Stacking Interactions Research Articles

COF-derived porous nitrogen-doped carbon for removal of emerging organic contaminants and efficient uranium extraction from seawater

The development of adsorbents for efficient and highly selective seawater extraction of uranium was instrumental in fostering sustainable progress in energy and addressing the prevailing energy crisis. However, the complex background composition of the marine environment, including radionuclides, organic pollutants, and a large number of co-existing heavy metal ions, were non-negligible obstacles to the extraction of uranium from seawater. The present investigation successfully employed a self-templated approach to synthesize porous nitrogen-doped carbon (PNC) derived from COF, which exhibited tremendous potential as an adsorbent for pollutant removal in environmental treatment. LZU1@PNC not only retained the structural features of the original COF-LZU1, but also overcame the acid-base instability problem commonly found in COFs. Subsequently, the removal process of two typical water pollutants on the material was investigated using 2,4-DCP and [UO2(CO3)3]4-. The results demonstrated that LZU1@PNC exhibited superior removal performance for the target pollutants compared to COF-LZU1, owing to its larger specific surface area and abundant defect structure. After six desorption-regeneration cycles, LZU1@PNC still maintained a high removal rate of the target contaminants, demonstrating the stability of this material and its excellent recyclability. In addition, based on various characterization techniques, the removal mechanism of 2,4-DCP was presumed to be mainly electrostatic attraction, hydrogen bonding, and π-π stacking interactions. Conversely, the elimination process of [UO2(CO3)3]4- predominantly relied on surface complexation phenomena. The present investigation provided new perspectives and stimulated a broader study of other COF-derived carbon materials and their modifications as adsorbents for uranium extraction from seawater and other applications.

A novel sensitization strategy for uncertain single stranded probe on electrode surface based on terminal deoxynucleotidyl transferase and G-rich spherical nucleic acids

In recent years, RPA-CRISPR/Cas12a-based electrochemical biosensors have emerged as highly effective tools for nucleic acid detection. However, the random trans-cleavage characteristics of Cas12a on single-stranded nucleic acid sequences can result in the presence of uncertain nucleic acid residues on the electrode surface post-reaction. This situation complicates subsequent sensitization strategies. In this study, we devised a universal sensitization protocol mediated by terminal deoxynucleotidyl transferase (TdT), a template-independent DNA polymerase and G-rich spherical nucleic acids (G-rich SNAs) with superior performance. Initially, Cas12a was activated by the specific RPA amplification product and cleaved the closed single stranded DNA (C-ssDNA) on the electrode surface. Then, the TdT enzyme extended residual single stranded DNA (R-ssDNA) on the electrode surface, forming G-Quadruplex structures. Subsequently, G-rich SNAs were immobilized on the electrode surface via π-π stacking interactions with the G-quadruplexes. Consequently, a substantial accumulation of hemin occurred within the G-quadruplex cluster structures, generating significant electrochemical signals. We applied this method to the trace detection of Staphylococcus aureus (S. aureus) and achieved a good linear calibration curve with concentrations ranging from 0 CFU/mL to 104 CFU/mL. Notably, the limit of detection (LOD) was as low as 1.29 CFU/mL, surpassing that of most similar sensors. These results demonstrate that our proposed universal sensitization method effectively addresses the limitations associated with the random trans-cleavage characteristics of Cas12a.

Preparation of an imidazolium-based poly(ionic liquid) functionalized magnetic three-dimensional graphene oxide for magnetic solid phase extraction of pyrethroids from tea samples

In this work, an imidazolium-based poly(ionic liquid) (poly(1-dodecyl-3-vinyl-imidazolium bromide) functionalized magnetic three-dimensional graphene oxide (Fe3O4@3D-GO@poly(ImC12+Br−)) was synthesized via a vacuum freezing-drying method and used as a magnetic solid phase extraction (MSPE) adsorbent for the efficient extraction of pyrethroid pesticides from tea samples. The prepared Fe3O4@3D-GO@poly(ImC12+Br−) was confirmed by scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FT-IR), vibrating sample magnetometer (VSM) and X-ray photoelectron spectrogram (XPS). Due to its large specific surface area and the ability to offer multiple intermolecular interactions, including π-π stacking, hydrophobic and hydrogen bond interactions, the prepared Fe3O4@3D-GO@poly(ImC12+Br−) showed high extraction efficiency for pyrethroids. The experimental parameters were optimized by a combination of single-factor method and Box-Behnken design to improve the extraction efficiency. Under the optimum conditions, coupled with high performance liquid chromatography (HPLC), a sensitive analytical method was developed for the determination of pyrethroids, and the proposed method showed wide linear ranges (1.00–100 μg L−1) with correlation coefficients (R) ranging from 0.9980 to 0.9994, low limits of detection (0.100 μg L−1) and good repeatability with intra-day relative standard deviations (RSDs) in the range of 2.90–5.53 % and inter-day RSDs in the range of 1.83–7.76 %. Moreover, the developed method was successfully applied to the determination of pyrethroids in tea samples and satisfactory recoveries ranging from 82.37 % to 114.34 % were obtained. The results showed that the developed Fe3O4@3D-GO@poly(ImC12+Br−) was an ideal, effective and selective material for the extraction and enrichment of pyrethroids from tea samples.

Construction of a Bifunctional Nanoelectrode for Intracellular Natural Product Delivery and Monitoring Anticancer Efficiency in Single Cells.

Natural products play a significant role in new drug discovery and anticancer therapy, making the evaluation of their anticancer efficiency crucial for clinical application. However, delivering natural products to single cells and in situ monitoring of induced signaling molecule fluctuation to evaluate anticancer efficiency remain significant challenges. Hence, we proposed a universal and straightforward strategy to construct a bifunctional nanoelectrode that integrates drug loading and monitoring of signal molecule fluctuations at the single-cell level. Platinum (Pt) nanoparticles/reduced graphene oxide (rGO) composites were first electrochemically deposited on the carbon fiber nanoelectrode (CFNE@Pt/rGO) to serve as electrocatalytic materials for the monitoring of natural-product-induced reactive oxygen species (ROS) generation. The GO/natural product complex, formed by π-π stacking and hydrophobic interactions, was further electrochemically reduced on the surface of CFNE@Pt/rGO to enable the CFNE drug-loading function. Using this bifunctional functional nanoelectrode, a series of natural products (such as capsaicin, curcumin, and chrysin) were delivered into single cancer cells, and their anticancer efficiency was evaluated by measuring ROS generation. The results showed that intracellular ROS production induced by chrysin was 1.5-fold greater than that of curcumin and 2.1-fold greater than that of capsaicin. This work proposes an effective tool to evaluate the anticancer efficiency of various natural products. Additionally, this nanotool can be expanded to monitor the fluctuation of other biomolecules (such as RNS, GSH, NADH, etc.) by replacing Pt nanoparticles with other electrocatalytic materials, which is significant for comprehensively exploring the anticancer efficiency of new drugs and for the clinical treatment of various diseases.

Mechanistic Insight into the Enantioselective Degradation of Esterase QeH to (R)/(S)-Quizalofop-Ethyl with Molecular Dynamics Simulation Using a Residue-Specific Force Field.

The enantioselective mechanism of the esterase QeH against the two enantiomers of quizalofop-ethyl (QE) has been primitively studied using computational and experimental approaches. However, it is still unclear how the esterase QeH adjusts its conformation to adapt to substrate binding and promote enzyme-substrate interactions in the catalytic kinetics. The equilibrium processes of enzyme-substrate interactions and catalytic dynamics were reproduced by performing independent molecular dynamics (MD) runs on the QeH-(R)/(S)-QE complexes with a newly developed residue-specific force field (RSFF2C). Our results indicated that the benzene ring of the (R)-QE structure can simultaneously form anion-π and cation-π interactions with the side-chain group of Glu328 and Arg384 in the binding cavity of the QeH-(R)-QE complex, resulting in (R)-QE being closer to its catalytic triplet system (Ser78-Lys81-Tyr189) with the distances measured for the hydroxyl oxygen atom of the catalytic Ser78 of QeH and the carbonyl carbon atom of (R)-QE of 7.39 Å, compared to the 8.87 Å for (S)-QE, whereas the (S)-QE structure can only form an anion-π interaction with the side chain of Glu328 in the QeH-(S)-QE complex, being less close to its catalytic site. The computational alanine scanning mutation (CAS) calculations further demonstrated that the π-π stacking interaction between the indole ring of Trp351 and the benzene ring of (R)/(S)-QE contributed a lot to the binding stability of the enzyme-substrate (QeH-(R)/(S)-QE). These results facilitate the understanding of their catalytic processes and provide new theoretical guidance for the directional design of other key enzymes for the initial degradation of aryloxyphenoxypropionate (AOPP) herbicides with higher catalytic efficiencies.

Novel 5-alkenylthiothiazolidinone scaffold discovery as Multi-Chitinases inhibitors to arrest the molting of Asian corn borer

Chitinases are crucial enzymes in insect growth and development processes and have thus become potential targets for the control of insect pests. Rhodanine (5-alkenylthiothiazolidinone) is an important fragment with various biological activities in agriculture. Therefore, 24 novel 5-alkenylthiothiazolidinone derivatives were designed and synthesized by introducing a hydrophobic hydrocarbon chain and a benzylformamide group on the basis of the conserved binding cavity of three chitinases, OfChtI, OfChtII and OfChi-h. These 5-alkenylthiothiazolidinone analogs were found for the first time to have inhibitory effects on OfChtII, except for their ability to inhibit the other two known chitinases, OfChtI and OfChi-h. The inhibitory activities of the target compounds against OfChtI and OfChi-h ranged from 40 % to 95 % at a concentration of 100 μM. In particular, some compounds were also found to have an inhibitory rate of 50 % against OfChtII. Among them, the Ki values of the most potent compound 5e-9 were 5.82, 27.5 and 6.77 μM against OfChtI, OfChtII and OfChi-h, respectively. The inhibition mechanism studies revealed that both π stacking interactions and hydrophobic interactions were vital for the binding of Compound 5e-9 with the three chitinases. A lethal and sublethal bioassay study revealed that Compound 5e-9 could affect the growth and development of Asian corn borers. This work suggested that 5-alkenylthiothiazolidinone could be a novel inhibitor scaffold against multichitinase for the development of insect growth regulators.

Conformational Locking Induced Enantioselective Diarylcarbene Insertion into B-H and O-H Bonds Using a Cationic Rh(I)/Diene Catalyst.

Transition-metal-catalyzed enantioselective transformations of aryl/aryl carbene are inherently challenging due to the difficulty in distinguishing between two arene rings in the reaction process thus remain largely less explored. The few successful examples reported so far, without exception, have all been catalyzed by Rh(II)-complexes. Herein, we describe our successful development of a novel cationic Rh(I)/chiral diene catalytic system capable of efficient enantioselective B-H and O-H insertions with diaryl diazomethanes, allowing the access to a broad range of gem-diarylmethine boranes and gem-diarylmethine ethers in good yields with high enantioselectivities. Notably, previously unattainable asymmetric diarylcarbene insertion into the O-H bond was achieved for the first time. A remarkable feature of this newly designed Rh(I)/diene catalyst bearing two ortho-amidophenyl substitutents is that it can distinguish between two arene rings of the diaryl carbene through a stereochemically selective control of π-π stacking interactions. DFT calculations indicate that the rotation-restricted conformation of Rh(I)/diene complex played an important role in the highly enantioselective carbene transformations. This work provides an interesting and unprecedented stereocontrol mode in diaryl metal carbene transformations.

Covalent Isothiocyanate Inhibitors of Macrophage Migration Inhibitory Factor as Potential Colorectal Cancer Treatments.

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine that has roles in innate and adaptive human immune responses, as well as inflammation. MIF exerts its biological activity by binding to the cell surface receptor CD74 as well as intracellular signalling proteins. MIF also possesses keto-enol tautomerase activity. Inhibition of the tautomerase activity has been associated with loss of biological activity of MIF and a potential anticancer target. Isothiocyanates (ITCs) are a class of compounds present in cruciferous vegetables that inhibit the MIF tautomerase activity via covalent modification of the N-terminal proline. A range of substituted ITCs featuring benzyl, phenethyl and phenyl propyl isothiocyanates were designed, synthesised and tested to determine any structure activity relationship for inhibiting MIF. Crystal structures of covalent compounds 8 and 9 in complex with rhMIF revealed key hydrogen bonding and edge-to-face π stacking interactions. Compound 9 and 11 with sub micromolar activity were tested in the NCI60 cancer cell lines panel. Both compounds showed tissue-specific reduced growth in colon and renal cancer cell lines, while one of these showed potent, dose-dependent inhibition of growth against all seven colon cancer cell lines (GI50<2.5 μM) and all eight renal cancer cell lines (GI50<2.2 μM).

Uncovering a general oxidation model of nitrogen-containing oxidant in N-heterocyclic carbene (NHC) catalyzed oxidative reactions of aldehydes

Predicting how oxidants interact with reactive partners to alter the oxidation mechanism is a significant challenge in carbene catalysis. In this study, we investigated several examples to address this issue. Using density functional theory (DFT), we explored N-heterocyclic carbene (NHC)-catalyzed oxidative [2 + 4] annulations of aliphatic aldehydes with α,β-unsaturated ketones, focusing on the role of nitrogen-containing oxidant. Our computational results reveal that a hydrogen-bonding bridge framework, formed during oxidation, is crucial for facilitating π···π stacking interactions between the oxidant and the NHC catalyst. These interactions significantly lower the oxidation energy barrier, enabling a facile hydride transfer. This mechanism was validated across other reactions involving different nitrogen-containing oxidants. Frontier molecular orbital (FMO) analysis demonstrates how the NHC catalyst lowers the cycloaddition energy barrier by altering the orbital overlap from shoulder-to-head to head-to-head. Additionally, this elucidates the origin of stereoselectivity by highlighting energy differences between two reacting components at cycloaddition transition states. The nucleophilic index further predicts the preferred ketone attack site. This work advances our understanding of oxidation mechanisms involving nitrogen-containing oxidants and offers valuable insights for designing potent organic oxidants in organocatalytic oxidative reactions.

Synthesis, characterization, and biological activity of a fresh class of sonochemically synthesized Cu2+ complexes

The synthesis and characterization of metal complexes have garnered significant attention due to their versatile applications in scientific and biomedical fields. In this research, two novel copper (Cu) complexes, [Cu(L)(L′)(H2O)2] (1) and [Cu(L)(Im)H2O] (2), where L = pyridine-2,6-dicarboxylic acid, L′ = 2,4-diamino-6-hydroxypyrimidine, and Im = imidazole, were investigated concerning their sonochemical synthesis, spectroscopic analysis, and biological activity. The complexes’ structural characterization was achieved using analytical techniques, including single-crystal X-ray structure determination, FTIR, PXRD, TGA and DTA, SEM, TEM, and EDS. Complex (1) displayed a six-coordinated Cu2+ ion, while complex (2) exhibited a five-coordinated Cu2+ ion. The crystal structures revealed monoclinic (C2/c) and triclinic (P-1) space groups, respectively. Both complexes showcased zero-dimensional (0D) supramolecular networks, primarily driven by hydrogen bonding and π–π stacking interactions, which played pivotal roles in stabilizing the structures and shaping the unique supramolecular architecture. Both complexes demonstrated significant antioxidant activity, suggesting their capability to neutralize free radicals and mitigate oxidative stress-related diseases. Hemolysis percentages were less than 2%, per the ASTM F756-00 standard, indicating non-hemolytic behavior. Low cytotoxicity was observed against fibroblast and MCF-7 cell lines. They do not exhibit antibacterial activity against Escherichia coli and Staphylococcus aureus. These findings suggest that the synthesized Cu2+‒complexes hold considerable promise for applications in drug delivery and cancer treatment. This research contributes to the advancement of supramolecular chemistry and the development of multifunctional materials for diverse scientific and medical applications.

β-Cyclodextrin based magnetic hyper-crosslinked polymer: A recyclable adsorbent for effective preconcentration of triazine herbicides in complex sample matrices

High efficiency enrichment and trace analysis of triazine herbicide residues are crucial for ensuring environmental and food safety. Herein, a series of magnetic hyper-crosslinked polymers (CD-gs-MHCPs) were synthesized with different crosslinkers, which might possess different pore structure and surface area, so they might dispay variable adsorption performance. CD-gs-MHCP2 with dichloroxylene as crosslinker delivered superior adsorption ability for triazine herbicides (THs). The synergistic effect of hydrogen bonds, hydrophobic interaction, π-π stacking interaction and pore adsorption were proved to be the main adsorption mechanism. Combined CD-gs-MHCP2 based magnetic solid-phase extraction (MSPE) with high-performance liquid chromatography, the quantitative analysis of THs in river water and vegetable samples (zucchini, pakchoi) was achieved. Under the optimal conditions, the enrichment factors for three different samples ranged from 94 to 244 and low detection limit (S/N = 3) of the four THs were obtained from 0.05 to 0.15 ng mL−1 for river water and 0.31–3.10 ng g−1 for vegetable samples. The method recoveries were in the range of 86.2 %–120 % with relative standard deviations lower than 7.4 %. This work not only offers a new strategy for fabrication β-CD-based HCPs, but also provided a practical and effective method for efficient isolation and sensitive detection of trace THs residues in complex samples.

Oyster shell facilitates the green production of nitrogen-doped porous biochar from macroalgae: a case study for removing atrazine from water

Low-cost and green preparation of efficient sorbents is critical to the removal of organic contaminants during water treatment. In this study, the co-pyrolysis of macroalgae and oyster shell was designed to synthesize nitrogen-doped porous biochars for sorption removal of atrazine from water. Oyster shell played a significant role in opening pores in macroalgae-derived biochars, resulting in the surface area of the macroalgae (Enteromorpha prolifera and Ulva lactuca) and oyster shell co-pyrolyzed carbonaceous as high as 1501.80 m2 g−1 and 1067.18 m2 g−1, the pore volume reached 1.04 cm3 g−1 and 0.93 cm3 g−1, and O/C decreased to 0.09 and 0.08, respectively. The sorption capacity of atrazine to nitrogen-doped porous biochars (the Enteromorpha prolifera, Ulva lactuca and oyster shell co-pyrolyzed carbonaceous) reached 312.06 mg g−1 and 340.52 mg g−1. Pore-filling, hydrogen bonding, π-π or p-π stacking and electrostatic interaction dominated the multilayer sorption process. Moreover, the nitrogen-doped porous biochars showed great performance in cyclic reusability, and the Enteromorpha prolifera, Ulva lactuca and oyster shell co-pyrolyzed carbonaceous sorption capacity still reached 246.13 mg g−1 and 255.97 mg g−1, respectively. Thus, this study suggested that it is feasible and efficient to remove organic contaminants with the nitrogen-doped porous biochars co-pyrolyzed from macroalgae and oyster shell, providing a potential green resource utilization of aquatic wastes for environmental remediation.Graphical

Removal of tricyclazole residues from water by sorption on metal organic frameworks (MOFs): A theoretical insight of the experimental data

All over the world, there are stringent regulations in place concerning the acceptable amount of pesticide residues in various food commodities, including cereals. The majority of the water tainted with pesticides comes from agricultural drainage, making it imperative that this water be cleansed of any lingering traces of the chemicals. The presence of unacceptable levels of pesticides residues is another issue hindering India's ability to export Basmati rice and other commodities. Tricyclazole, a fungicide has been found in rice in recent years, leading to the rejection of a number of bulk consignments. Therefore, three metal organic frameworks (MOFs) viz., MIL-53(Al), Fe-BTC, and ZIF-8, based on three different metal ions (aluminium, iron, and zinc) and three different organic "struts" were investigated for the removal of TRCZ from water. Interestingly, TRCZ was found to be selective towards both metal ions and linkers. The maximum adsorption capacities of TRCZ onto MIL-53(Al), Fe-BTC and ZIF-8 were 980.0, 896.7 and 904.6 μg g−1 (@1 ppm aqueous solution), respectively. Adsorption followed pseudo-second-order kinetics and best fit the Sips isotherm. The adsorption of TRCZ molecules onto the surface of the MOFs were confirmed using Fourier Transform infrared (FTIR) and X-Ray Diffraction (XRD) spectroscopy. MIL-53(Al) showed the best regeneration capacity (> 90 % efficiency after the 4th cycle). The adsorption of pesticide molecules onto MOF surfaces was studied (in vacuo and in aqueous) circumstances using Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) simulations revealing the prime competitive role of water molecules aided by π-π stacking and π-lone pair interactions during adsorption. Metal organic frameworks have the potential to replace costly commercial activated carbons in the future to treat pesticide-contaminated water.

The Positional Effect of an Immobilized Re Tricarbonyl Catalyst for CO2 Reduction.

The storage of renewable energy through the conversion of CO2 to CO provides a viable solution for the intermittent nature of these energy sources. The immobilization of rhenium(I) tricarbonyl molecular complexes is presented through the reductive coupling of bis(diazonium) aryl substituents. The heterogenized complex was characterized through ultra-visible, attenuated total reflectance, infrared reflection absorption spectroscopy, and X-ray photoelectron spectroscopy to probe the electronic structure of the immobilized complex. In addition, studies of cyclic voltammetry, controlled potential electrolysis, and electrochemical impedance spectroscopy were conducted to examine the CO2 reduction activity. The structure and CO2 reduction performance were compared with a previously reported immobilized rhenium(I) tricarbonyl molecular complex to probe the effect of varying the tethering of the aryl substituent from the 5,5'-position to the 4,4'-position of the 2,2'-bipyridine backbone. The immobilized complex on carbon cloth at the 4,4'-position provided excellent selectivity (FECO > 99%) and maximum TONCO and TOFCO values of 3359 and 0.9 s-1, respectively, without the addition of a Bro̷nsted acid source. A nonaqueous flow cell demonstrated the stability of this complex during a 5 h electrolysis. Tethering at the 4,4'-position, compared to the 5,5'-position, yielded lower overall activity for CO2 reduction and was attributed to the difference in growth morphology and formation of aggregations, due to Re-Re dimer formation and π-π stacking interactions within the metallopolymer matrix. For carbon cloth substrates, an optimized catalyst loading was determined to be 44.6 ± 11 nmol/cm2.

Aggregation-Induced Enhanced Electrochemiluminescence Resonance Energy Transfer Biosensor for Ultrasensitive Detection of Carcinoembryonic Antigen Based on Donor-Acceptor Organic Nanoparticles.

Aggregation-induced electrochemiluminescence (AIECL) combines the merits of aggregation-induced emission (AIE) and electrochemiluminescence (ECL), which has become a research hot spot in recent years. Therefore, we synthesized a novel AIE compound (Z)-3-(4-(2-butyl-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl)phenyl)-2-(4-(1,2,2-triphenylvinyl)phenyl)acrylonitrile (TPENI) with a donor-acceptor (D-A) structure, that is, a simple peripheral modification of 4-(2-butyl-1,3-dioxo-2,3-dihydro-1H-benzo[de]isoquinolin-6-yl) benzaldehyde (NI-CHO) with AIE-active tetraphenylethylene (TPE) to achieve the transition of NI-CHO from aggregation-caused quenching (ACQ) to an AIE molecule. When TPENI was in the aggregated state, the luminescence intensity was significantly enhanced due to the TPE structural unit restricting the free rotation of the intramolecular benzene ring, as well as the π-π stacking interactions of the molecules, which was conducive to the preparation of TPENI NPs as ECL materials. Satisfactorily, we found that the ECL intensity of TPENI NPs was increased by about 4.8-fold compared with that of the molecules dispersed in organic solution, and the stability reached about 1000 s. Based on the excellent ECL properties of TPENI NPs, an "on-off-on" ECL biosensor with a wider detection range (1 fg/mL to 100 ng/mL) and a lower detection limit of 0.20 fg/mL (S/N = 3) was proposed for sensitive analysis of a carcinoembryonic antigen (CEA). Overall, this work provided a new approach to the realization of AIECL and laid the foundation for the application of naphthalimide derivatives in ECL.

Facile synthesis of ATTM@ZIF-8 modified pullulan hydrogels for enhanced adsorption of Congo red and malachite green

Efficient capture of dyes from wastewater is of great importance for environmental remediation. Yet constructing adsorbents with satisfactory adsorption efficiency and low cost remains a major challenge. This work reports a simple and scalable method for the fabrication of functionalized porous pullulan hydrogel adsorbent decorated with ATTM@ZIF-8 for the adsorption of congo red (CR) and malachite green (MG). The embedding of ammonium tetrathiomolybdate (ATTM) into the ZIF-8 nanoclusters offered additional adsorption sites and enlarged the pore size of the resulting ATTM@ZIF-8. The homogeneous dispersion of the nanoparticles in the three-dimensional network of polysaccharide gels prevents their agglomeration and thus improves the affinity for dye molecules. The resulting adsorbent AZP-20 at optimized composite ratios exhibits high activity, selectivity, interference resistance, reusability and cytocompatibility in dye adsorption applications, and possesses high removal rate of dye in real water systems. Batch experiments demonstrated that the adsorption rate of AZP-20 for MG and CR was 1645.28 mg g−1 and 680.33 mg g−1, and would be influenced by pH conditions. Adsorption kinetics followed pseudo-second-order model. Adsorption isotherms followed Langmuir model for MG and Freundlich model for CR. The adsorption of dye molecules primarily relied on electrostatic interaction (MG) and π-π stacking interaction (CR). Conclusively, the prepared AZPs adsorbent illuminated good application prospects in the treatment of complex component dye wastewater.

Tuning the stability of DNA tetrahedra with base-stacking interactions.

DNA nanotechnology relies on programmable anchoring of regions of single-stranded DNA through base pair hybridization to create nanoscale objects such as polyhedra, tubes, sheets, and other desired shapes. Recent work from our lab measured the energetics of base-stacking interactions and suggested that terminal stacking interactions between two adjacent strands could be an additional design parameter for DNA nanotechnology. Here, we explore that idea by creating DNA tetrahedra held together with sticky ends that contain identical base pairing interactions but different terminal stacking interactions. Testing all 16 possible combinations, we found that the melting temperature of DNA tetrahedra varied by up to 10 °C from altering a single base stack in the design. These results can inform stacking design to control DNA tetrahedra stability in a substantial and predictable way. To that end, we show that a 4 bp sticky end with weak terminal stacking does not form stable tetrahedra, while strengthening the stacks confers high stability with a 46.8 ± 1.2 °C melting temperature, comparable to a 6 bp sticky end with weak stacking. The results likely apply to other types of DNA nanostructures and suggest that terminal stacking interactions play an integral role in formation and stability of DNA nanostructures.

Investigating the Effect of Chemical Modifications on the Ribose Sugar Conformation, Watson-Crick Base Pairing, and Intrastrand Stacking Interactions: A Theoretical Approach.

Over the last few decades, chemically modified sugars have been incorporated into nucleic acid-based therapeutics to improve their pharmacological potential. Chemical modification can influence the sugar conformation, Watson-Crick hydrogen (W-C) bonding, and nucleobase stacking interactions, which play major roles in the structural integrity and dynamic properties of nucleic acid duplexes. In this study, we categorized 33 uridine (U*) and cytidine (C*) sugar modifications and calculated their sugar conformational parameters. We also calculated the Watson-Crick hydrogen bond energies of the modified RNA-type base pairs (U*:A and C*:G) using DFT and sSAPT0 methods. The W-C base pairing energy calculations suggested that the South-type modified sugar strengthens the C*:G base pair and weakens the U*:A base pair compared to the unmodified one. In contrast, the North-type sugar modifications form weaker C*:G base pair and marginally stronger U*:A base pair compared to the South-type modified sugars. Moreover, intrastrand base stacking energies were calculated for 15 modifications incorporated at the fourth position in 7-mer non-self-complementary RNA duplexes [(GCAU*GAC)2 and (GCAC*GAC)2], utilizing molecular dynamics simulation and quantum mechanical (DFT and sSAPT0) methods. The sugar modifications were found to have minimal effect on the intrastrand base-stacking interactions. However, the glycol nucleic acid modification disturbs the intrastrand base-stacking significantly, corroborating the experimental data.

Utilization of the mixture of ethylene tar and different petrochemical by-products as collectors for coal flotation

ABSTRACT The ethylene tar and mixtures of ethylene tar with other petrochemical by-products were used as collectors for coal flotation. The results showed that the 1# compound collector was better than kerosene in terms of selectivity and collectibility for coal flotation. When the collector dosage was 1500 g/t, the yield of clean coal using the 1# compound collector increased by 4.05%, and the reduction in ash content was 0.36% lower compared to using kerosene. The mechanism of action of 1# compound collector on the coal surface was analyzed in combination with GC-MS tests and FTIR tests. The 1# compound collector contains more aromatics, olefins and heteropolar substances than kerosene. When the aromatics in the 1# compound collector interact with the nonpolar sites on the coal surface via π–π stacking interactions, some of the polar sites sandwiched between the aromatic compound molecules are covered. The olefins contained therein engage with the nonpolar sites on the surface experiences interactions attributable to van der Waals forces. The oxygenated functional groups of alcohols, acids, esters and carbonyl compounds engage with the polar sites on the surface of the particles through hydrogen bonding.

Hierarchical porous ACNF/MIL-68(In)–NH2 composites for rapid and efficient removal of losartan from water: Unveiling adsorption mechanisms and superior performance

Losartan (LP), a medication commonly used to treat hypertension, has emerged as a potential environmental pollutant. Despite its widespread use, research on the efficient and rapid removal of LP from the environment remains very scarce. The limited studies on LP adsorption indicate that the adsorption capacity and rate of LP need improvement. In this study, we successfully prepared a hierarchical porous nitric acid-treated carbon nanofiber (ACNF)/MIL-68(In)–NH2 composite with a robust three-dimensional support structure using a simple hydrothermal method for the first time to adsorb LP. The resulting ACNF/MIL-68(In)–NH2 composite demonstrated exceptional adsorption capabilities, achieving an equilibrium absorption capacity of 259.87 mg/g within just 64 min, significantly outperforming previously reported results. Langmuir fitting indicated a maximum theoretical adsorption capacity exceeding 630 mg/g at 55 °C. For actual wastewater with low LP concentrations, complete removal was achieved with a minimal dose of the ACNF/MIL-68(In)–NH2 adsorbent. DFT calculations and Multiwfn wavefunction analysis revealed that the adsorption behavior of LP onto ACNF/MIL-68(In)–NH2 is primarily driven by electrostatic interactions, multiple hydrogen bonds, π-π stacking interactions, and van der Waals forces. This work presents an innovative strategy for the efficient and rapid removal of residual LP from water environments.