Weak Hydrogen Bonds Research Articles

Influence of Number and Strength of Hydrogen Bonds on Fracture Property and Microscopic Mechanisms of Associative Hydrogen-Bonded Polymers via Molecular Dynamics Simulation.

A coarse-grained model combining the acceptor-hydrogen-donor 3-body potential is first developed in this work to explore the fracture property and microscopic mechanisms of associative hydrogen-bonded polymers (AHBPs). Next, a triaxial deformation mode is performed to reveal that the fracture toughness of AHBPs initially improves and then is reduced as the number of active groups increases. By characterizing the stress decomposition, the strong hydrogen bond (HB) network improves the maximum stress but reduces the elongation. The destructive process of the HB network is described by quantifying the broken number and reduced energy of HBs. Interestingly, the strength of a single HB first decreases and then rises with strain. The initial decrease is mainly caused by the disruption of strong/moderate HBs, while the following rise is due to the further breakage of weak HBs and partial recovery of strong/moderate HBs. Meanwhile, the formed clusters of HBs due to the self-attraction act as the physical cross-links, whose evolution process is recorded by analyzing their number and size. Following it, the orientation degree and asphericity factor are calculated with strain to reflect the change in chain configuration, which is influenced by the HB network. Subsequently, the nucleation and growth process of voids is quantified. More than 90% of voids are nucleated in the polymer region, while others are in the HB region, which can be proved by the local elastic modulus and snapshots. The growth and coalescence rate of the voids can be suppressed by the strong HB network. Finally, the fracture toughness of AHBPs exhibits a continuous increase with improving strength of HBs due to the strong HB network. In summary, our work presents a clear and novel comprehension of the fracture property of AHBPs at the molecular scale.

The bonded interfacial layer structure of α-Al2O3 (0001)/water at different pH values studied by sum frequency vibrational spectroscopy.

Oxide/water interfaces are ubiquitous, with alumina/water drawing particular interest due to its environmental and industrial applications. Understanding the interfacial structure at the molecular level is crucial for many physical and chemical processes occurring there. However, the exact structure of interfacial H-bonded network at different pH values remains unclear. Here, sum-frequency vibrational spectroscopy in the OH stretch region was employed to study α-Al2O3 (0001)/water interface at different pH values, while suppressing the contribution of the diffusion layer by adding salts. The experimental results revealed although the variation of pH can charge the surface, it has little impact on the structure of the bonded interfacial layer (BIL). The interaction between alumina and water is mainly governed by weak hydrogen bonds. Furthermore, the templating effect of α-Al2O3 (0001) on the interfacial H-bonded network was observed, with the O-H stretch mode of ∼3430cm-1 exhibiting anisotropy consistent with the (0001) surface symmetry. These findings indicate that the BIL structure on Al2O3 (0001) is predominantly influenced by the surface atom configuration, and the effect of charge changes induced by pH on the BIL structure is negligible.

Effect of a single water molecule on the conformational preferences of a capped Pro–Gly dipeptide in the gas phase

Herein, we have investigated the effect of microhydration on the secondary structure of a capped dipeptide Boc-DPro-Gly-NHBn-OMe (Boc = tert-butyloxycarbonyl, Bn = Benzyl), i.e., Pro–Gly (PG) with a single H2O molecule using gas-phase laser spectroscopy combined with quantum chemistry calculations. Observation of a single conformer of the monohydrated peptide has been confirmed from IR-UV hole-burning spectroscopy. Both gas-phase experimental and theoretical IR spectroscopy results confirm that the H2O molecule is inserted selectively into the relatively weak C7 hydrogen bond (γ-turn) between the Pro C=O and NHBn N–H groups of the peptide, while the other C7 hydrogen bond (γ-turn) between the Gly N–H and Boc C=O groups remains unaffected. Hence, the single H2O molecule in the PG⋯(H2O)1 complex significantly distorts the peptide backbone without appreciable modification of the overall secondary structural motif (γ–γ) of the isolated PG monomer. The nature and strength of the intra- and inter-molecular hydrogen bonds present in the assigned conformer of the PG⋯(H2O)1 complex has also been examined by natural bond orbital and non-covalent interaction analyses. The present investigation on the monohydrated peptide demonstrates that several H2O molecules may be required for switching the secondary structure of PG from the double γ-turn to a β-turn that is favorable in the condensed phase.

“Three birds with one stone” strategy for building easily reprocessable cellulosic thermosetting resins

Cellulose is the most abundant natural polypolysaccharide and is an ideal raw material to replace petroleum-based plastics. However, natural cellulose is difficult to be thermo-processed like conventional plastics because of the rich and strong hydrogen bonds interactions. In this study, a series of dialdehyde derivatives of cellulose (DACs) were prepared by periodate oxidation of cellulose, and cellulose covalent adaptive networks based on acetal dynamic covalent bonds (ACCs) were prepared using dipentaerythritol as a crosslinker for DAC. This strategy can introduce acetal bonds, weaken hydrogen bonds, and reduce rigidity to kill three birds with one stone. The excellent reprocessing performance of ACCs is attributed to the reconstruction of the cellulose hydrogen bond network by acetal bonds, and the reversible exchange reaction of the acetal bonds at high temperatures endows the cellulose chains with mobility, allowing ACCs to be remodeled by hot pressing at 90°C for 15 min. The excellent stability and reprocessability of ACCs hold the promise of replacing current non-renewable petroleum-based plastics and provide inspiration for the development of other types of biomass plastics.

The formation of protein coronas and the interaction of soy protein isolate and whey protein isolate with starch nanoparticles

The influence of food components on the physicochemical properties and biological responses of nanoparticles is pivotal. Since soy protein isolate (SPI) and whey protein isolate (WPI) are commonly used as plant and animal proteins in food, it is imperative to gain comprehensive knowledge of the interaction between SPI/WPI and nanoparticles. Accordingly, we examined the adsorption of SPI and WPI onto starch nanoparticles (SNPs) and their associated interactions. SNP aggregation was observed in the SPI/WPI, and coronas formed around the surfaces of the SNPs. The binding of the protein isolates reduced the zeta potential of the SNPs from −10.34 to −26.5 mV for the SPI and to −21.37 mV for the WPI. However, mixing the SNPs with the protein isolates did not alter the microenvironment of aromatic amino acids and had no substantial impact on the secondary structure of the proteins. Thermogravimetric analysis revealed that the formation of SPI/WPI coronas enhanced the thermal stability of the SNPs. Isothermal titration calorimetry indicated that the adsorption of the SPI and WPI onto the SNPs was driven primarily by weak van der Waals forces and hydrogen bonds. This study facilitates the predicting of organic nanoparticle behaviours in complex food matrix and human gastrointestinal environments.

Characterization of acetolactate synthase genes and resistance mechanisms of multiple herbicide resistant Lolium multiflorum

Combining imidazolinone-tolerant wheat with imazamox presents an effective solution to combat weed resistance. However, Lolium multiflorum, a troublesome resistant weed infesting wheat fields, may have developed resistance to imazamox, and the potential resistance mechanisms are intriguing. In this study, we explored the susceptibility of L. multiflorum to imazamox and investigated the resistance mechanisms, including the contribution of the target enzyme acetolactate synthase (ALS) to resistance and the presence of non-target-site resistance (NTSR). Eight L. multiflorum populations suspected of being resistant to imazamox were collected, and six populations exhibited resistance, ranging from 2.45-fold to 16.32-fold. The LmALS1 gene from susceptible population D3 plants and multiple copies of the LmALS gene (LmALS1, LmALS2, LmALS2α, LmALS3, LmALS3α, LmALS3β) from resistant populations D5 and D8 plants were separately amplified. Two mutations (Pro/Gln197 to Thr, Trp574 to Leu) were found in LmALS1 in the resistant populations. Compared to D3, LmALS1 was overexpressed in D5 but not in D8. The presence of LmALS1 mutants (LmALS1-Thr197 and LmALS1- Leu574), along with LmALS2, LmALS3, and their subunits, contribute to the resistance phenotype by increasing bonding energies, weakening hydrogen bonds, or decreasing protein binding pocket volumes and surface area. Additionally, D5 and D8 populations exhibited multiple resistance (>40-fold) to three other ALS inhibitors: pyroxsulam, flucarbazone-sodium, and mesosulfuron-methyl. Pre-treatment with malathion and 4-chloro-7-nitrobenzoxadiazole (cytochrome P450 monooxygenase and glutathione S-transferase inhibitors respectively) reversed the resistance of the D8 population and partially reversed the resistance of the D5 population to imazamox. This study characterizes ALS genes and extends our knowledge into the ALS resistance mechanisms involved in L. multiflorum. It also deepens our understanding of the complex diversification resistance mechanisms, thereby facilitating advances in weed resistance management strategies in wheat fields.

Effect of hydrogen bonding strength on the structure and properties of phase-separated hydrogel from gelatin

Dynamic bonded tough hydrogels often contain phase-separated structures that facilitate multiscale energy dissipation. However, the influence of bonding strength on the phase-separated structures and properties of hydrogels has been understudied. In this work, the hydrogen bonding strength within phase-separated gelatin/acrylic acid copolymer hydrogels was modulated by varying the methyl group content in the acrylic acid copolymer. It was found the mechanical properties of the hydrogels are determined by a synergistic effect between water content and hydrogen bond strength. Both weak and strong hydrogen bonds resulted in the hydrogel with high water content and low mechanical strength. It was observed that the chain dense regions within the hydrogels became more condensed and larger with increasing hydrogen bonding strength. The high water content in gels with strong hydrogen bonds is attributed to the formation of condensed chain dense regions, which prevent significant shrinkage of the hydrogel. The combination of high water content and condensed chain dense regions resulted in sparse chain loose regions within the hydrogel, which provided water channels for ion transport, enabling high ionic conductivity even at a reduced water content of 28.9 wt%.

Molecular dynamics simulation of extraction of Curcuma longa L. extract using subcritical water

Humans have utilized plants for various purposes, including sustenance and medical treatment for millennia. Researchers have extensively investigated medicinal plants’ potential in drug development, spurred by their rich array of chemical compounds. Curcumin, a valuable bioactive compound, is extracted from Turmeric, known by the scientific name Curcuma Longa L. Notably, curcumin boasts potent antioxidant and anti-inflammatory properties, making it a promising candidate for treating cancer and other microbial diseases. Therefore, the simulation study of the extraction of this important medicinal compound by water, which is a green solvent, was carried out. This study employed molecular dynamics simulation for the first time to explore the extraction of Curcuma Longa L. extract using subcritical water. The simulations were carried out at constant pressure and different temperatures, using the Compass force field in the Lammps simulation package. The findings revealed an increase in the amount of Curcuma longa extract with rising temperature, indicating a weakening of hydrogen bonds in water molecules. Water lost its polar state with increasing temperature and became a suitable non-polar solvent for extracting non-polar compounds. The average absolute relative deviation (AARD) for calculated and simulated density data was 6.45%.

Strong Replaces Weak: ​Hydrogen Bond‐Anchored Electrolyte Enabling Ultra‐Stable and Wide‐Temperature Aqueous Zinc‐Ion Capacitors

Despite aqueous electrolytes offer a great opportunity for large‐scale energy storage owing to their safety and cost‐effectiveness, their practical application suffers from the parasitic side reactions and poor temperature adaptability stemming from weak hydrogen‐bond (HB) network in free water. Here, we propose the guiding thought “strong replaces weak” to design hydrogen bond‐anchored electrolyte by introducing sulfolane (SL) for disrupting the regular weak HB network and contributing to superior temperature tolerance. Judiciously combined experimental characterization and theoretical calculation confirm that SL can remodel the primary solvation shell of metal ions, customize stable electrode interface chemistry and restrain the side reactions. Consequently, symmetric supercapacitor constructed by activated carbon (AC) electrodes is able to fully work within a voltage range of 2.4 V and reach high capacitance retention of 89.8% after 60000 cycles. Additionally, Zn anodes exhibit ultra‐stable Zn plating/stripping behaviors and a wide temperature range (‐20 ~ 60 °C), and zinc‐ion capacitor (Zn//AC) also delivers an excellent cycling stability with capacity retention of 99.7% after 55000 cycles, implying that the designed electrolyte has practical application potential in extreme environments. This work proposes a novel critical solvation strategy that paves the route for the construction of ultra‐stable and wide‐temperature aqueous energy storage devices.

Cross-linked Arenga pinnata (Wurmb.) Merr. starch and chitosan with sodium trimetaphosphate: Structure, physicochemical properties and in vitro digestibility.

The inherent limitations of native starch considerably restrict its applications in the food industry. To enhance its processing properties, Arenga pinnata (Wurmb.) Merr. starch (APS) was subjected to dual modification with low levels of sodium trimetaphosphate (0%, 1%, and 3%) and chitosan (1%) to investigate its physicochemical, thermal, pasting, and in vitro digestibility. The dual modification of APS significantly increased the degree of cross-linked (CLD) to 84.69%, resulting in a rougher surface texture. This process led to the formation of phosphate bonds, the weakening of hydrogen bonds, and a decrease in relative crystallinity, all while preserving the starch's crystalline structure. Additionally, the modification impeded paste formation, reduced swelling power, and lowered pasting enthalpy, while increasing the content of slowly digestible starch and resistant starch. These findings provided a basis to enhance the functional properties of starch-based materials, which could be applied to improve the texture and stability of food products such as sauces, dressings, and desserts in the food industry.

Iron Selenide Intercalated by Uncharged Molecules: Superconductivity in FeSe(C2H7NO)0.3

AbstractThe charge‐neutral intercalated iron selenide compound FeSe(C2H7NO)0.3 is formed from FeSe(C2H8N2)0.3 through amine exchange under solvothermal conditions. Although the exchanged molecules are of similar size, the distance of the FeSe‐layers increases from 10.68 Å to 13.58 Å. The combination of X‐ray diffraction and DFT calculations suggests a chemically reasonable, albeit somewhat simplified, model for the orientation of the molecules between the FeSe‐layers, which interact via weak hydrogen bonds. The neutral guest species is unable to transfer charge to the FeSe layers, which remain electronically undoped. While the starting compound is non‐superconducting, the resulting product exhibits a transition to superconductivity at Tc=14 K. The topology of the calculated Fermi surface undergoes only minimal alteration with increased layer spacing, a change that is considerably less pronounced than that observed with electron doping. Our findings indicate that undoped FeSe layers become superconducting when the interlayer distance is sufficiently large, while the highest critical temperatures necessitate additional electron doping.

Bis(azido-κN 1)bis-(2,2'-di-pyridyl-amine-κ2 N 1,N 1')iron(II) monohydrate.

In the hydrated title complex, [Fe(dpa)2(N3)2]·H2O (dpa is 2,2'-di-pyridyl-amine, C10H9N3), the FeII ion is coordinated in a distorted octa-hedral manner by two neutral, chelating dpa ligands and two anionic, monodentate azide (N3 -) ions in a cis-configuration. Distortion results from different Fe-N bond lengths [2.1397 (13)-2.2254 (12) Å] and (N-Fe-N) cis [80.12 (4)-96.72 (5)°] and (N-Fe-N) trans [166.73 (4)-176.62 (5)°] bond angles. Hydrogen bonds exist between two symmetry-related water mol-ecules as hydrogen donors to the γ-N atoms of azido ligands of two adjacent iron complexes and as acceptors from the amide group of the dpa ligands of two additional iron complexes. The hydrogen-bonding pattern results in eight-membered ⋯H-O-H⋯N⋯ rings and a band-like arrangement of the mol-ecules involved. Additional, weaker hydrogen bonds between the α-N atom of the second azido ligand as acceptors and the amide groups of the second dpa ligands as donors cross-link neighboring bands to layers extending parallel to (001).

Simultaneous realization of efficient solar evaporation and electricity collection through dual regulation of chemical composition and pore channels

The solar-driven interfacial evaporation is a recently developed zero-energy technology for seawater desalination. However, the low evaporation rate poses a significant obstacle to its industrial application, and the collection of streaming potential formed during the evaporation process remains challenging. In this paper, we constructed a solar evaporator capable of simultaneously achieving efficient solar evaporation and electricity collection. Specifically, a double network structure hydrogel comprising polyvinyl alcohol (PVA) and TEMPO-oxidized cellulose nanoparticles nanofibers (TOCNFs) was fabricated using ice templating, with the addition of sodium lignosulfonate (SLS) to further modulate water distribution within the network. The incorporation of carbon nanotubes (CNTs) enabled the achievement of a PVA/TOCNFs/SLS (PTFS) gel-based solar evaporator. The strong electronegativity carried by the TOCNFs enhances the electrostatic repulsion in the PVA-TOCNFs network, thus improving the mechanical properties of PTFS evaporator. The introduction of SLS, which contains abundant sulfonate groups, provides certain antibacterial properties to PTFS evaporator. Due to the presence of numerous hydrophilic groups, both TOCNFs and SLS can form weak hydrogen bonds with water. Through the synergistic effect of TOCNFs and SLS, the latent heat of water in PTFS evaporator is reduced to 924 kJ kg−1, enabling an evaporation rate of 3.70 kg m−2h−1 under 1 sun irradiation. Owing to the smaller pore size relative to the Debye radius and the presence of electronegative functional groups within the pores of PTFS evaporators, an overlapping bilayer is formed when water flows through, resulting in an open-circuit voltage increase of up to 270 mV. The integration of high-efficiency solar evaporation with streaming potential collection presents a novel avenue for enhancing the utilization of solar energy.

Crystal structure and Hirshfeld surface analysis of the salt 2-iodoethylammonium iodide – a possible side product upon synthesis of hybrid perovskites

The title organic–inorganic hybrid salt, C2H7IN+·I−, is isotypic with its bromine analog, C2H7BrN+·Br− [Semenikhin et al. (2024). Acta Cryst. E80, 738–741]. Its asymmetric unit consists of one 2-iodoethylammonium cation and one iodide anion. The NH3 + group of the organic cation forms weak hydrogen bonds with four neighboring iodide anions, leading to the formation of supramolecular layers propagating parallel to the bc plane. Hirshfeld surface analysis reveals that the most important contribution to the crystal packing is from N—H...I interactions (63.8%). The crystal under investigation was twinned by a 180° rotation around [001].

Structural Changes of Water in Carboxymethyl Cellulose Nanofiber Hydrogels during Vapor Swelling and Drying.

Carboxymethyl cellulose nanofiber (CMCF) forms mechanically strong hydrogels via freeze cross-linking. We investigated the vapor swelling and drying processes of the freeze cross-linked CMCF hydrogels using infrared spectroscopy and X-ray diffraction. From the shifts of the O-H and C=O stretching modes, the structural changes of water and carboxymethyl celluloses (CMC) were analyzed. The results show that two types of bound water exist in CMCF hydrogels due to a difference in hydrophilicity between the amorphous and crystalline regions of CMCF. Bound water adsorbed on the amorphous region forms a strong hydrogen bond with dangling O-H or C=O bonds of CMC, whereas that adsorbed on the crystalline region has a weak hydrogen bond with the localized hydrophilic groups on the hydrophobic surface. Due to the difference in the hydrogen bonding strength of the two types of bound water, the vapor swelling process of water in CMCF hydrogels is classified into four stages. For the drying process, the residual water, which formed a strong hydrogen bond with the hydrophilic groups of the CMC, has effects on the CMCF structure. The present result suggests that the adsorption and desorption of water are important factors governing the physical and chemical properties of the CMCF hydrogels.

Quantum Chemical Model Calculations of Adhesion and Dissociation between Epoxy Resin and Si-Containing Molecules.

There is no doubt that when solid surfaces are modified, the functional groups and atoms directly bonded to solid atoms play a major role in adsorption interactions with molecules or resins. In this study, the adhesion and dissociation between epoxy resin and molecules containing Si atoms were analyzed. The analysis, conducted in contact with the solid surface of silicon, utilized quantum chemical calculations based on a molecular model. We compared some Si-containing molecular models to test quantum chemical calculations that contribute to the study of adhesion and dissociation between epoxy resins and solid surfaces somehow other than simple potential energy curve calculations. The AFIR (artificial force induced reaction) method, implemented in the GRRM (global reaction route mapping) program, was employed to separate an epoxy resin model molecule and three types of silicon compounds (Si(CH3)2(OH)2, Si(CH3)4, and (CH3)2SiF2) in three directions, determining their minimum dissociation energy when changing the applied energy by 2.5 kJ/mol. In systems with weak hydrogen bonds, such as Si(CH3)4 or (CH3)2SiF2, the energy required for dissociation was not large; however, in systems with strong hydrogen bonds, such as Si(CH3)2(OH)2, dissociation was more difficult in the vertical direction. Although anisotropy due to hydroxyl groups was calculated in the horizontal direction, dissociation remained relatively easy.

Polymeric Manganese(II) Acetate Derivatives: Syntheses, Crystal Structures and Magnetic Properties

AbstractThree novel polymeric Mn(II) acetate derivatives, identified as {[Mn2.5(OH)(CH3COO)4] ⋅ 0.5CH3OH ⋅ 0.5CH3CN}n (1), {[Mn3(CH3CO O)6] ⋅ 0.5CH3CN}n (2) and {Mn1.5K(CH3COO)4}n (3), have been successfully prepared by systematically adjusting the ratio of reactants and using the 2‐mercapto‐5‐methyl‐1,3,4‐thiadiazole (Hmmt) as the template agent. These three complexes can be regarded as the different crystalline forms of Mn(CH3COO)2 under different reaction conditions. Single‐crystal X‐ray diffraction analyses revealed that 1 and 2 feature the unique three‐dimensional (3D) framework. For 3, it displays a 2D structure, which is further assembled to form a 3D extended network via the weak hydrogen bond interactions. Magnetic studies confirmed that 1 and 2 show antiferromagnetic interactions, and 1 displays a long‐range ordering phase below the critical temperature (Tc) of 7.8 K. In addition, magnetisation data collected for 1–2 yield low magnetic entropy changes, which can be attributed to the strong antiferromagnetic interactions among the Mn(II) centres.

Comparative Assessment of Water Models in Protein-Glycan Interaction: Insights from Alchemical Free Energy Calculations and Molecular Dynamics Simulations.

Accurate computational simulations of protein-glycan dynamics are crucial for a comprehensive understanding of critical biological mechanisms, including host-pathogen interactions, immune system defenses, and intercellular communication. The accuracy of these simulations, including molecular dynamics (MD) simulation and alchemical free energy calculations, critically relies on the appropriate parameters, including the water model, because of the extensive hydrogen bonding with glycan hydroxyl groups. However, a systematic evaluation of water models' accuracy in simulating protein-glycan interaction at the molecular level is still lacking. In this study, we used full atomistic MD simulations and alchemical absolute binding free energy (ABFE) calculations to investigate the performance of five distinct water models in six protein-glycan complex systems. We evaluated water models' impact on structural dynamics and binding affinity through over 5.8 μs of simulation time per system. Our results reveal that most protein-glycan complexes are stable in the overall structural dynamics regardless of the water model used, while some show obvious fluctuations with specific water models. More importantly, we discover that the stability of the binding motif's conformation is dependent on the water model chosen when its residues form weak hydrogen bonds with the glycan. The water model also influences the conformational stability of the glycan in its bound state according to density functional theory (DFT) calculations. Using alchemical ABFE calculations, we find that the OPC water model exhibits exceptional consistency with experimental binding affinity data, whereas commonly used models such as TIP3P are less accurate. The findings demonstrate how different water models affect protein-glycan interactions and the accuracy of binding affinity calculations, which is crucial in developing therapeutic strategies targeting these interactions.

Synthesis, Crystal Structure and Antifungal Activity of (E)-1-(4-Methylbenzylidene)-4-(3-Isopropylphenyl) Thiosemicarbazone: Quantum Chemical and Experimental Studies.

A novel (E)-1-(4-methylbenzylidene)-4-(3-isopropylphenyl) thiosemicarbazone was synthesized in a one-pot four-step synthetic route. Fourier transform infrared spectroscopy (FTIR), 1H and 13C nuclear magnetic resonances (NMR), single-crystal X-ray diffraction, and UV-visible absorption spectroscopy were utilized to confirm the successful preparation of the title compound. Single-crystal data indicated that the intramolecular hydrogen bond N(3)-H(3)···N(1) and intermolecular hydrogen bond N(2)-H(2)···S(1) (1 - x, 1 - y, 1 - z) existed in the crystal structure and packing of the title compound. Besides the covalent interaction, the non-covalent weak intramolecular hydrogen bond N(3)-H(3)···N(1) discussed by atoms in molecules (AIM) theory also functioned in maintaining the title compound's crystal structure. The strong intermolecular hydrogen bond N(2)-H(2)···S(1) (1 - x, 1 - y, 1 - z) discussed by Hirshfeld surface analysis played a major role in maintaining the title compound's crystal packing. The local maximum and minimum electrostatic potential of the title compound was predicted by electrostatic potential (ESP) analysis. The UV-visible spectra and HOMO-LUMO analysis revealed that the title compound has a low ΔEHOMO-LUMO energy gap (3.86 eV), which implied its high chemical reactivity due to the easy occurrence of charge transfer interactions within the molecule. Molecular docking and in vitro antifungal assays evidenced that its antifungal activity is comparable to the reported pyrimethanil, indicating its usage as a potential candidate for future antifungal drugs.

Comparative QSAR and q-RASAR modeling for aquatic toxicity of organic chemicals to three trout species: O. Clarkii, S. Namaycush, and S. Fontinalis

Oncorhynchus clarkii, Salvelinus fontinalis, and Salvelinus namaycush are vital trout species in North America, crucial for maintaining ecological balance, economic stability, and human health. These species thrive in cold, unpolluted waters and are highly vulnerable to contaminants. Given the rapid proliferation of industrial organic chemicals, traditional in vivo toxicity testing methods are inadequate to ensure timely and comprehensive risk assessments. Therefore, we employed in silico tools, namely Quantitative Structure-Activity Relationship (QSAR) and Quantitative Read-Across Structure-Activity Relationship (q-RASAR), to efficiently predict the aquatic toxicity of chemicals. Utilizing acute median lethal concentration (LC50) data from the US EPA’s ToxValDB, we developed the first-ever species-specific QSAR and q-RASAR models. The q-RASAR models outperformed traditional QSAR models by achieving higher internal and external statistical quality for each species. Key toxicity-determining descriptors included electrotopological state indices, autocorrelation descriptors, and similarity-based RASAR descriptors. For O. clarkii, the presence of chlorine atoms and rotatable bonds significantly influenced toxicity. S. fontinalis toxicity was strongly affected by polarizability, and van der Waals volumes, while S. namaycush showed sensitivity to weak hydrogen bond acceptors and topological complexity. The models predicted the toxicity of 1172 external compounds, identifying the most and least toxic chemicals for each species. This study not only offers the first comprehensive q-RASAR models for predicting trout species-specific toxicity but also provides novel insights into species-specific toxicological modes of action. The results contribute significantly to chemical screening and prioritization in aquatic risk assessments, effectively filling critical data gaps and advancing predictive modeling techniques.