Electrostatic Contacts Research Articles

Long range electrostatic adhesive contact between an elastic half-space and a rigid indenter with power-law profile

Abstract In this study, the electrostatic adhesive contact between smooth indenter with power-law geometry and elastic half-space is studied in both theoretical and numerical approach. Both indenter and substrate are coated with an electrically insulating layer. The Maxwell stress and hard-wall constraint are applied to describe the interaction between indenter and elastic counterface. By assuming electrostatic adhesion as a long range interaction, we derived a theoretical relation between external load and contact radius. We show that the theoretical and numerical results are plausible when the Tabor parameter is small. However, when the Tabor parameter is large, the numerical results get closer to the JKR limit. The generalized Tabor parameter, which dependent on the applied voltage and indenter shape, has been derived by following the basic idea of dimensional analysis.

Development and assessment of vanadium-based metal–organic frameworks for the effective elimination of hazardous pesticides from aqueous solutions: Mechanism of uptake, adsorption capacities, rate of uptake, and enhancement via the Box-Behnken design

Vanadium metal–organic frameworks (V-MOF) has a great potential to remove contaminants from water that come from agriculture wastewater methyl parathion (MP) pesticides with high effectiveness. Using a variety of methods, such as SEM, FT-IR, XPS), XRD, and BET analysis, the adsorbent was successfully synthesized and characterized. The dimensions of the pores measured at 1.33 nm correspond to the classification of micropores under the IUPAC system. Before the adsorption process, the material had a surface area of 1489.42 m2/g and a pore volume of 0.98 cc/g. After MP adsorption, the surface area, pore size, and pore volume decreased to 1268.42 m2/g, 1.12 nm, and 0.64 cc/g, respectively. Changes in the material’s physical properties indicate that the adsorption process had an effect. 7.2 was the result of controlling the point of zero charge through surface characterization. This information suggests that the surface of the adsorbent has a positive charge at pH below 7.2 and at the pH higher than this value the surface will have a negative charge. It was also looked into how pH affected the adsorption equilibrium. Although fitting to Langmuir isothermally, the kinetics of MP adsorption onto V-MOF are pseudo-second-order fitting. It is very probable that chemisorption was the mode of adsorption because the adsorption energy was 23.62 kJ.mol−1. The enthalpy (ΔHo) values obtained as a result of studying the thermodynamic parameters are positive, demonstrating that, within this temperature range, the pesticide adsorption process was endothermic., measuring 32.79 kJ.mol−1. Entropy (ΔSo) readings that are positive indicate that the system’s randomness increased during the adsorption process, reaching 119 J.mol−1K−1, and with rising temperatures, the negative of ΔGo rise. The effectiveness of the recommended adsorbent was evaluated by filtering wastewater samples in a laboratory environment. It is hypothesized that V-MOF and MP will interact by pore filling, π-π interaction, H-bonding, electrostatic contact, and other possible methods. Considering the specifics of this interaction in great detail is essential to comprehending the nature of adsorption and effectively constructing the adsorbent for use in real-world applications. Water filtering and the treatment of industrial effluents were made simple and effective by the use of V-MOF adsorbent technology. The results indicated that 383.6 mg/g was the maximal adsorption capacity at pH = 6. To evaluate the renewal of the adsorbent, more tests were carried out, and the outcomes showed that the renewal continued even after more than six cycles. The stability of the adsorbent during regeneration was confirmed by using XRD and FT-IR. The Box Behnken design (BBD) was then employed to optimize the adsorption outcomes.

Differential Behavior of Conformational Dynamics in Active and Inactive States of Cannabinoid Receptor 1.

Cannabinoid receptor 1 (CB1) is a G protein-coupled receptor that regulates critical physiological processes including pain, appetite, and cognition. Understanding the conformational dynamics of CB1 associated with transitions between inactive and active signaling states is imperative for developing targeted modulators. Using microsecond-level all-atom molecular dynamics simulations, we identified marked differences in the conformational ensembles of inactive and active CB1 in apo. The inactive state exhibited substantially increased structural heterogeneity and plasticity compared to the more rigidified active state in the absence of stabilizing ligands. Transmembrane helices TM3 and TM7 were identified as distinguishing factors modulating the state-dependent dynamics. TM7 displayed amplified fluctuations selectively in the inactive state simulations attributed to disruption of conserved electrostatic contacts anchoring it to surrounding helices in the active state. Additionally, we identified significant reorganizations in key salt bridge and hydrogen bond networks contributing to the CB1 activation/inactivation. For instance, D213-Y224 hydrogen bond and D184-K192 salt bridge showed marked rearrangements between the states. Collectively, these findings reveal the specialized role of TM7 in directing state-dependent CB1 dynamics through electrostatic switch mechanisms. By elucidating the intrinsic enhanced flexibility of inactive CB1, this study provides valuable insights into the conformational landscape enabling functional transitions. Our perspective advances understanding of CB1 activation mechanisms and offers opportunities for structure-based drug discovery targeting the state-specific conformational dynamics of this receptor.

Fusion Dynamics and Size-Dependence of Droplet Microstructure in ssDNA-Mediated Protein Phase Separation.

Biomolecular condensation involving proteins and nucleic acids has been recognized to play crucial roles in genome organization and transcriptional regulation. However, the biophysical mechanisms underlying the droplet fusion dynamics and microstructure evolution during the early stage of liquid-liquid phase separation (LLPS) remain elusive. In this work, we study the phase separation of linker histone H1, which is among the most abundant chromatin proteins, in the presence of single-stranded DNA (ssDNA) capable of forming a G-quadruplex by using molecular simulations and experimental characterization. We found that droplet fusion is a rather stochastic and kinetically controlled process. Productive fusion events are triggered by the formation of ssDNA-mediated electrostatic bridges within the droplet contacting zone. The droplet microstructure is size-dependent and evolves driven by maximizing the number of electrostatic contacts. We also showed that the folding of ssDNA to the G-quadruplex promotes LLPS by increasing the multivalency and strength of protein-DNA interactions. These findings provide deep mechanistic insights into the growth dynamics of biomolecular droplets and highlight the key role of kinetic control during the early stage of ssDNA-protein condensation.

Electrostatic energy-driven contact electrification mechanism from the ReaxFF molecular dynamics perspective.

Understanding the underlying principles of contact electrification is critical for more efficient triboelectric nanogenerator (TENG) development. Herein, we use ReaxFF molecular dynamics simulations in conjunction with a charge equilibration method to investigate the contact electrification mechanism in polyisoprene (PI), a natural rubber polymer, when it comes into contact with copper (Cu) and polytetrafluoroethylene (PTFE). The simulations reveal that the charge transfer directions in the PI/Cu and PI/PTFE contact models are opposite, and the amount of charge transfer in the former is substantially less than that in the latter, which are consistent with our TENG measurements. Contact electrification is revealed to be a spontaneous process that occurs to lower electrostatic energy, and the electrostatic energy released during contact electrification of PI/PTFE is greater than that of PI/Cu, which can be correlated with the relative strength of triboelectric charging observed for the two systems. A compression simulation of the PI/Cu contact model reveals that the quantity of charge transfer grows exponentially as compressive strain increases. Despite increasing the total energy of the system due to densification and distortion of the polymer structure, the applied deformation results in an energetically more stable electrostatic arrangement. We also find that the incorporation of a carbonaceous material into a polyisoprene matrix causes a faster increase in the amount of charge transfer with compressive strain, which is governed by a steeper electrostatic energy profile. This study provides an alternative perspective on the contact electrification mechanism, which could be beneficial for the development of energy harvesting devices.

Efficient adsorption of fluorescein dye from aqueous solutions by Al/Th-MOF bimetal-organic frameworks: Adsorption isotherm, kinetics, DFT computation, and optimization via Box-Behnken design

Bimetal-organic frameworks, or MOFs, have sparked a lot of interest in the wastewater treatment industry. This study investigated the possibility of removing fluorescein dye (FS) employing bimetal-organic frameworks based on aluminum and thorium (Al/Th-MOF) from aqueous solutions. To investigate the properties of the material further, scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, surface charge analysis, and X-ray diffraction (XRD) were used. Using these methods, we were able to identify the Al/Th-MOF's point of zero charge. Following adsorption, the adsorbent's large surface area of 2273.8 m2/g and pore volume of 1.4 cm3/g drop to 1678.9 m2/g and 0.96 cm3/g, individually. As this suggests, it is ideal that a portion of the FS was absorbed within the pores of the adsorbent. Through batch testing, it looked into the connection between adsorption equilibrium and pH levels, and found that changes in solution pH significantly affected adsorption behavior. Further studies with kinetic models led to the discovery of the pseudo-second-order model for FS adsorption on Al/Th-MOF. Furthermore, the Langmuir isotherm model accurately describes the adsorption process, suggesting that chemisorption played a major role in the process as a whole. To optimize factors such adsorbent dosage, time, solution pH, the response surface methodology (RSM) and Box-Behnken design (BBD) were used. As a consequence (ΔH°), (ΔS°), and (ΔG°) data the adsorption of FS employing Al/Th-MOF as an adsorbent is endothermic and spontaneous. Our study's studies have demonstrated that the Al/Th-MOF adsorbent combines a number of mechanisms, such as π-π interaction, H-bonding, pore filling, and electrostatic contact, to effectively remove FS dye from water-based solutions. The adsorption capacity of FS onto Al/Th-MOF reaches a maximum of 668.6 mg.g−1 at a pH value of 4, demonstrating that the adsorbent is particularly successful in removing FS from wastewater samples. Furthermore, the synthesized Al/Th-MOF adsorbent possesses outstanding render ability and cyclability for a maximum of eight adsorption-desorption cycles, suggesting that it could find application as an adsorbent in industrial environments. Overall, our research suggests that the adsorbent is a potential and novel approach for managing industrial effluent and water filtering.

Structural Reorganization Mechanism of the Aβ42 Fibril Mediated by N-Substituted Oligopyrrolamide ADH-353.

The inhibition of amyloid-β (Aβ) fibrillation and clearance of Aβ aggregates have emerged as a potential pharmacological strategy to alleviate Aβ aggregate-induced neurotoxicity in Alzheimer's disease (AD). Maity et al. shortlisted ADH-353 from a small library of positively charged N-substituted oligopyrrolamides for its notable ability to inhibit Aβ fibrillation, disintegrate intracellular cytotoxic Aβ oligomers, and alleviate Aβ-induced cytotoxicity in the SH-SY5Y and N2a cells. However, the molecular mechanism through which ADH-353 interacts with the Aβ42 fibrils, leading to their disruption and subsequent clearance, remains unclear. Thus, a detailed molecular mechanism underlying the disruption of neurotoxic Aβ42 fibrils (PDB ID 2NAO) by ADH-353 has been illuminated in this work using molecular dynamics simulations. Interestingly, conformational snapshots during simulation depicted the shortening and disappearance of β-strands and the emergence of a helix conformation, indicating a loss of the well-organized β-sheet-rich structure of the disease-relevant Aβ42 fibril on the incorporation of ADH-353. ADH-353 binds strongly to the Aβ42 fibril (ΔGbinding= -142.91 ± 1.61 kcal/mol) with a notable contribution from the electrostatic interactions between positively charged N-propylamine side chains of ADH-353 with the glutamic (Glu3, Glu11, and Glu22) and aspartic (Asp7 and Asp23) acid residues of the Aβ42 fibril. This aligns well with heteronuclear single quantum coherence NMR studies, which depict that the binding of ADH-353 with the Aβ peptide is driven by electrostatic and hydrophobic contacts. Furthermore, a noteworthy decrease in the binding affinity of Aβ42 fibril chains on the incorporation of ADH-353 indicates the weakening of interchain interactions leading to the disruption of the double-horseshoe conformation of the Aβ42 fibril. The illumination of key interactions responsible for the destabilization of the Aβ42 fibril by ADH-353 in this work will greatly aid in designing new chemical scaffolds with enhanced efficacy for the clearance of Aβ aggregates in AD.

Dual-enhanced enzyme cascade hybrid hydrogel for the construction of optical biosensor

The biomimetic enzyme cascade system plays a key role in biosensing as a sophisticated signal transduction and amplification strategy. However, constructing a regulated enzyme cascade sensing system remains challenging due to the mismatch of multiple enzyme activities and poor stability. Herein, we design an efficient dual-enhanced enzyme cascade hybrid system (UFD-DEC) containing DNA-controlled nanozymes (Fe-cdDNA) and enzyme (urease) via combining the electrostatic contact effect with the hydrogel-directed confinement effect. Precise modulation of Fe-cdDNA nanozyme by DNA offers a means to control its catalytic efficiency. This regulated UFD-DEC system accelerates the reaction rate and provides remarkable stability compared with the free enzyme system. Benefiting from the plasticity properties of hydrogels, a “lab-in-a-tube” platform was constructed by encapsulating UFD-DEC in a microcentrifuge tube. Such a UFD-DEC-based hydrogel tube exhibits sufficient adaptability to profile urea when used in conjunction with a smartphone-assisted image processing algorithm, which on-site delivers urea information with a detection limit of 0.12 mmol L−1. This customizable and inexpensive miniaturized biosensor platform for monitoring urea may facilitate point-of-care testing applications.

Synthesis and characterization of novel La/Rb bimetal-organic frameworks for efficient adsorption of 2,4-Dichlorophenoxyacetic acid from aqueous solutions: Adsorption isotherm, kinetics, optimization via Box-Behnken design, and DFT calculations

This work investigated the adsorption properties of lanthanum/rubidium bimetal-organic frameworks (La/Rb-MOF) with the goal of removing the hazardous herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D) from aqueous solutions. SEM, TEM, PXRD, XPS, FT-IR, and BET experiments were employed to extensively analyze the substance’s properties. A significant surface area of 1560.91 m2/g was observed in the data, suggesting a prospective for a high adsorption capability. A positive charge beyond the point of zero charge (5.14) and a negative charge after it were shown to have an impact on the adsorption behavior, according to the surface charge analysis. Through batch experiments, the study investigated how pH affected adsorption equilibrium and offered insights into the environmental variables influencing the adsorption procedure. At a pH of 4, the maximal 2,4-D adsorption onto La/Rb-MOF was found to reach 452.6 mg.g−1. The structure, reactivity and 2,4-D electrical properties were determined using density functional theory (DFT). DFT indicates that there is respectable agreement between the location of the electrophilic and nucleophilic violence sites and the molecular orbitals (HOMO and LUMO) and MEP data. The kinetics of the reaction were elucidated using pseudo-second-order kinetic models. The Langmuir isotherm model, which consistently showed a chemisorption procedure, demonstrated to be an accurate forecaster of the adsorption mechanism. Interestingly, the predicted thermodynamic characteristics of our investigation showed that the entire adsorption–desorption procedure was endothermic and spontaneous in nature (ΔH°), (ΔS°), and (ΔG°) while using the adsorbent La/Rb-MOF. La/Rb-MOF and 2,4-dichlorophenylacetic acid (2,4-D) were found to interact by a mechanism that took into account elements such as electrostatic contact, π-π interaction, and pore filling. Additional investigation evaluated the adsorbent’s capacity for regeneration while evaluating the removal efficacy and its ability to function continuously for more than eight cycles. The Box-Behnken Design was active in order to optimize the results of adsorption. This analysis highlights how La/Rb-MOF can be used to handle real-world wastewater treatment difficulties in a sustainable and practical manner.

Novel biocomposites based on carbon xerogel derived from tannin for improved cobalt (II) adsorption: practical and theoretical approaches

This study introduces a new type of biocomposite material, which is created by combining Carbon xerogel (CX) which formed from Tannin, as biopolymer, extracted from banana waste, together with several metal oxides (Fe3O4, CuO, and MgO). This biocomposite is developed to improve the adsorption of Cobalt (II) by a combination of experimental and theoretical methods. The interaction between the components of the bio composite was confirmed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) spectroscopy. Carbon xerogel/Fe3O4 composite (CX/Fe) material is arranged in a layered structure, with each layer stacked on top of the other. Furthermore, the surface roughness of the CX/Fe material after Co2+ adsorption demonstrated the improved dispersion properties of CX, as well as the weak electrostatic contact between CX and Co2+.Furthermore, thorough examinations were conducted to assess the efficacy of a bio-adsorbent in eliminating cobalt ions from wastewater across different operational circumstances. The findings indicated that carbon xerogels (CX/Fe, CX/Mg, and CX/Cu) exhibited remarkable maximum removal efficiency of around 99.66 %, 98 %, and 97.96 %, respectively, and the adsorption capacity using CX/Fe was 9.994 mg.g-1, CX/Mg was 9.9637 mg.g-1 and CX/Cu was 9.96297 mg.g-1 over a 30-min timeframe. Monte Carlo simulations showed that the examination of molecular structures involving Co2+ on CX/Fe surfaces suggests that chemical forces may have a significant influence on the adsorption process, which is consistent with the experimental findings.

Effect and mechanism of environmentally friendly depressant 2, 4-Diamino-6-hydroxypyrimidine in separation of chalcopyrite and molybdenite

It is challenging to separate between molybdenite and chalcopyrite due to their comparable hydrophobic characteristics. Inorganic depressants were previously used to separate two minerals, but the results were unsatisfactory and polluted the environment. In this study, the molybdenite and chalcopyrite were separated using a highly effective and ecologically safe depressant, 2,4-Diamino-6-hydroxypyrimidine (DAHP). According to the single mineral experiment, chalcopyrite is totally depressed while molybdenite has superior floatability. The efficacy of DAHP as the depressant was validated by further artificially mixed mineral flotation experiments, indicating the possibility of separating chalcopyrite and molybdenite. The adsorption capacity experiment results showed that the adsorption capacity of DAHP on the surface of chalcopyrite was greater than that on the surface of molybdenite. Zeta potential experiment results show that DAHP is adsorbed on the surface of chalcopyrite and molybdenite through static electrostatic interactions. X-ray photoelectron spectroscopy (XPS) experiment results show that DAHP is mainly adsorbed on chalcopyrite surface through –NH3+ group, which hinders the adsorption of kerosene. The electrostatic contact between DAHP and molybdenite has the least effect on kerosene adsorption. This study shows that DAHP has the potential to separate chalcopyrite and molybdenite as an efficient and environmentally friendly depressant.

Why Does the E1219V Mutation Expand T-Rich PAM Recognition in Cas9 from Streptococcus pyogenes?

Popular RNA-guided DNA endonuclease Cas9 from Streptococcus pyogenes (SpCas9) recognizes the canonical 5'-NGG-3' protospacer adjacent motif (PAM) and triggers double-stranded DNA cleavage activity. Mutations in SpCas9 were demonstrated to expand the PAM readability and hold promise for therapeutic and genome editing applications. However, the energetics of the PAM recognition and its relation to the atomic structure remain unknown. Using the X-ray structure (precatalytic SpCas9:sgRNA:dsDNA) as a template, we calculated the change in the PAM binding affinity in response to SpCas9 mutations using computer simulations. The E1219V mutation in SpCas9 fine-tunes the water accessibility in the PAM binding pocket and promotes new interactions in the SpCas9:noncanonical T-rich PAM, thus weakening the PAM stringency. The nucleotide-specific interaction of two arginine residues (i.e., R1333 and R1335 of SpCas9) ensured stringent 5'-NGG-3' PAM recognition. R1335A substitution (SpCas9R1335A) completely disrupts the direct interaction between SpCas9 and PAM sequences (canonical or noncanonical), accounting for the loss of editing activity. Interestingly, the double mutant (SpCas9R1335A,E1219V) boosts DNA binding affinity by favoring protein:PAM electrostatic contact in a desolvated pocket. The underlying thermodynamics explain the varied DNA cleavage activity of SpCas9 variants. A direct link between the energetics, structures, and activity is highlighted, which can aid in the rational design of improved SpCas9-based genome editing tools.

Analysing the Anticancer Properties of Pterostilbene Through Absorption, Distribution, Metabolism, and Excretion (ADME) and Molecular Docking Studies.

Aim The aim of this study is to examine the possible therapeutic effect of pterostilbene (PTS), a chemical present in grapes and blueberries, in the treatment of liver cancer by analysing its interactions with important proteins linked to the wingless/integrated (Wnt) signaling system. Objective Using computational techniques like molecular docking and absorption, distribution, metabolism, and excretion (ADME) studies, this research focuses on examining the pharmacokinetics and molecular interactions of PTS with proteins such as vimentin (Vim), glycogen synthase kinase 3 beta (GSK3-β), epithelial cadherin (E-cadherin), interleukin-6 (IL-6), interleukin-1 beta (IL-1β), c-Jun N-terminal kinase (JNK), and Wnt, all of which are connected to the Wnt signaling pathway in liver cancer. Methods The study includes the synthesis of proteins and ligands, ADME investigations for PTS, and AutoDock Vina molecular docking simulations to evaluate binding affinities and interactions. PTS is obtained from PubChem, while protein structures are obtained from the Protein Data Bank. Results Strong binding affinities between PTS and essential proteins in the Wnt signaling cascade are shown by molecular docking, which also highlights noteworthy hydrogen bonds, hydrophobic interactions, and electrostatic contacts. According to an ADME study, PTS has advantageous pharmacokinetic properties, such as moderate solubility, membrane permeability, and a minimal chance of drug interactions. Conclusion The extensive study highlights PTS's potential as a viable treatment option for liver cancer. The study promotes its investigation in cutting-edge liver cancer therapy approaches and urges more investigation into the molecular mechanisms, underpinning its anticancer properties. This paper sheds important light on the role of natural chemicals in cancer therapy and emphasizes the need for computational methods in drug discovery.

Synthesis, characterization and adsorption optimization of bimetallic La–Zn metal organic framework for removal of 2,4-dichlorophenylacetic acid

To eliminate the hazardous pesticide 2,4-dichlorophenylacetic acid (2,4-D) through aqueous solutions, stacked nanorods known as hetero bimetallic organic frameworks (MOFs) of 2-methyl imidazole based on lanthanum and zinc are created. The research's convincing discoveries displayed that La/Zn-MOF is an actual adsorbent for the removal of 2,4-D through aqueous solutions. The La/Zn-MOF was investigated using a variability of techniques, with scanning electron microscope (SEM), powered X-ray diffraction (PXRD), and Brunauer-Emmett-Teller (BET) investigation. La/Zn-MOF has a significant pore capacity of 1.04 cm³/g and a comparatively large surface area of 897.69 m2/g. Our findings, which are quite intriguing, demonstrate that adsorption behavior is pointedly wedged by variations in pH. A pH 6 dose of 0.02 g was shown to be the optimal setting for the greatest capacity for adsorption. Because adsorption is an endothermic process, temperature variations affect its capability. The adsorption method was fit both isothermally and kinetically using the Langmuir isotherm classical. It was created that the entire process made use of a chemisorption mechanism. Solution pH, temperature, adsorbent dosage, and time were all improved using the Box-Behnken design (BBD) and Response Surface Methodology (RSM). We were able to accurately calculate the values of ΔHo, ΔSo, and ΔGo for 2,4-D by following the guidelines. These results demonstrated the spontaneous and endothermic character of the adsorption procedure employing La/Zn-MOF as an adsorbent. Adsorption-desorption cycles can be carried out up to five times. With the synthesized La/Zn-MOF adsorbent due to its exceptional reusability. Many processes, such π-π interaction, pore filling, H-bonding, or electrostatic contact, were postulated to explain the connection between La/Zn-MOF and 2,4-D after extra research to appreciate well the link was conducted. This is the first study to demonstrate the effectiveness of utilizing La/Zn-MOF as an adsorbent to eliminate 2,4-D from wastewater models. The results display that a pH of 6 is required to achieve the maximal 2,4-D adsorption capability on La/Zn-MOF, which is 307.5 mg/g.

Experimental demonstration of the electrostatic induction and contact electrification for the ventilator-like of rotary nanogeneration

A fluorinated ethylene propylene (FEP) ring tube embedded in the bottom of ventilator to harvest additionally mechanical energy is introduced for hybrid inductive/triboelectric nanogenerator (H-TENG). First, charging glass bead moving closed to acrylic plane has distinctly identified for inductive polarities. Relationships between the moving speed on bead, charging bead amount and bead material with acrylic thickness have been thoroughly investigated. Results reveal that not only high moving speed but also bead charging and thin thickness enhance power output which possesses potential application for energy generation and self-powered sensor. Based on these results, the optimal H-TENG device combined with appropriate number of glass beads which conjuncts with three sets of electric brushes and heigh rotating speed enable to light up 121 LED lights. This study presents the inductive/triboelectricity mechanism of H-TENG by solid-dielectric base of rotating structure and inspires many imaginations of for harvesting large scale energy in the future.

Synthesis and characterization of metal–organic frameworks based on thorium for the effective removal of 2,4-dichlorophenylacetic pesticide from water: Batch adsorption and Box-Behnken Design optimization, and evaluation of reusability

This study aimed to assess the effectiveness of thorium metal–organic frameworks (Th-MOF) as an adsorbent for the removal of the hazardous herbicide 2,4-dichlorophenylacetic (2,4-D) from aqueous solutions. The experimental results convincingly demonstrate Th-MOF's capability as an adsorbent, effectively eliminating 2,4-D from water. The material's properties were thoroughly examined using SEM, TEM, PXRD, XPS, FT-IR, and BET studies, revealing a substantial surface area of 1122.12 m2/g, indicative of its potential for high adsorption capacity. Surface charge analysis indicated a positive charge below the point of zero charge (5.2) and a negative charge above it, influencing the adsorption behavior. The study explored the impact of pH on adsorption equilibrium through batch experiments, providing insights into the environmental factors affecting the adsorption process. In summary, this research highlights Th-MOF as a promising adsorbent for 2,4-D removal, contributing valuable insights into its characteristics and performance in water treatment applications. The significance of our findings lies in the clear impact of variations in solution pH on the adsorption behavior observed in the study. We conducted a detailed investigation into the effectiveness of 2,4-dichlorophenylacetic acid (2,4-D) adsorption on Th-MOF, employing pseudo-second-order kinetic models to unravel the kinetics of the process. The Langmuir isotherm model proved to be a reliable predictor of the adsorption mechanism, highlighting a chemisorption process throughout. Intriguingly, our study revealed that the entire adsorption–desorption process was characterized by an endothermic and spontaneous nature, as indicated by the calculated thermodynamic parameters (ΔH°), (ΔS°), and (ΔG°) when utilizing Th-MOF as the adsorbent. Furthermore, the artificially synthesized Th-MOF adsorbent showcased exceptional flexibility and cyclability, successfully undergoing up to six adsorption–desorption cycles. This versatility underscores the potential practical applications of Th-MOF in water treatment processes, emphasizing its effectiveness and recyclability for sustainable environmental remediation efforts. In a scaled-down laboratory demonstration of wastewater treatment, we evaluated the efficacy of the developed adsorbent. The interaction mechanism between Th-MOF and 2,4-dichlorophenylacetic acid (2,4-D) was closely examined, considering factors like H-bonding, π-π interaction, pore filling, or electrostatic contact. The Th-MOF adsorbent demonstrated its capability for efficient water filtration and industrial wastewater management. Our study is noteworthy for pioneering the method for removing 2,4-D from wastewater samples using the Th-MOF adsorbent. Results revealed maximum 2,4-D adsorption onto Th-MOF at a pH of 4, reaching 358.3 mg.g − 1. Further exploration assessed removal efficacy from real samples and the sustained performance of the adsorbent through more than six cycles, with attention to its regeneration potential. The optimization of adsorption outcomes was achieved through the utilization of the Box-Behnken Design. This analysis underscores the practical application and sustainability of Th-MOF in addressing real-world wastewater treatment challenges.

Mechanism for Electrostatically Generated Magnetoresistance in Chiral Systems without Spin-Dependent Transport.

Significant attention has been drawn to electronic transport in chiral materials coupled to ferromagnets in the chirality-induced spin selectivity (CISS) effect. A large magnetoresistance (MR) is usually observed, which is widely interpreted to originate from spin (dependent) transport. However, there are severe discrepancies between the experimental results and the theoretical interpretations, most notably the apparent failure of the Onsager reciprocity relations in the linear response regime. We provide an alternative mechanism for the two terminal MR in chiral systems coupled to a ferromagnet. For this, we point out that it was observed experimentally that the electrostatic contact potential of chiral materials on a ferromagnet depends on the magnetization direction and chirality. The mechanism that we provide causes the transport barrier to be modified by the magnetization direction, already in equilibrium, in the absence of a bias current. This strongly alters the charge transport through and over the barrier, not requiring spin transport. This provides a mechanism that allows the linear response resistance to be sensitive to the magnetization direction and also explains the failure of the Onsager reciprocity relations. We propose experimental configurations to confirm our alternative mechanism for MR.

The Impact of Lens Epithelium-Derived Growth Factor p75 Dimerization on Its Tethering Function.

The transcriptional co-activator lens epithelium-derived growth factor/p75 (LEDGF/p75) plays an important role in the biology of the cell and in several human diseases, including MLL-rearranged acute leukemia, autoimmunity, and HIV-1 infection. In both health and disease, LEDGF/p75 functions as a chromatin tether that interacts with proteins such as MLL1 and HIV-1 integrase via its integrase-binding domain (IBD) and with chromatin through its N-terminal PWWP domain. Recently, dimerization of LEDGF/p75 was shown, mediated by a network of electrostatic contacts between amino acids from the IBD and the C-terminal α6-helix. Here, we investigated the functional impact of LEDGF/p75 variants on the dimerization using biochemical and cellular interaction assays. The data demonstrate that the C-terminal α6-helix folds back in cis on the IBD of monomeric LEDGF/p75. We discovered that the presence of DNA stimulates LEDGF/p75 dimerization. LEDGF/p75 dimerization enhances binding to MLL1 but not to HIV-1 integrase, a finding that was observed in vitro and validated in cell culture. Whereas HIV-1 replication was not dependent on LEDGF/p75 dimerization, colony formation of MLLr-dependent human leukemic THP-1 cells was. In conclusion, our data indicate that intricate changes in the quaternary structure of LEDGF/p75 modulate its tethering function.

Modelling and optimization of Victoria blue uptake using response surface methodology (RSM) with novel magnetic folic acid-mannitol/mosquito coil ash nanocomposite

Recently, natural, and environmentally safe polymer-metal oxide hybrid nanocomposites have been increasingly noticed as cost-effective adsorbents for pollutant removal. In this context, a novel hybrid nanocomposite was prepared from a FAM copolymer synthesized by thermal poly-esterification and FAM-MCA/Fe3O4 obtained by the simple in-situ co-precipitation method. Following its structure elucidation using XRD, the nanomaterials were further characterized by FTIR and their surface analysis by using SEM-EDX, TEM and BET methods. The physicochemical characterization of the nanohybrid was accomplished and its performance and effectiveness in removing VB dye from simulated effluents was evaluated. The reaction surface method was used to optimize the operating conditions in terms of contact time (59.9 min), initial concentration VB (60 mg/L), dose of nanocomposite (0.15 g/L), and initial solution pH (6.0). The equilibrium results modelled with nonlinear isothermal and kinetic models complied well with the Langmuir isotherm and pseudo-second-order kinetics with both intraparticle and film diffusion driving the adsorption process. The enhanced adsorption performance of the NC was demonstrated by the significantly higher Langmuir saturation capacity (FAM-MCA/Fe3O4: 279; Fe3O4: 244 mg VB /g) at 303 K compared to other previously reported adsorbents and the strong recyclability while maintaining the adsorption effectiveness of 61.46 % up to five consecutive cycles. Using the deduced thermodynamic parameters, an exothermic, spontaneous, and practicable VB elimination process was established. The adsorption process was principally controlled by electrostatic contact, Yoshida H-bonds, dipole-dipole, n-π stacking, cation-π and, π-π interactions. A complete cost study was performed to assess the economic viability of the adsorbents. FAM-MCA/Fe3O4 was discovered to be the most affordable (551 INR/kg) approach for VB removal. The investigative findings unveiled that the as synthesized hybrid nanocomposite was a potent adsorbent for effective and efficient liquid-phase amputation of VB.

Flanking AT base pairs affect the localization of monovalent cations in DNA A-tracts.

Capillary electrophoresis has been used to measure the free solution mobilities of a series of 26-base pair (bp) DNA oligomers containing two phased A4T1in-tracts embedded in flanking sequences containing 0 to 11 additional AT bps. A random-sequence 26-bp oligomer with 12 isolated AT bps was used as the reference. Mobility ratios (A-tract/reference) were measured in background electrolytes (BGEs) containing mixtures of small monovalent cations and tetrabutylammonium (TBA+ ) or tetrapropylammonium (TPA+ ) ions. The mobility ratios observed in 0.3M TBA+ were >1.00, suggesting that the TBA+ ions had formed electrostatic contact pairs with the AT bp in the reference and in the A-tract flanking sequences, decreasing the mobilities of both oligomers. The TBA-AT pairing interactions could be eliminated by increasing the concentration of small monovalent cations in the BGE. In 0.3M TPA+ , electrostatic contact pairs were formed with the AT bps in the flanking sequences and in the A-tracts. Interestingly, the shapes of the mobility ratio profiles observed for the A4T1in-tract oligomers depended on the total number of A+T residues in the oligomer.