Ion Bridges Research Articles

Contributions of mineral and organic cement agents to soil aggregation under potato production in Eastern Canada

Soil aggregation, a critical determinant of soil health and quality, results from the bonding of soil particles by various cementing agents, such as soil organic carbon, biota, ionic bridging, clay, and carbonates. This process varies across soil profiles due to agricultural practices and weathering disturbances. In this study, we analyzed the contribution of different cementing agents to soil aggregation within three soil horizons (Ap1, Ap2, and B) in potato production in Eastern Canada. We collected soil samples from 29 sites in Quebec Province for aggregate-size distribution analysis and cementing agent determination. Our findings reveal variations in aggregate proportions among the horizons, with horizon B exhibiting a smaller proportion of 2–4.75 mm aggregates (10.42%) compared to horizons Ap1 and Ap2 (20.28% and 18.71%, respectively). The hierarchy of cementing agents' impact on soil aggregation ranks polyvalent metals as the most influential, followed by organic matter (C&N) and silts and clays. However, accurately estimating aggregate stability through regression analysis based on these selected cementing agents remains challenging.

In‐Situ Self‐Respiratory Solid‐to‐Hydrogel Electrolyte Interface Evoked Well‐Distributed Deposition on Zinc Anode for Highly Reversible Zinc‐Ion Batteries

AbstractThe aqueous zinc‐ion batteries (AZIB) have emerged as a promising technology in the realm of electrochemical energy storage. Despite its potential advantages in terms of safety, cost‐effectiveness, and inherent safety, AZIB faces significant challenges. Issues attributed to unsupported thermodynamics and non‐uniform potential distribution and deposition, present formidable obstacles that necessitate resolution. To tackle these challenges, a novel strategy adapting hybrid organic–inorganic in situ derived solid‐to‐hydrogel electrolyte interface (StHEI) has been developed from coordination reactions and self‐respiratory process, establishing uniform diffusion channels by ion bridges and accelerating ion transport. Self‐respiratory pattern of StHEI realized through in situ inorganic component conversion further prolongs the protecting duration, which effectively mitigates corrosion and passivation but enhance the mechanical properties of the StHEI measured through Young's modulus. This novel StHEI promotes well‐distributed potential lines within the Helmholtz regions. Zn2+ are finally induced to deposit and nucleate in a compact, fine, and uniform manner. Asymmetrical batteries assembled with the modified Zn electrode and bare Zn exhibit exceptional stability over 3000 h (1 mA cm−2–0.5 mAh cm−2). The asymmetrical Cu//Zn cell achieved an outstanding average Coulombic efficiency (CE) of 99.6 % over 1200 cycles.

In-Situ Self-Respiratory Solid-to-Hydrogel Electrolyte Interface Evoked Well-Distributed Deposition on Zinc Anode for Highly Reversible Zinc-Ion Batteries.

The aqueous zinc-ion batteries (AZIB) have emerged as a promising technology in the realm of electrochemical energy storage. Despite its potential advantages in terms of safety, cost-effectiveness, and inherent safety, AZIB faces significant challenges. Issues attributed to unsupported thermodynamics and non-uniform potential distribution and deposition, present formidable obstacles that necessitate resolution. To tackle these challenges, a novel strategy adapting hybrid organic-inorganic in situ derived solid-to-hydrogel electrolyte interface (StHEI) has been developed from coordination reactions and self-respiratory process, establishing uniform diffusion channels by ion bridges and accelerating ion transport. Self-respiratory pattern of StHEI realized through in situ inorganic component conversion further prolongs the protecting duration, which effectively mitigates corrosion and passivation but enhance the mechanical properties of the StHEI measured through Young's modulus. This novel StHEI promotes well-distributed potential lines within the Helmholtz regions. Zn2+ are finally induced to deposit and nucleate in a compact, fine, and uniform manner. Asymmetrical batteries assembled with the modified Zn electrode and bare Zn exhibit exceptional stability over 3000 h (1 mA cm-2-0.5 mAh cm-2). The asymmetrical Cu//Zn cell achieved an outstanding average Coulombic efficiency (CE) of 99.6 % over 1200 cycles.

Modulation of irrigation-induced microbial nitrogen‑iron redox to per- and polyfluoroalkyl substances' water-soil interface release in paddy fields: Activation or immobilization?

Understanding the modulation of paddy field irrigation to the migration of per- and polyfluoroalkyl substances (PFAS) at the water-soil interface is pivotal for the management of PFAS pollution in paddy soil and surrounding surface water environments. In flooded soils, soil organic matter was transformed into aromatic protein-like dissolved organic matter (DOM). Meanwhile, Na+, K+, and Mg2+ were translocated into extracellular polymeric substances (EPS) under the catalysis of cation channel enzymes (p < 0.05), provided ion bridging for the binding of DOM and PFAS, and accelerated the accumulation of C4–C9 PFAS in overlying water (41.79–99.14 %). Short-chain PFAS's accumulation in soil solution of drought soils was stimulated by microorganisms secreting soluble microbial by-product-like DOM (53.15–97.96 %). Furthermore, PFAS's distribution in flood soils was dominated by bacterial denitrification and iron-reduction, whereas iron-oxidation and ammoxidation controlled that in drought soils. The transformation of organic carbon including CO and COC caused by irrigation-induced redox modulated PFAS cross-media translocation. Iron‑nitrogen redox in flooded paddy soils immobilized the PFAS's migration into overlying water (p < 0.05). Our findings have profound implications for PFAS's pollution control, surface water environmental protection, and rice production security in paddy fields.

Scalable ultrastrong MXene films with superior osteogenesis.

Titanium carbide MXene flakes have promising applications in aerospace, flexible electronic devices and biomedicine owing to their superior mechanical properties1 and electrical conductivity2 and good photothermal conversion3, biocompatibility4 and osteoinductivity5. It is highly desired yet very challenging to assemble MXene flakes into macroscopic high-performance materials in a scalable manner. Here we demonstrate a scalable strategy to fabricate high-performance MXene films by roll-to-roll-assisted blade coating (RBC) integrated with sequential bridging, providing good photothermal conversion and osteogenesis efficiency under near-infrared irradiation. MXene flakes were first bridged with silk sericin by hydrogen bonding and then assembled into macroscopic films using a continuous RBC process, followed by ionic bridging to freeze their aligned structure. The resultant large-scale MXene films with strong interlayer interactions are highly aligned and densified, exhibiting high tensile strength (755 MPa), toughness (17.4 MJ m-3) and electromagnetic interference (EMI) shielding capacity (78,000 dB cm2 g-1), as well as good ambient stability, photothermal conversion and bone regeneration performance. The proposed strategy not only paves a feasible way for realizing the practical applications of MXene in the fields of flexible EMI shielding materials and bone tissue engineering but also provides an avenue for the high-performance and scalable assembly of other two-dimensional flakes.

Immobilization of Coupled Enzymes onto Metalated Hierarchical Organic Microspheres.

Hierarchical organic microspheres (HOMs) have emerged as an ideal carrier for immobilizing biomacromolecules. In this research, an in-depth investigation into the structural characteristics of a striated HOM, known as HOM-15, has revealed the assembly mechanism of microspheres through weakly stacked two-dimensional structural units that are composed of V-shaped small organic molecules. With the leverage of this understanding, HOM-15 was adopted as a stable and reusable platform for co-immobilizing of ene-reductases and glucose dehydrogenases via metal ion bridging onto the surface of HOMs. The research demonstrates that metal ion bridging can finely tune the surface properties of HOM-15, thereby facilitating the immobilization of enzymes that would otherwise be impeded by electrostatic repulsion. Comparing HOM-15 to other microspherical variants revealed its superior biocatalytic performance, attributed to the reduction of the mass transfer barrier facilitated by its lamellar-stacking morphology. This novel biocatalytic system underscores the potential applications of HOMs in broader biocatalytic processes.

Effect of anionic polyacrylamide amendment on the climatic durability of solidified waste rock fine

In order to improve the climatic durability of solidified waste rock fine (WRF), anionic polyacrylamide (APAM) was innovatively introduced to amend solidified WRF in this study. The effects of APAM content, freeze-thaw (F-T), and wet-dry (W-D) cycles on the mechanical behaviors of solidified WRF were explored. After that, zeta potential, fourier transform infrared (FTIR) spectroscopy, and scanning electron microscope (SEM) tests were initiated to understand the behavioral mechanisms of APAM. The results show that APAM can significantly improve the mechanical properties and durability of solidified WRF, and there exist a threshold content of APAM (0.3 %∼0.8 % in this study), beyond which the strength will decrease. The microscopic test shows that the bridging effect and the filming effect induced by APAM are considered to be the two decisive factors affecting the mechanical behavior of S-WRF. On the one hand, the linear APAM long chain enables the cohesion between particles to be stronger through ion bridging, on the other hand, the long chains cross-link with each other to form a network interwoven inside the structure, thus playing a microfabric reinforcement role and enhancing the crack resistance of the solidified matrix. In addition, life cycle assessment (LCA) further confirmed the advantages of using industrial by-products combined with APAM to amend solidified-WRF. These results provide a theoretical basis for using APAM as trace additives to mitigate climatic durability-related issues.

Asphaltene-Silica Interactions in Salinity Water and Their Ion Dependence

Summary The adsorption of asphaltene on the pore surface not only forms a dense adsorption film but also induces a transition in sandstone wettability to more hydrophobic, which poses challenges to oil displacement, especially in unconventional reservoirs. The asphaltene adsorption exhibits a strong ion dependence, especially toward high ion concentration and high-valence cations, and the mechanism is not yet entirely understood. In this work, atomic force microscopy (AFM), coreflooding experiments, and the self-priming rate method were used to investigate the impacts of ion concentration and types in connate water on the adsorption of asphaltene. Enhanced asphaltene adsorption is observed in the presence of ions, leading to a more pronounced hydrophobic character in the cores saturated by high-salinity water. Then, we proceed with a consideration of the attraction force law between asphaltene and rock. The attraction showed an exponential decay with respect to distance and is in accordance with the hydrated ion bridge interaction. Furthermore, the attraction intensified notably in CaCl2 solution compared to that in NaCl solution and was enhanced progressively with increasing ionic concentration. Therefore, the adsorption amount of asphaltene and ultimately the wettability of the rock are affected by ion concentration and valence in formation water. Our findings hold significant implications for enhancing oil recovery in unconventional reservoirs under high-salinity conditions.

High-density, reversible of hydrogen-bonding and Fe3+ ion bridging enable the fabrication of multifunctional PVA-based composites

The development of continuously degradable and recyclable polymeric composites with superb mechanical properties, which can extend the service life of materials and reduce the environmental impact, will make a significant contribution to global sustainability. In this study, poly(vinyl alcohol) (PVA)-based composites (D-PVA-Fe-TA) with degradability, recyclability and excellent mechanical properties are prepared by complexation of 3,4-dihydroxybenzaldehyde-grafted PVA (D-PVA), tannin (TA) and Fe3+ ions in dimethyl sulfoxide (DMSO), and then dialysis in deionized water and glycerol (Gly). The two-step dialysis process, playing a crucial role in reducing the free water of D-PVA-Fe-TA composites, enhances the formation of reversible of hydrogen-bonding and the reinforcement of self-assembled Fe3+-chelation between TA and D-PVA, and facilitates the fabrication of PVA-based composites with a breaking strength of ≈ 18.7 MPa, an elongation at break of ∼ 812 % and a toughness of ≈ 86.81 MJ/m3; Meanwhile, the resulting homogeneous and dense structure of D-PVA-Fe-TA composites hinders the penetration of Gly solution, thereby enhancing the bonding strength and environmental adaptability of D-PVA-TA-Fe composites within the temperature range of −20℃ to 60℃. Furthermore, the as-prepared D-PVA-TA-Fe composites exhibit recyclability for multiple cycles. When placed under soil culture medium, the resulting composites can be degraded without the need for manual interference. This study presents a novel strategy for the fabrication of materials possessing excellent mechanical strength, environmental adaptability, recyclability and degradation, which have great potential for taking the place of conversional composites in specific conditions.

Experimental and molecular simulation study on the influence of chain length and anion structure of ionic liquids on the wettability of highly hydrophobic bituminous coal

The wettability of bituminous coal is critical for the coal dust suppression and can be apparently modulated by ionic liquids. However, the modulation mechanism still remains elusive. Here, a combination of macroscopic experiments, mesoscopic characterization, and microscopic simulations (quantum mechanics and molecular dynamics) are leveraged to parse the effect on the wettability of coal dust surfaces of three novel ionic liquids ([C12MIm]Br, [BMIm]Br, [BMIm]Cl) featuring the varying chain lengths and anions in the coal-water system. The results show that the selected ionic liquids exert a distinct bridging function from traditional surfactants which invoke the hydrogen bonding interaction. This ionic liquids-mediated bridging mechanism heavily depends on their chain length structure, which can firstly penetrate deeply the internal pores of coal dusts and then adsorb on the coal surfaces to rapidly strike a dynamic equilibrium. Ionic liquids interacting with coal dust can primarily reduce the energy difference between polar and nonpolar interactions within coal dust, thereby enhancing the electrostatic interactions between coal dust and water molecules and effectively improving coal dust wetting properties. These findings provide a theoretical basis for the rational design of high-performance ionic liquids for coal mine dust control.

Improving strength and toughness of graphene film through metal ion bridging

The fangs, jaws, and mandibles of marine invertebrates such as Chiton and Glycera show excellent mechanical properties, which are mostly contributed to the interactions between metal (Fe, Cu, Zn, etc.) and oxygen-containing functional groups in proteins. Inspired by these load-bearing skeletal biomaterials, we improved tensile strength and toughness of graphene films through bridging graphene oxide (GO) nanosheets by metal ions. By optimizing the metal coordination form and density of cross-linking network. We revealed the relationship between mechanical properties and the unique spatial geometry of the GO nanosheets bridged by different valence metal ions. The results demonstrated that the divalent metal ions form tetrahedral geometry with carboxylate groups on the edges of the GO nanosheets, and the bond energy is relatively low, which is helpful for improving the toughness of resultant graphene films. While the trivalent metal ions are easily to form octahedral geometry with the GO nanosheets with higher bond energy, which is better for enhancing the tensile strength of graphene films. After reduction, the reduced GO (rGO) film bridged by divalent metal ions shows 43% improvement in toughness, while the rGO film bridged by trivalent metal ions shows 64% improvement in tensile strength. Our work reveals the mechanism of metal coordination bond energy and spatial geometry to improve the mechanical properties of graphene films, which lays a theoretical foundation for improving the tensile strength and toughness of resultant graphene films, and provides an avenue for fabricating high-performance graphene films and other two-dimensional nanocomposites.

Dexamethasone sodium phosphate loaded nanoparticles for prevention of nitrogen mustard induced corneal injury

Nitrogen mustard (NM) is a potent vesicating chemical warfare agent that is primarily absorbed through skin, inhalation, or ocular surface. Ocular exposure of NM can cause acute to chronic keratopathy which can eventually lead to blindness. There is a current lack of effective countermeasures against ocular exposure of NM despite their imperative need. Herein, we aim to explore the sustained effect of Dexamethasone sodium phosphate (DSP)-loaded polymeric nanoparticles (PLGA-DSP-NP) following a single subconjunctival injection in the management and prevention of corneal injury progression upon exposure to NM. DSP is an FDA approved corticosteroid with proven anti-inflammatory properties. We formulated PLGA-DSP-NP with zinc chelation ion bridging method using PLGA polymer, with particles of approximately 250 nm and a drug loading of 6.5 wt%. Under in vitro sink conditions, PLGA-DSP-NP exhibited a sustained drug release for two weeks. Notably, in NM injured cornea, a single subconjunctival (SCT) injection of PLGA-DSP-NP outperformed DSP eyedrops (0.1%), DSP solution, placebo NP, and saline, significantly mitigating corneal neovascularization, ulceration, and opacity for the two weeks study period. Through PLGA-DSP-NP injection, sustained DSP release hindered inflammatory cytokine recruitment, angiogenic factors, and endothelial cell proliferation in the cornea. This strategy presents a promising localized corticosteroid delivery system to effectively combat NM-induced corneal injury, offering insights into managing vesicant exposure.

Facile fabrication of high-strength biocomposite through Mg2+-enhanced bonding in bamboo fiber

The emerging interests in high-performance biocomposites grows significantly driven by their superior environmental sustainability. This study proposes a unique biocomposite strategy by implementing an acetic and ball-milled treatment to disrupt the bamboo cell wall structure, thereby facilitating further processing by effectively increasing the active sites and specific surface area in the bamboo fiber. The fibers are subsequently carboxymethylated to introduce carboxyl groups which facilitate physical bonding between the fibers and Mg2+ ions that are added to the system. These ions form metal-coordination bonds with the carboxyl groups, acting as ion bridges that significantly strengthen the inter-fiber bonding. The resulted biocomposite exhibits impressive mechanical properties, including a high tensile strength (94.24 MPa) and flexural strength (104.14 MPa), not only that, changes in elastic modulus also highlight changes in fiber bonding, the flexural modulus is 21.29 GPa and the tensile modulus is 7.01 GPa. Moreover, it maintains a low water uptake capacity of only 6.8 % despite being submerged for 12 h. The thermal conductivity and fire retardancy have also been improved. The synergic bonding ability between the cellulose and lignin in the fibers, coupled with the glue-free thermoforming process, enhances the material performance and renders it fully recyclable, thus reducing environmental pollution and providing cost-effective engineering materials to society.

Target-Mediated Fluoroquinolone Resistance in Neisseria gonorrhoeae: Actions of Ciprofloxacin against Gyrase and Topoisomerase IV.

Fluoroquinolones make up a critically important class of antibacterials administered worldwide to treat human infections. However, their clinical utility has been curtailed by target-mediated resistance, which is caused by mutations in the fluoroquinolone targets, gyrase and topoisomerase IV. An important pathogen that has been affected by this resistance is Neisseria gonorrhoeae, the causative agent of gonorrhea. Over 82 million new cases of this sexually transmitted infection were reported globally in 2020. Despite the impact of fluoroquinolone resistance on gonorrhea treatment, little is known about the interactions of this drug class with its targets in this bacterium. Therefore, we investigated the effects of the fluoroquinolone ciprofloxacin on the catalytic and DNA cleavage activities of wild-type gyrase and topoisomerase IV and the corresponding enzymes that harbor mutations associated with cellular and clinical resistance to fluoroquinolones. Results indicate that ciprofloxacin interacts with both gyrase (its primary target) and topoisomerase IV (its secondary target) through a water-metal ion bridge that has been described in other species. Moreover, mutations in amino acid residues that anchor this bridge diminish the susceptibility of the enzymes for the drug, leading to fluoroquinolone resistance. Results further suggest that ciprofloxacin primarily induces its cytotoxic effects by enhancing gyrase-mediated DNA cleavage as opposed to inhibiting the DNA supercoiling activity of the enzyme. In conclusion, this work links the effects of ciprofloxacin on wild-type and resistant gyrase to results reported for cellular and clinical studies and provides a mechanistic explanation for the targeting and resistance of fluoroquinolones in N. gonorrhoeae.

Mechanical characterization and water stability of loess improved by bio-based materials: An eco-friendly approach

Loess exhibits poor engineering properties, such as low strength and poor water stability. Conventional materials used for improving loess, such as cement and lime, result in environmental pollution issues throughout their production and application processes. To assess the efficacy of bio-based materials, including calcium alginate (CA), xanthan gum (XA), cotton fibers (CO) and flax fibers (FA) in the treatment of loess, the improved soil's strength, disintegration, and water resistance were examined. Subsequently, an optimal amendment approach was determined, and dry-wet cycle tests and microscopic observation were performed. The results show that 1.0 % calcium alginate can effectively enhance the strength of loess, significantly improving its resistance to disintegration with almost no observable disintegration; permeability is significantly reduced, and water repellency is enhanced. 2.0 % xanthan can improve the strength and disintegration resistance of loess, but the improvement in strength is lower than that of calcium alginate. Additionally, the improved soil with XA experiences a flocculent disintegration in static water, which cannot maintain the soil structure. Cotton fibers and flax fibers can enhance both compressive and tensile strength of the soil. The content of 0.45 % flax fibers is considered the optimal choice as it has no effect on water stability. Combining the above results, the combination of 1.0 % CA and 0.45 % FA has been selected to improve the loess, which effectively improves the comprehensive mechanical properties and water stability of the composite improved soil. The decrease in strength and mass loss rate are significantly reduced after dry-wet cycle tests. Microscopic tests show that calcium alginate connects soil particles by Ca2+ ionic bridges, which allows the cementing materials to fill the loess pores and exert the role of agglomeration and coagulation to enhance the integrity of the loess. This study shows that the bio-based material with calcium alginate as the main body can effectively improve the mechanical strength and water stability of the loess.

Redox-dependent Cd2+ inhibition of BK-type Ca2+-activated K+ channels

Large-conductance Ca2+-activated K+ channels (BK channels) are formed by Slo1 subunits as a homotetramer. Besides Ca2+, other divalent cations, such as Cd2+, also activate BK channels when applied intracellularly by shifting the conductance-voltage relation to more negative voltages. However, we found that if the inside-out patch containing BK channels was treated with solution containing reducing agents such as dithiothreitol (DTT), then subsequent Cd2+ application completely inhibited BK currents. The DTT-dependent Cd2+ inhibition could be reversed by treating the patch with solutions containing H2O2, suggesting that a redox reaction regulates the Cd2+ inhibition of BK channels. Similar DTT-dependent Cd2+ inhibition was also observed in a mutant BK channel, Core-MT, in which the cytosolic domain of the channel is deleted, and in the proton-activated Slo3 channels but not observed in the voltage-gated Shaker K+ channels. A possible mechanism for the DTT-dependent Cd2+ inhibition is that DTT treatment breaks one or more disulfide bonds between cysteine pairs in the BK channel protein and the freed thiol groups coordinate with Cd2+ to form an ion bridge that blocks the channel or locks the channel at the closed state. However, surprisingly, none of the mutations of all cysteine residues in Slo1 affect the DTT-dependent Cd2+ inhibition. These results are puzzling, with an apparent contradiction: on one hand, a redox reaction seems to regulate Cd2+ inhibition of the channel, but on the other hand, no cysteine residue in the Slo1 subunit seems to be involved in such inhibition.

Specific ions effect on aggregation behaviors and structural changes of amyloid fibrils from rice glutelin

Metal ions have been considered as an important factor on fibrils assembly. Herein, a comprehensive analysis of specific ions effect on fibril formation and structural changes was investigated. The addition of ions (except Zn2+) accelerated the aggregation kinetics of rice glutelin fibrils (RGFs) from 0.93 to 1.28–2.19 h−1. In addition, the fibrillization rate followed the order of NH4+ > Li+ > Na+ > K+ > Cu2+ > Mg2+ > Ca2+ > Zn2+. The highest yield and length of fibrils were observed with Ca2+, probably due to the ionic bridging effect and hydrated capacity of Ca2+. However, Cu2+ reduced the fibrils yield, which was attributable to the fact that Cu2+ disrupted β-sheet structure and inhibited the transition of monomer to fibrils. The polymorphism of fibrils was observed with different salts, and the light metals presented a superior effect on fibrils formation than heavy metals. Overall, this work will provide a further information into how to tune the structure of RGFs using various ions.

Assembly of anionic silver nanoclusters with controlled packing structures through site-specific ionic bridges.

The assembly of metal nanoclusters (NCs) into crystalline lattice structures is of interest in the development of NC-based functional materials. Here we demonstrate that the assembled structures of tri-anionic tetrahedral symmetric [Ag29(BDT)12]3- (Ag29 NC, BDT: 1,3-benzenedithiol) NCs are controlled into a polyethylene-like zigzag chain and a "poly-ring-fused-cyclohexane"-like honeycomb arrangement through ionic interactions with alkali metal cations such as K+ and Cs+. The site-specific binding of alkali metal ions on the tetrahedrally arranged binding sites of Ag29 NCs successfully connects the adjacent NCs into various packing modes. The number and type of bridges between NCs determine the Ag29 NC packing structures, which are affected by the solvent species, enabling the transformation of packing modes in the single-crystalline state. The photoluminescence (PL) properties of the crystals responded to the packing modes of the NCs in terms of anisotropy and bridge linkage style inducing a varied degree of relaxation of the excited state depending on the relocation mobility of alkali metal ions in the crystals.

A unified viscoelastic constitutive model for studying the mechanical behaviors of polyelectrolyte complex hydrogels with different crosslinker degrees

Bio-based hydrogels formed by the chemically or physically cross-links are promising materials in the biological system. In this paper, we propose a constitutive model within the framework of finite-strain viscoelasticity to investigate the mechanical behaviors of bio-based polyelectrolyte complex (PEC) hydrogels from the ionic complexation of sodium hyaluronate (HA)/chitosan with and without chemical crosslinkers. The structure of the viscoelastic constitutive model consists of a spring and a Kelvin element, in which two softening factors are adopted to represent the states of ionic bonds and bridges in the hydrogels. Based on some constitutive assumptions and through the conventional approach of thermodynamics, the constitutive equation system of the model is derived. Corresponding to the hydrogels with different crosslinker concentrations, the values of material parameters in the model are identified. To show the validity of the model, it is applied to simulate the mechanical behaviors of the hydrogel samples in the uniaxial tensile tests and cyclic loading–unloading tests. It is found that the model predictions can fit the experimental data quite well. Based on the modeling results, some further analyses regarding the effects of softening factors on the response of HA/chitosan hydrogels have also been conducted.

Scots pine defensins inhibit Ips acuminatus α-amylase activity

Background. Pine bark beetle Ips acuminatus (Gyllenhal, 1827) is one of the most harmful pests of pine trees as it affects the phloem of the upper part of the stem and branches, disrupting the flow of nutrients and water to the crown. I. acuminatus feeds by plant tissues rich in starch, so α-amylases must play a pivotal role in the carbohydrate metabolism of these insects. However, in conifer bark beetles, α-amylases remain poorly understood. Materials and Methods. To detect the α-amylase activity in the digestive system of I. acuminatus, we obtained extracts from larvae, pupae, and adults that were collected from naturally infested Scots pine. The α-amylase activity of crude extracts from different stages and parts of the bark beetle’s body was assessed using 1% starch agar plates. The quantitative evaluation of the α-amylase inhibitory activity of recombinant defensins PsDef1, PsDef2, and PsDef5.1 was performed using the Bernfeld method. The docking models of Scots pine defensins and Ips typographus L. α-amylase (AmyIp) complexes were predicted using the ClusPro 2.0 web server. Results and Discussion. As a result, we found the presence of α-amylase activity in the digestive systems of both larvae and adults of I. acuminatus, but not in pupae. All tested defensins, PsDef1, PsDef2, and PsDef5.1, exhibited inhibitory activity against insect α-amylase at micromolar concentrations. The IC50 values for these peptides were 4.9±0.6 μM, 4.6±0.8 μM, and 2.8±0.5 μM, respectively. In the PsDefs-AmyIt complexes, a network of hydrogen bonds, ionic bridges, and nonbonded contacts are formed between the enzyme and its inhibitor, which prevents the substrate from reaching the catalytic site. The PsDef5.1-AmyIt complex has the largest interfacial contact area, 2328 Å2, in comparison with two other defensins, which correlates well with the inhibitory activity of defensins in this study. Conclusion. Thus, we have identified α-amylase activity in I. acuminatus and demonstrated the ability of Scots pine defensins to inhibit it, sugges­ting that they play a role in pine defenses against this pest.