. We have shown in muscle that a change in state of this binary system of switches entropically drives actin-myosin binding (the switch) and muscle's irreversible power stroke, and that this simple two-state model accurately accounts for most key aspects of muscle contraction. Extending this observation beyond muscle, here I show that the chemical kinetics of an ensemble of N molecules differs fundamentally from a conventional chemical analysis of N individual molecules, describing irreversible chemical reactions as being pulled into the future by the a priori defined entropy of a binary system rather than being pushed forward by the physical occupancy of chemical states (e.g., mass action).

Synthesis of high-efficient low-cost fertilizer carriers based on biodegradable lignin hydrogels

Conventional fertilizers face environmental and economic challenges due to their high solubility, leading to significant losses via runoff and leachate. This study presents a biodegradable hydrogel, synthesized from lignin and polyvinyl alcohol (PVA), designed as an eco-friendly carrier for struvite (fertilizer) with controlled phosphate release. The hydrogel was analysed through scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA) and Differential scanning calorimetry (DSC). Furthermore, the prepared hydrogels demonstrated high water absorption capacities (963.4 %, 706.4 %, and 410 % for LH4, LH8, and LH12, respectively) and exhibited Fickian diffusion behaviour. Phosphate release studies showed a gradual release over 6–8 h with concentrations of 20.5 ppm, 19.45 ppm, and 17.85 ppm for St-LH4, St-LH8, and St-LH12. These lignin-based hydrogels offer a promising, cost-effective solution for slow-release fertilizers with high efficiency.

Remineralizing Effect and Ion Release of Pearl Powder versus Casein Phosphopeptide Amorphous Calcium Phosphate on Non-cavitated Initial Enamel Lesions: An In Vitro Study

Remineralizing Effect and Ion Release of Pearl Powder versus Casein Phosphopeptide Amorphous Calcium Phosphate on Non-cavitated Initial Enamel Lesions: An In Vitro Study

Myosin Isoform-Dependent Effect of Omecamtiv Mecarbil on the Regulation of Force Generation in Human Cardiac Muscle.

Omecamtiv mecarbil (OM) is a small molecule that has been shown to improve the function of the slow human ventricular myosin (MyHC) motor through a complex perturbation of the thin/thick filament regulatory state of the sarcomere mediated by binding to myosin allosteric sites coupled to inorganic phosphate (Pi) release. Here, myofibrils from samples of human left ventricle (β-slow MyHC-7) and left atrium (α-fast MyHC-6) from healthy donors were used to study the differential effects of μmolar [OM] on isometric force in relaxing conditions (pCa 9.0) and at maximal (pCa 4.5) or half-maximal (pCa 5.75) calcium activation, both under control conditions (15 °C; equimolar DMSO; contaminant inorganic phosphate [Pi] ~170 μM) and in the presence of 5 mM [Pi]. The activation state and OM concentration within the contractile lattice were rapidly altered by fast solution switching, demonstrating that the effect of OM was rapid and fully reversible with dose-dependent and myosin isoform-dependent features. In MyHC-7 ventricular myofibrils, OM increased submaximal and maximal Ca2+-activated isometric force with a complex dose-dependent effect peaking (40% increase) at 0.5 μM, whereas in MyHC-6 atrial myofibrils, it had no effect or-at concentrations above 5 µM-decreased the maximum Ca2+-activated force. In both ventricular and atrial myofibrils, OM strongly depressed the kinetics of force development and relaxation up to 90% at 10 μM [OM] and reduced the inhibition of force by inorganic phosphate. Interestingly, in the ventricle, but not in the atrium, OM induced a large dose-dependent Ca2+-independent force development and an increase in basal ATPase that were abolished by the presence of millimolar inorganic phosphate, consistent with the hypothesis that the widely reported Ca2+-sensitising effect of OM may be coupled to a change in the state of the thick filaments that resembles the on-off regulation of thin filaments by Ca2+. The complexity of this scenario may help to understand the disappointing results of clinical trials testing OM as inotropic support in systolic heart failure compared with currently available inotropic drugs that alter the calcium signalling cascade.

Analyzing the Bioactivity of a Novel Bone Cement: An In Vitro Study.

To analyze the effect of bioactivebone cement (BBC) placed in a phosphate buffer saline solution in comparison to mineral trioxide aggregate (MTA). Ten samples each of BBC (group 1) and MTA (group 2) were prepared and stored in a phosphate buffer saline solution. After three days of storage, white precipitates were formed on the surface of the samples. The solution with precipitates from each sample was analyzed for the presence of calcium and phosphate ions with coupled plasma atomic spectroscopy. BBC showed a significant amount of calcium and phosphate release after a seven-day storage period in phosphate buffer saline solution. Calcium release was significantly higher in group 1 (MTA) (p < 0.001) compared to that in group 2 (BBC), while group 2 (BBC) (p < 0.001) exhibited greater phosphate release compared to group 1 (MTA). BBC (group 2) retains its bioactivity when it comes into contact with a stimulated oral environment (STF). This demonstrates that BBC is bioactive in a simulated oral environment. Moreover, it retainedgood handling properties and could be easily manipulated into a dough form. Clinically, in cases of apical surgery, internal resorption or perforation repair where material placement poses difficulty, BBC will prove to be beneficial.

The analysis of release and percolation rate of nutrients from regular and obsidian-based slow-release fertilizers.

Research on the observation of nutrient release rates from slow-release and regular fertilizers combined with the percolation rate in the soil is scarce. This work aims to observe potassium and phosphate release behavior from slow-release and regular fertilizer, followed by the percolation of that nutrient in the soil. The characteristics of the soil were analyzed using X-ray Diffraction (XRD), X-ray Fluorescence (XRF), and Scanning Electron Microscope (SEM). The concentration of potassium and phosphate in soil is analyzed using Atomic Absorption Spectroscopy (AAS) and Ultraviolet-Visible Spectroscopy (UV-Vis), respectively. The release rate of nutrients from slow-release fertilizer is 6 to 8 times slower than regular fertilizer. Meanwhile, the rate of nutrients released from slow-release and regular fertilizer followed by soil percolation matches the quadratic equation. Potassium adsorption on the soil surface is significantly higher than that of potassium. The negativity of soil polarity contributed to the high level of potassium adsorption on soil particle surfaces. The low phosphate adsorption capability of magnetite and the negativity of soil polarity contributed to the soil's low phosphate adsorption.

Mechanism of A. oleivorans S4 treating soluble phosphorus deficiency and hydrocarbon contamination simultaneously

Both soluble phosphorus (P) deficiency and petroleum hydrocarbon contamination represent challenges in soil environments. While phosphate-solubilizing bacteria and hydrocarbon-degrading bacteria have been identified and employed in environmental bioremediation, the bacteria co-adapted to soluble P deficiency and hydrocarbon contamination has rarely been reported. This study explored the ability of Acinetobacter oleivorans S4 (A. oleivorans S4) to solubilize phosphate using n-hexadecane (H), glucose (G), and a mixed carbon source (HG) in tricalcium phosphate (TCP) medium. A. oleivorans S4 exhibited robust growth in H-TCP, releasing 31 mg L−1 of soluble P. Conversely, A. oleivorans S4 barely grew in G-TCP, releasing 654 mg L−1 of soluble P. In HG-TCP, biomass surpassed that in H-TCP, with phosphate release comparable to that in G-TCP. HPLC analysis revealed a small amount of TCA cycle acids in H-TCP and a large amount of gluconate in G-TCP and HG-TCP. Transcriptomic analysis showed elevated expression of genes associated with alkane degradation, P starvation, N utilization, and trehalose synthesis in H-TCP, revealing the molecular co-adaptation mechanism of A. oleivorans S4. Furthermore, the addition of glucose enhanced alkane degradation, P and N utilization, and reduced trehalose synthesis. It indicated that incomplete glucose metabolism may provide energy for other reactions, and the increase in soluble P mediated by gluconate may alleviate oxidative stress. Overall, A. oleivorans S4 proves promising for remediating soluble P-deficient and hydrocarbon-contaminated environments, and glucose stimulates its transformation into a super phosphate-solubilizing bacterium.

Aficamten is a small-molecule cardiac myosin inhibitor designed to treat hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an inherited disease of the sarcomere resulting in excessive cardiac contractility. The first-in-class cardiac myosin inhibitor, mavacamten, improves symptoms in obstructive HCM. Here we present aficamten, a selective small-molecule inhibitor of cardiac myosin that diminishes ATPase activity by strongly slowing phosphate release, stabilizing a weak actin-binding state. Binding to an allosteric site on the myosin catalytic domain distinct from mavacamten, aficamten prevents the conformational changes necessary to enter the strongly actin-bound force-generating state. In doing so, aficamten reduces the number of functional myosin heads driving sarcomere shortening. The crystal structure of aficamten bound to cardiac myosin in the pre-powerstroke state provides a basis for understanding its selectivity over smooth and fast skeletal muscle. Furthermore, in cardiac myocytes and in mice bearing the hypertrophic R403Q cardiac myosin mutation, aficamten reduces cardiac contractility. Our findings suggest aficamten holds promise as a therapy for HCM.

Phosphorus and bioenergy recovery from anaerobic co-digestion of food waste and corn residues with digested sludge: effect of HRT and pre-treatment methods

AbstractOrganic wastes from the human ecosystem including food waste (FW), agricultural waste and digested sludge (DS) from wastewater treatment can be utilized as valuable materials in anaerobic co-digestion (AcoD) for the dual purpose of bioenergy production and phosphorus (P) recovery through a chemical precipitation process. In this study, AcoD using FW and corn residues (CS) with DS for simultaneous sustainable phosphate release and biogas production were investigated. Different hydraulic retention times (HRT) of 10, 20, and 30 days were investigated, and FW was grinded, while CS pre-treatment methods including physical (FWCS), chemical (FWCS-Chem), and thermal (FWCS-Temp) were considered. The substrates of FW and CS compositions were conducted with a total organic loading of 6 g volatile solids (VS)/L/d (5 FW/1 CS) with a carbon-to-nitrogen ratio (C/N) of 24. The results indicate that FWCS-Chem showed the highest cumulative biogas production simultaneously with P release at HRT 20 days with 7279 L/m3 and 29.67%, respectively. Moreover, the effluent from all digesters exhibited a Mg/P ratio above 1, suitable for struvite precipitation without an external Mg source. Accordingly, FW, FWCS, and FWCS-Chem achieved P recovery rates of 63.64%, 69.75%, and 70.19% at 20-day HRT, with corresponding P contents in solids of 9.45, 9.43, and 8.29%, respectively. These values are comparable to commercial phosphate fertilizer containing 8.80% P. Moreover, incinerating the precipitating solids offers high-quality P concentrations in solids of up to 15.52, 16.32, and 16.31%, respectively. Hence, 20-day HRT was found to be the optimal condition for FW, CS, and DS for anaerobic co-digestion, resulting in the highest biogas production, P release, and maximum financial return for P recovery. Graphical abstract Phosphorus and bioenergy recovery from anaerobic co-digestion of food waste and corn residues with digested sludge.

Dilated cardiomyopathy mutation in beta-cardiac myosin enhances actin activation of the power stroke and phosphate release.

Inherited mutations in human beta-cardiac myosin (M2β) can lead to severe forms of heart failure. The E525K mutation in M2β is associated with dilated cardiomyopathy (DCM) and was found to stabilize the interacting heads motif (IHM) and autoinhibited super-relaxed (SRX) state in dimeric heavy meromyosin. However, in monomeric M2β subfragment 1 (S1) we found that E525K enhances (threefold) the maximum steady-state actin-activated ATPase activity (k cat) and decreases (eightfold) the actin concentration at which ATPase is one-half maximal (K ATPase). We also found a twofold to fourfold increase in the actin-activated power stroke and phosphate release rate constants at 30 μM actin, which overall enhanced the duty ratio threefold. Loaded motility assays revealed that the enhanced intrinsic motor activity translates to increased ensemble force in M2β S1. Glutamate 525, located near the actin binding region in the so-called activation loop, is highly conserved and predicted to form a salt bridge with another conserved residue (lysine 484) in the relay helix. Enhanced sampling molecular dynamics simulations predict that the charge reversal mutation disrupts the E525-K484 salt bridge, inducing conformations with a more flexible relay helix and a wide phosphate release tunnel. Our results highlight a highly conserved allosteric pathway associated with actin activation of the power stroke and phosphate release and suggest an important feature of the autoinhibited IHM is to prevent this region of myosin from interacting with actin. The ability of the E525K mutation to stabilize the IHM likely overrides the enhanced intrinsic motor properties, which may be key to triggering DCM pathogenesis.

Human cardiac β-myosin powerstroke energetics: Thin filament, Pi displacement, and mutation effects

The powerstroke of human cardiac β-myosin is an important stage of the cross-bridge cycle that generates force for muscle contraction. However, the starting structure of this process has never been resolved, and the relative timing of the powerstroke and inorganic phosphate (Pi) release is still controversial. In this study, we generated an atomistic model of myosin on the thin filament and utilized metadynamics simulations to predict the absent starting structure of the powerstroke. We demonstrated that the displacement of Pi from the active site during the powerstroke is likely necessary, reducing the energy barrier of the conformation change. The effects of the presence of the thin filament, the hypertrophic cardiomyopathy mutation R712L, and the binding of mavacamten on the powerstroke process were also investigated.

Biomimetic Charge‐Neutral Anion Receptors for Reversible Binding and Release of Highly Hydrated Phosphate in Water

AbstractControl of phosphate capture and release is vital in environmental, biological, and pharmaceutical contexts. However, the binding of trivalent phosphate (PO43−) in water is exceptionally difficult due to its high hydration energy. Based on the anion coordination chemistry of phosphate, in this study, four charge‐neutral tripodal hexaurea receptors (L1–L4), which were equipped with morpholine and polyethylene glycol terminal groups to enhance their solubility in water, were synthesized to enable the pH‐triggered phosphate binding and release in aqueous solutions. Encouragingly, the receptors were found to bind PO43− anion in a 1 : 1 ratio via hydrogen bonds in 100 % water solutions, with L1 exhibiting the highest binding constant (1.2×103 M−1). These represent the first neutral anion ligands to bind phosphate in 100 % water and demonstrate the potential for phosphate capture and release in water through pH‐triggered mechanisms, mimicking native phosphate binding proteins. Furthermore, L1 can also bind multiple bioavailable phosphate species, which may serve as model systems for probing and modulating phosphate homeostasis in biological and biomedical researches.

Biomimetic Charge-Neutral Anion Receptors for Reversible Binding and Release of Highly Hydrated Phosphate in Water.

Control of phosphate capture and release is vital in environmental, biological, and pharmaceutical contexts. However, the binding of trivalent phosphate (PO4 3-) in water is exceptionally difficult due to its high hydration energy. Based on the anion coordination chemistry of phosphate, in this study, four charge-neutral tripodal hexaurea receptors (L1-L4), which were equipped with morpholine and polyethylene glycol terminal groups to enhance their solubility in water, were synthesized to enable the pH-triggered phosphate binding and release in aqueous solutions. Encouragingly, the receptors were found to bind PO4 3- anion in a 1 : 1 ratio via hydrogen bonds in 100 % water solutions, with L1 exhibiting the highest binding constant (1.2×103 M-1). These represent the first neutral anion ligands to bind phosphate in 100 % water and demonstrate the potential for phosphate capture and release in water through pH-triggered mechanisms, mimicking native phosphate binding proteins. Furthermore, L1 can also bind multiple bioavailable phosphate species, which may serve as model systems for probing and modulating phosphate homeostasis in biological and biomedical researches.

Mechanism of phosphate release from actin filaments

After ATP-actin monomers assemble filaments, the ATP's [Formula: see text]-phosphate is hydrolyzedwithin seconds and dissociates over minutes. We used all-atom molecular dynamics simulations to sample the release of phosphate from filaments and study residues that gate release. Dissociation of phosphate from Mg2+ is rate limiting and associated with an energy barrier of 20 kcal/mol, consistent with experimental rates of phosphate release. Phosphate then diffuses within an internal cavity toward a gate formed by R177, as suggested in prior computational studies and cryo-EM structures. The gate is closed when R177 hydrogen bonds with N111 and is open when R177 forms a salt bridge with D179. Most of the time, interactions of R177 with other residues occlude the phosphate release pathway. Machine learning analysis reveals that the occluding interactions fluctuate rapidly, underscoring the secondary role of backdoor gate opening in Pi release, in contrast with the previous hypothesis that gate opening is the primary event.