Intermolecular hydrogen bonding behavior of amino acid radical cations.

Amino acid and peptide radicals are of broad interest due to their roles in biochemical oxidative damage, pathogenesis and protein radical catalysis, among others. Using density functional theory (DFT) calculations at the ωB97X-D/def2-QZVPPD//ωB97X-D/def2-TZVPP level of theory, we systematically investigated the hydrogen bonding between water and fourteen α-amino acids (Ala, Asn, Cys, Gln, Gly, His, Met, Phe, Pro, Sel, Ser, Thr, Trp, and Tyr) in both neutral and radical cation forms. For all amino acids surveyed, stronger hydrogen-bonding interactions with water were observed upon single-electron oxidation, with the greatest increases in hydrogen-bonding strength occurring in Gly, Ala and His. We demonstrate that the side chain has a significant impact on the most favorable hydrogen-bonding modes experienced by amino acid radical cations. Our computations also explored the fragmentation of amino acid radical cations through the loss of a COOH radical facilitated by hydrogen bonding. The most favorable pathways provided stabilization of the resulting cationic fragments through hydrogen bonding, resulting in more favorable thermodynamics for the fragmentation process. These results indicate that non-covalent interactions with the environment have a profound impact on the structure and chemical fate of oxidized amino acids.

Phenazine Cations as Anticancer Theranostics†.

The biological properties of two water-soluble organic cations based on polypyridyl structures commonly used as ligands for photoactive transition metal complexes designed to interact with biomolecules are investigated. A cytotoxicity screen employing a small panel of cell lines reveals that both cations show cytotoxicity toward cancer cells but show reduced cytotoxicity to noncancerous HEK293 cells with the more extended system being notably more active. Although it is not a singlet oxygen sensitizer, the more active cation also displayed enhanced potency on irradiation with visible light, making it active at nanomolar concentrations. Using the intrinsic luminescence of the cations, their cellular uptake was investigated in more detail, revealing that the active compound is more readily internalized than its less lipophilic analogue. Colocalization studies with established cell probes reveal that the active cation predominantly localizes within lysosomes and that irradiation leads to the disruption of mitochondrial structure and function. Stimulated emission depletion (STED) nanoscopy and transmission electron microscopy (TEM) imaging reveal that treatment results in distinct lysosomal swelling and extensive cellular vacuolization. Further imaging-based studies confirm that treatment with the active cation induces lysosomal membrane permeabilization, which triggers lysosome-dependent cell-death due to both necrosis and caspase-dependent apoptosis. A preliminary toxicity screen in the Galleria melonella animal model was carried out on both cations and revealed no detectable toxicity up to concentrations of 80 mg/kg. Taken together, these studies indicate that this class of synthetically easy-to-access photoactive compounds offers potential as novel therapeutic leads.

Empowering powdered activated carbon (PAC) with 3D printing: Achieving highly efficient and reusable cationic dye removal.

Powdered activated carbon (PAC) has been extensively used as an effective adsorbent. Despite its excellent adsorption ability, PAC has drawbacks, including difficulty in filtration and reactivation after use, limitations of mass transfer in deeper areas because of its aggregated powder form, and limited applicability in high-flow systems. To overcome these limitations, we used a three-dimensional (3D) printing system to fabricate PAC into a 3D structure. Spectral and microscopic analyses indicated that PAC was embedded into 3D monolith and exhibited high porosity suitable for facile mass transfer. The designed 3D PAC filter effectively removed 200 ppm-methylene blue (MB) within 8 h and showed an adsorption efficiency of 93.4 ± 0.9%. The adsorption of MB onto the 3D PAC filter was described by the pseudo-first-order kinetic and Freundlich isotherm models. The negatively charged 3D PAC filter might attract the positively charged MB, thus favoring the physical adsorption of MB onto the 3D PAC filter. The adsorption performance of the 3D PAC filter was tested at various pH levels of 4-10 and against MB spiked in seawaters and freshwaters to evaluate its feasibility for use in real environments. Finally, the reproducibility and reusability of the 3D PAC filter were demonstrated through repeated adsorption and desorption processes against MB.

Fabrication and application of a continuously regenerated cationic impurity removal device for ion chromatography.

A continuously regenerated cationic impurity removal device (CR-CRD) has been fabricated and applied for ion chromatography (IC). The removal of cationic impurities is realized by electrodialytically replacing the cationic impurities with hydronium ions. The device is configured in a sandwich structure and the central eluent channel is respectively isolated from both electrodes by stacked cation exchange membranes and a bipolar membrane (BPM) plus stacked anion exchange membranes. The eluent channel is packed with cation exchange resins in hydronium form and their continuous regeneration can be achieved by electrodialysis. A desirable feature of the device is gas-free, and no degasser is required. It showed sufficient ability to remove cationic impurities, as indicated by > 99.9 % removal of 10 mL of 1 mM LiOH solution injected (∼10 µmol) or continuous removal of 1 mM LiOH solution at the flow rate of 1 mL/min (1 µmol/min). A useful application was for sample pretreatment in nuclear power industry, by eliminating strong matrix interference of the sample containing LiOH (1 mM) and boric acid (2000 mg/L) with trace anion analysis.

New Insights into the Hygroscopic Character of Ionic Liquids: Study of Fourteen Representatives of Five Cation and Four Anion Families.

Over the past three decades, the synthesis of new ionic liquids (ILs) and the expansion of their use in newer applications have grown exponentially. From the beginning of this vertiginous period, it was known that many of them were hygroscopic, which in some cases limited their use or altered the value of their measured physical properties with all the problems that this entails. In an earlier article, we addressed the hygroscopic grade achieved by the ILs 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium methyl sulfate, 1-ethyl-3-methylimidazolium ethyl sulfate, 1-ethyl-3-methylpyridinium ethyl sulfate, 1-ethyl-3-methylimidazolium tosylate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-dodecyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylpyridinium tetrafluoroborate, 1-butyl-1-methylpiperidinium bis(trifluoromethyl sulfonyl)imide, 1-methyl-1-propylpyrrolidinium bis(trifluoromethyl sulfonyl)imide, 1-butyl-1-methylpyrrolidinium bis(trifluoromethyl sulfonyl)imide, and methyl trioctyl ammonium bis(trifluoromethyl sulfonyl)imide. The objective was to determine the influence of the chemical nature of the compounds, exposed surface area, sample volume, agitation, and temperature. For this purpose, we exposed the samples to abrupt increases in relative humidity from 15 to 100% for days in an atmosphere chamber and then proceeded with the reverse process in a gentle manner. The results show that the sorption of water from the atmosphere depends on the nature of the IL, especially the anion, with the chloride anion being of particular importance (chloride ≫ alkyl sulfates~bromide > tosylate ≫ tetrafluoroborate). It has also been proven for the EMIM-ES and EMIM-BF4 samples that the mechanism of moisture capture is both absorption and adsorption, and that the smaller the exposed surface area, the higher the ratio of the mass of water per unit area.

Structure- and Cation-Dependent Mechanism of Interaction of Tricyclic Antidepressants with NMDA Receptor According to Molecular Modeling Data.

Some tricyclic antidepressants (TCAs), including amitriptyline (ATL), clomipramine (CLO), and desipramine (DES), are known to be effective for management of neuropathic pain. It was previously determined that ATL, CLO, and DES are capable of voltage-dependent blocking of NMDA receptors of glutamate (NMDAR), which play a key role in pathogenesis of neuropathic pain. Despite the similar structure of ATL, CLO, and DES, efficacy of their interaction with NMDAR varies significantly. In the study presented here, we applied molecular modeling methods to investigate the mechanism of binding of ATL, CLO, and DES to NMDAR and to identify structural features of the drugs that determine their inhibitory activity against NMDAR. Molecular docking of the studied TCAs into the NMDAR channel was performed. Conformational behavior of the obtained complexes in the lipid bilayer was simulated by the method of molecular dynamics (MD). A single binding site (upper) for the tertiary amines ATL and CLO and two binding sites (upper and lower) for the secondary amine DES were identified inside the NMDAR channel. The upper and lower binding sites are located along the channel axis at different distances from the extracellular side of the plasma membrane. MD simulation revealed that the position of DES in the lower site is stabilized only in the presence of sodium cation inside the NMDAR channel. DES binds more strongly to NMDAR compared to ATL and CLO due to simultaneous interaction of two hydrogen atoms of its cationic group with the asparagine residues of the ion pore of the receptor. This feature may be responsible for the stronger side effects of DES. It has been hypothesized that ATL binds to NMDAR less efficiently compared to DES and CLO due to its lower conformational mobility. The identified features of the structure- and cation-dependent mechanism of interaction between TCAs and NMDAR will help in the further development of effective and safe analgesic therapy.

Cationic nanocarriers: A potential approach for targeting negatively charged cancer cell.

Cancer, a widespread and lethal disease, necessitates precise therapeutic interventions to mitigate its devastating impact. While conventional chemotherapy remains a cornerstone of cancer treatment, its lack of specificity towards cancer cells results in collateral damage to healthy tissues, leading to adverse effects. Thus, the quest for targeted strategies has emerged as a critical focus in cancer research. This review explores the development of innovative targeting methods utilizing novel drug delivery systems tailored to recognize and effectively engage cancer cells. Cancer cells exhibit morphological and metabolic traits, including irregular morphology, unchecked proliferation, metabolic shifts, genetic instability, and a higher negative charge, which serve as effective targeting cues. Central to these strategies is the exploitation of the unique negative charge characteristic of cancer cells, attributed to alterations in phospholipid composition and the Warburg effect. Leveraging this distinct feature, researchers have devised cationic carrier systems capable of enhancing the specificity of therapeutic agents towards cancer cells. The review delineates the underlying causes of the negative charge in cancer cells and elucidates various targeting approaches employing cationic compounds for drug delivery systems. Furthermore, it delves into the methods employed for the preparation of these systems. Beyond cancer treatment, the review also underscores the multifaceted applications of cationic carrier systems, encompassing protein and peptide delivery, imaging, photodynamic therapy, gene delivery, and antimicrobial applications. This comprehensive exploration underscores the potential of cationic carrier systems as versatile tools in the fight against cancer and beyond.

Co-impacts of cation type and humic acid on migration of polystyrene microplastics in saturated porous media.

The aging process of microplastics (MPs) could significantly change their physical and chemical characteristics and impact their migration behavior in soil. However, the complex effects of different cations and humic acids (HA) on the migration of aged MPs through saturated media are not clear. In this research, the migration and retention of pristine/aged PSMPs (polystyrene microplastics) under combined effects of cations (Na+, Ca2+) (ionic strength = 10 mM) and HA (0, 5, 15 mg/L) were investigated and analyzed in conjunction with the two-site kinetic retention model and DLVO theory. The findings showed that the aging process accelerated PSMPs migration under all tested conditions. Aged PSMPs were less susceptible to Ca2+ than pristine PSMPs. Under Ca2+ conditions, pristine/aged PSMPs showed higher retention than under Na+ conditions in the absence of HA. Furthermore, under Na+ conditions, the migration of aged PSMPs significantly increased at higher concentrations of HA. However, under Ca2+ conditions, the migration of aged PSMPs decreased significantly at higher concentrations of HA. In higher HA conditions, HA, Ca2+, and PSMPs interact to cause larger aggregations, resulting in the sedimentation of aged PSMPs. The DLVO calculations and two-site kinetic retention models' results showed the detention of PSMPs was irreversible under higher HA conditions (15 mg/L) with Ca2+, and aged PSMPs were more susceptible to clogging. These findings may help to understand the potential risk of migration behavior of PSMPs in the soil-groundwater environment.

Sewer sediment adhesion degeneration and gelatinous biopolymer deconstruction by structural cation chelation and alkaline macromolecule hydrolysis for improving hydraulic erosion.

Sediment siltation has been regarded as the serious challenge in sewer system, which dominantly root in the gelatinous extracellular polymeric substance (EPS) structure and cohesive ability. Considering the crucial roles of divalent cation bridging and macromolecular biopolymer winding in sediment EPS formation and adhesive behavior, an innovative combination strategy of sodium pyrophosphate (SP)-mediated divalent cation chelation and alkaline biopolymer hydrolysis was developed to degenerate sediment adhesion. At the SP dosage of 0.25 g/g TS and the alkaline pH 12, the SP + pH 12 treatment triggered structural transformation of aromatic proteins (α-helix to ß-turn) and functional group shifts of macromolecular biopolymers. In this case, the deconstruction and outward dissolution of gelatinous biopolymers were achievable, including proteins (tyrosine-like proteins, tryptophan-like proteins), humic acids, fulvic acids, polysaccharides and various soluble microbial products. These were identified as the major driving forces for sediment EPS matrix disintegration and bio-aggregation deflocculation. The extraction EPS content was obviously increased by 18.88 mg COD/g TS. The sediment adhesion was sensitive to EPS matrix damage and gelatinous biopolymer deconstruction, leading to considerable average adhesion degeneration to 0.98 nN with reduction rate of 78.32%. As such, the sediments could be disrupted into dispersive fragments with increased surface electronegativity and electric repulsion (up to -45.6 mV), thereby the sediment resistance to hydraulic erosion was impaired, providing feasibility for in-situ sediment floating and removal by gravity sewage flow in sewer.

Formation of cation bridges and its promoting mechanism for sorption of sulfamethoxazole by montmorillonite.

The coexistence of metal cations is often accompanied by organic pollution and could affect the environmental fate of organics by mediating the formation of cation bridges. However, the environmental fate and risk of organics in cation co-existing environments are poorly understood due to the lack of accurate identification of cation bridge formation and stability. In this study, the sorption of sulfamethoxazole (SMX) on montmorillonite (MT) with the coexistence of three different valence metal cations (Na+, Ca2+, and Cr3+) was investigated. Ca2+ and Cr3+ can significantly promote the sorption of SMX on MT for about 5∼10 times promotion, respectively, while Na+ bridges displayed little effect on the sorption of SMX. The sorption binding energy of SMX with MT-Ca (-44.01 kcal/mol) and MT-Cr (-64.57 kcal/mol) bridges was significantly lower than that with MT-Na (-38.45 kcal/mol) and MT (-39.39 kcal/mol), indicating that the sorption affinity of SMX on Cr and Ca bridges was much stronger. The higher valence of the cations also resulted in a more stable adsorbed SMX with less desorption fluctuation. In addition, the relatively higher initial concentration of SMX and the valence of cations increased the bonding density of the cation bridges, thus promoting the apparent sorption of SMX on MT to a certain extent. This work reveals the formation and function of cation bridges in the sorption of SMX on MT. It lays a theoretical foundation for further understanding the environmental fate and risk of organics.

Integration of metal organic framework nanoparticles into sodium alginate biopolymer-based three-dimensional membrane capsules for the efficient removal of toxic metal cations from water and real sewage.

Sodium alginate (SA) biopolymer has been recognized as an efficient adsorbent material owing to their unique characteristics, including biodegradability, non-toxic nature, and presence of abundant hydrophilic functional groups. Accordingly, in the current research work, UiO-66-OH and UiO-66-(OH)2 metal organic framework (MOF) nanoparticles (NPs) have been integrated into SA biopolymer-based three-dimensional (3-D) membrane capsules (MCs) via a simple and facile approach to remove toxic metal cations (Cu2+ and Cd2+) from water and real sewage. The newly configured capsules were characterized by FTIR, SEM, XRD, EDX and XPS analyses techniques. Exceptional sorption properties of the as-developed capsules were ensured by evaluation of the pertinent operational parameters, i.e., contents of MOF-NPs (1-100 wt%), adsorbent dosage (0.001-0.05 g), content time (0-360 h), pH (1-8), initial concentration of metal cations (5-1000 mg/L) and reaction temperature (298.15-333.15 K) on the eradication of Cu2+ and Cd2+ metal cations. It was found that hydrophilic functional groups (-OH and -COOH) have performed an imperative role in the smooth loading of MOF-NPs into 3-D membrane capsules via intra/inter-molecular hydrogen bonding and van der waals potencies. The maximum monolayer uptake capacities (as calculated by the Langmuir isotherm model) of Cd2+ and Cu2+ by 3-D SGMMCs-OH were 940 and 1150 mg/g, respectively, and by 3-D SGMMCs-(OH)2 were 1375 and 1575 mg/g, respectively, under optimum conditions. The as-developed capsules have demonstrated superior selectivity against targeted metal cations under designated pH and maintained >80 % removal efficiency up to six consecutive treatment cycles. Removal mechanisms of metal cations by the 3-D SGMMCs-OH/(OH)2 was proposed, and electrostatic interaction, ion-exchange, inner-sphere coordination bonds/interactions, and aromatic ligands exchange were observed to be the key removal mechanisms. Notably, FTIR and XPS analysis indicated that hydroxyl groups of Zr-OH and BDC-OH/(OH)2 aromatic linkers played vital roles in Cu2+ and Cd2+ adsorption by participating in inner-sphere coordination interactions and aromatic ligands exchange mechanisms. The as-prepared capsules indicated >70 % removal efficiency of Cu2+ from real electroplating wastewater in the manifestation of other competitive metal ions and pollutants under selected experimental conditions. Thus, it was observed that newly configured 3-D SGMMCs-OH/(OH)2 have offered a valuable discernment into the development of MOFs-based water decontamination 3-D capsules for industrial applications.

Structural and tribological studies on the interaction of porcine gastric mucin with non- and cationic-modified ß-lactoglobulins.

ß-lactoglobulin (BLG) is the major whey protein with negative charges at neutral pH in aqueous media. Thus, the interaction with mucins, the major polyanionic component of mucus, is very weak due to the electrostatic repulsion between them. The present study postulates that cationization of BLG molecules may reverse the interaction characteristics between BLG and mucin from repulsive to associative. To this end, cationic-modified BLGs were prepared by grafting positively charged ethylenediamine (EDA) moieties into the negatively charged carboxyl groups on the aspartic and glutamic acid residues and compared with non-modified BLG upon mixing with porcine gastric mucin (PGM). To characterize the structural and conformational features of PGM, non/cationized BLGs, and their mixtures, various spectroscopic approaches, including zeta potential, dynamic light scattering (DLS), and circular dichroism (CD) spectroscopy were employed. Importantly, we have taken surface adsorption with optical waveguide lightmode spectroscopy (OWLS), and tribological properties with pin-on-disk tribometry at the sliding interface as the key approaches to determine the interaction nature between them as mixing PGM with polycations can lead to synergistic lubrication at the nonpolar substrate in neutral aqueous media as a result of an electrostatic association. All the spectroscopic studies and a substantial improvement in lubricity collectively supported a tenacious and associative interaction between PGM and cationized BLGs, but not between PGM and non-modified BLG. This study demonstrates a unique and successful approach to intensify the interaction between BLG and mucins, which is meaningful for a broad range of disciplines, including food science, macromolecular interactions, and biolubrication etc.

Negative Electron Transfer Collision-Induced Dissociation of G-Quadruplexes: Uncovering the Guanine Radical Anion Loss Pathway.

G-quadruplex (G4) DNA can form highly stable secondary structures in the presence of metal cations, and research has shown its potential as a transcriptional regulator for oncogenes in the human genome. In order to explore the interactions of DNA with metal cations using mass spectrometry, employing complementary fragmentation methods can enhance structural information. This study explores the use of ion-ion reactions for sequential negative electron transfer collision-induced dissociation (nET-CID) as a complement to traditional ion-trap CID (IT-CID). The resulting nET-CID data for G4 anions with and without metal cations show an increase in fragment ion type diversity and yield of structurally informative ions relative to IT-CID. The nET-CID yields greater sequence coverage by virtue of fragmentation at the 3'-side of thymine residues, which is lacking with IT-CID. Potassium adductions to backbone fragments in IT-CID and nET-CID spectra were nearly identical. Of note is a prominent fragment resulting from a loss of a 149 Da anion seen in nET-CID of large, G-rich sequences, proposed to be radical anion guanine loss. Neutral loss of neutral guanine (151 Da) and deprotonated nucleobase loss (150 Da) have been previously reported, but this is the first report of radical anion guanine loss (149 Da). Confirmation of the identity of the 149 Da anion results from the examination of the homonucleobase sequence 5'-GGGGGGGG-3'. Loss of a charged adenine radical anion at much lower relative abundance was also noted for the sequence 5'-AAAAAAAA-3'. DFT modeling indicates that the loss of a nucleobase as a radical anion from odd-electron nucleic acid anions is a thermodynamically favorable fragmentation pathway for G.

Impacts of cationic lipid-DNA complexes on immune cells and hematopoietic cells in vivo.

The inability to systemic administration of nanoparticles, particularly cationic nanoparticles, has been a significant barrier to their clinical translation due to toxicity concerns. Understanding the in vivo behavior of cationic lipids is crucial, given their potential impact on critical biological components such as immune cells and hematopoietic stem cells (HSC). These cells are essential for maintaining the body's homeostasis, and their interaction with cationic lipids is a key factor in determining the safety and efficacy of these nanoparticles. In this study, we focused on the cytotoxic effects of cationic lipid/DNA complexes (CLN/DNA). Significantly, we observed that the most substantial cytotoxic effects, including a marked increase in numbers of long-term hematopoietic stem cells (LT-HSC), occurred 24 h post-CLN/DNA treatment in mice. Furthermore, we found that CLN/DNA-induced HSC expansion in bone marrow (BM) led to a notable decrease in the ability to reestablish blood cell production. Our study provides crucial insights into the interaction between cationic lipids and vital cellular components of the immune and hematopoietic systems.

Surfactant-based supramolecular dye assembly: A highly selective and economically viable platform for quantification of heparin antidote.

Herein, we have employed a supramolecular assembly of a cationic dye, LDS-698 and a common surfactant sodium dodecyl sulfate (SDS) as a turn-on fluorescent sensor for protamine (Pr) detection. Addition of cationic Pr to the solution of dye-surfactant complex brings negatively charged SDS molecules together through strong electrostatic interaction, assisting aggregation of SDS way before its critical micellar concentration (CMC). These aggregates encapsulate the dye molecules within their hydrophobic region, arresting non-radiative decay channels of the excited dye. Thus, the LDS-698•SDS assembly displays substantial enhancement in fluorescence intensity that follows a nice linear trend with Pr concentration, providing limit of detection (LOD) for Pr as low as 3.84(±0.11) nM in buffer, 124.4(±6.7) nM in 1% human serum and 28.3(±0.5) nM in 100% human urine. Furthermore, high selectivity, low background signal, large stokes shift, and emission in the biologically favorable deep-red region make the studied assembly a promising platform for Pr sensing. As of our knowledge it is the first ever Pr sensory platform, using a very common surfactant (SDS), which is economically affordable and very easily available in the market. This innovative approach can replace the expensive, exotic and specialized chemicals considered for the purpose and thus showcase its potential in practical applications.

Oxidative cyclization reagents reveal tryptophan cation-π interactions.

Methods for selective covalent modification of amino acids on proteins can enable a diverse array of applications, spanning probes and modulators of protein function to proteomics1-3. Owing to their high nucleophilicity, cysteine and lysine residues are the most common points of attachment for protein bioconjugation chemistry through acid-base reactivity3,4. Here we report a redox-based strategy for bioconjugation of tryptophan, the rarest amino acid, using oxaziridine reagents that mimic oxidative cyclization reactions in indole-based alkaloid biosynthetic pathways to achieve highly efficient and specific tryptophan labelling. We establish the broad use of this method, termed tryptophan chemical ligation by cyclization (Trp-CLiC), for selectively appending payloads to tryptophan residues on peptides and proteins with reaction rates that rival traditional click reactions and enabling global profiling of hyper-reactive tryptophan sites across whole proteomes. Notably, these reagents reveal a systematic map of tryptophan residues that participate in cation-π interactions, including functional sites that can regulate protein-mediated phase-separation processes.

Dilation of ion selectivity filters in cation channels.

Ion channels establish the voltage gradient across cellular membranes by providing aqueous pathways for ions to selectively diffuse down their concentration gradients. The selectivity of any given channel for its favored ions has conventionally been viewed as a stable property, and in many cation channels, it is determined by an ion-selectivity filter within the external end of the ion-permeation pathway. In several instances, including voltage-activated K+ (Kv) channels, ATP-activated P2X receptor channels, and transient receptor potential (TRP) channels, the ion-permeation pathways have been proposed to dilate in response to persistent activation, dynamically altering ion permeation. Here, we discuss evidence for dynamic ion selectivity, examples where ion selectivity filters exhibit structural plasticity, and opportunities to fill gaps in our current understanding.

Evidence from experiments, modeling, and field observations for effects of increased salinization on re-distribution of sediment base cations in Taihu Lake, China.

Taihu Lake, the third largest freshwater lake in China, has experienced rapid salinization in the past decades; however, little is known about the impact of sodium (Na) on ion exchange in the lake environment. To explore the potential effect of increased Na on the migration of base cations (Ca and Mg) and resulting redistribution between the water and sediment, we used the adsorption-exchange experiment, MINTEQ modeling to explore the cation exchange induced by high Na input, and its impact on the redistribution of Ca and Mg in Taihu different media. The results indicated that exchanged quantity of Ca and Mg increased with time, and the exchange process reached 90% during 0-4 h and reached equilibrium after 24 h under 100 mg/L Na (the maximum Na concentration in Taihu sediment pore water). Our MINTEQ modeled result indicated that the exchanged quantity of Ca and Mg increased with the increasing Na concentration, with Ca being preferably exchanged over Mg at the same Na concentration. The MINTEQ model further predicted that, in the Taihu lake environment, the exchange adsorption would reach the equilibrium at the concentration of 6000 mg/L Na, with exchanged Ca2+ and Mg2+ accounting for 47% and 55% of the total exchangeable Ca and Mg in the sediment, respectively. Although current Na-induced exchange in the Taihu lake has been far from the equilibrium, the MINTEQ result confirmed the existence of this reaction and predicted the potential redistribution of base cations or Ca/Mg ratio in the lake sediment and water phase with further Na increase. Furthermore, our field observations not only confirmed the existence of Na-induced cation exchange in this lake environment but also were generally in agreement with our experimental and modeled results. The increased salinization-induced ion exchange would alter the re-distribution of base cations and the resulting potential ecosystem consequences should be given close attention in this large freshwater lake.

New biologically active ionic liquids with benzethonium cation-efficient SAR inducers and antimicrobial agents.

BACKGROUND: An urgent need to find new methods for crop protection remains open due to the withdrawal from the market of the most toxic pesticides and increasing consumer awareness. One of the alternatives that can be used in modern agriculture is the use of bifunctional compounds whose actions towards plant protection are wider than those of conventional pesticides. RESULTS: In this study, we present the investigation of the biological efficacy of nine dual-functional salts containing a systemic acquired resistance (SAR)-inducing anion and the benzethonium cation. A significant result of the presented study is the discovery of the SAR induction activity of benzethonium chloride, which was previously reported only as an antimicrobial agent. Moreover, the concept of dual functionality was proven, as the application of presented compounds in a given concentrations resulted both in the control of human and plant bacteria species and induction of SAR. CONCLUSION: The strategy presented in this article shows the capabilities of derivatization of common biologically active compounds into their ionic derivatives to obtain bifunctional salts. This approach may be an example of the design of potential new compounds for modern agriculture. It provides plants with two complementary actions allowing to provide efficient protection to plants, if one mode of action is ineffective. © 2024 Society of Chemical Industry.

Tracing the Antibacterial Performance of Bis-Imidazolium-based Ionic Liquid Derivatives.

Ionic liquid (IL) cationic species have recently captivated the attention of pharmacists, biochemists, and biomedical scientists as promising antibacterial agents to deal with the multidrug resistance bacteria crisis. The structure and functional groups of ILs influence their physiochemical properties and biological activities. However, a comprehensive study is required to fully understand the details of the antibacterial activity of ILs carrying various functional groups. Herein, dicationic ILs (DCILs) are reported based on imidazolium rings as efficient antibacterial agents. The DCILs carried various functionalities such as 2-hydroxybutyl (DCIL-1), 2-hydroxy-3-isopropoxypropyl (DCIL-2), 2-hydroxy-3-(methacryloyloxy)propyl (DCIL-3), 2-hydroxy-2-phenylethyl (DCIL-4), and 2-hydroxy-3-phenoxypropyl (DCIL-5). The structure-antibacterial activity relationships of the DCILs against Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) were comprehensively studied through antibacterial tests, morphology analysis, and adhesion tests. The experimental assays revealed an antibacterial efficacy order of DCIL-5 > DCIL-1 > DCIL-4 > DCIL-2 > DCIL-3. The all-atom molecular dynamics (MD) simulation showed a deep permeation of the hydrophobic -OPh functional group of DCIL-5 through the E. coli membrane model in agreement with the experimental observations. Current findings assist scientists in designing new task-specific DCILs for effective interactions with biological membranes for different applications.