DFT study of the mechanism of the reaction of aminoguanidine with methylglyoxal

Density functional theory calculations were used in the theoretical investigation of the adsorption properties of sumanene towards molecules considered as common air pollutants: CO, CO₂ and NH₃. The insignificant perturbation of sumanene after adsorption and the adsorption energies obtained indicate a physisorption mechanism. It was shown that, contrary to carbon nanotubes, sumanene is able to adsorb CO molecules, and that adsorption of CO₂ by sumanene is stronger than adsorption of CO₂ by C₆₀. To better understand the adsorption characteristics of sumanene, density of states and natural bond order analyses were performed, which showed that chemical interactions exist and that these are more important mostly on the convex side. Better adsorption properties were obtained for the concave side as adsorption is dictated by physisorption mechanisms due to the specific bowl-shaped geometry of sumanene, because of which more negative charge is located precisely on the concave side. Molecular electrostatic potential surfaces were also used in order to better locate the adsorption sites and gain additional details about adsorption.

The adsorption of NO,NH<Subscript>3</Subscript>, N<Subscript>2</Subscript> on carbon surface: a density functional theory study

To explore the adsorption mechanism of NO, NH₃, N₂ on a carbon surface, and the effect of basic and acidic functional groups, density functional theory was employed to investigate the interactions between these molecules and carbon surfaces. Molecular electrostatic potential, Mulliken population analyses, reduced density gradient, and Mayer bond order analyses were used to clarify the adsorption mechanism. The results indicate that van der Waals interactions are responsible for N₂ physisorption, and N₂ is the least likely to adsorb on a carbon surface. Modification of carbon materials to decorate basic or acidic functional groups could enhance the NH₃ physisorption because of hydrogen bonding or electrostatic interactions, however, NO physisorption on a carbon surface is poor. Zig-zag sites are more reactive than armchair sites when these gas molecules absorb on the edge sites of carbon surface.

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Graphical abstract NH₃, N₂, NO adsortion on carbon surface

     

Prediction of chlortetracycline adsorption on the Fe3O4 nanoparticle using molecular dynamics simulation

Abstract

Molecular dynamics (MD) simulation was applied to investigate the adsorption mechanism of chlortetracycline (CTC) antibiotic molecule as the aqueous pollutant on the Fe₃O₄ nanoparticle (NP). Two different NP sizes with a diameter of about 1.4?nm and 3.5?nm were selected. Initially, the stability of both NPs in water was investigated by calculating radial distribution function curves of NP atoms. Simulation results confirmed the stable crystallographic structures of both NPs. However, small NP induce greater structural stabilization. Then, CTC molecules were adsorbed on NPs surface in various pollutant concentrations. Electrostatic and hydrogen bond were the major types of interactions between CTC molecules and the adsorbent surface. CTC molecules formed a complex with NP surface from their amine side chains; while they were parallel to each other in their aromatic rings and π-π bond between two CTC molecules was formed. Diffusion rate of CTC molecules could predict the adsorption mechanism. At lower concentration of CTC, CTC molecules tend to adsorb on the NP surface. At these concentrations, the diffusion rate of CTC was high. By increasing the CTC concentration, the pollutant agglomeration was enhanced which decreased the diffusion rate. At this time, the surface of NP was saturated. In addition, the results of isotherm curves showed that CTC adsorption on small NPs could be defined with both Langmuir and Freundlich isotherm models, while Freundlich isotherm model was more appropriate for larger NPs. In conclusion, observations confirmed that MD simulation could successfully predict the behavior of CTC adsorption on the Fe₃O₄ NP surface.

Communicated by Ramaswamy H. Sarma     

Prediction of electrocatalytic activity of some nitrogen-doped polyaromatic hydrocarbons by molecular modelling

Density function theory calculations of minimum energy structure of an oxygen molecule and oxygen atom bonded to the two dimensional molecules, C₂₃NH₁₂, coronene and C₂₁NH₁₄, pentacene doped with nitrogen, indicate the structures are at a minimum on the potential energy surface having no imaginary frequencies. Calculation of the bond dissociation energy (BDE) to remove an oxygen atom from nitrogen-doped pentacene to which is bonded O₂, (C₂₁NH₁₄O₂) shows it is less than that to dissociate O₂. However, this is not the case for nitrogen-doped coronene. This suggests that nitrogen-doped pentacene could be an effective catalyst for the oxygen reduction reaction in fuel cells assuming it is O₂ dissociation. It is also shown that O₂H can bond to nitrogen-doped coronene and pentacene and that the BDE to remove OH is less than that to remove OH from O₂H indicating that N-doped coronene and pentacene could also catalyse this reaction. The calculated adsorption energy for O₂ and O₂H on these molecules is negative indicating they can bond to N-doped coronene and pentacene.     

Ammonium adsorption on Brønsted acidic centers on low-index vanadium pentoxide surfaces

Vanadium-based catalysts are used in many technological processes, among which the removal of nitrogen oxides (NO_x) from waste gases is one of the most important. The chemical reaction responsible for this selective catalytic reaction (SCR) is based on the reduction of NO_x molecules to N₂, and a possible reductant in this case is pre-adsorbed NH₃. In this paper, NH₃ adsorption on Brønsted OH acid centers on low-index surfaces of V₂O₅ (010, 100, 001) is studied using a theoretical DFT method with a gradient-corrected functional (RPBE) in the embedded cluster approximation model. The results of the calculations show that ammonia molecules are spontaneously stabilized on all low-index surfaces of the investigated catalyst, with adsorption energies ranging from ?0.34 to ?2 eV. Two different mechanisms of ammonia adsorption occur: the predominant mechanism involves the transfer of a proton from a surface OH group and the stabilization of ammonia as an NH₄ ⁺ cation bonded to surface O atom(s), while an alternative mechanism involves the hydrogen bonding of NH₃ to a surface OH moiety. The latter binding mode is present only in cases of stabilization over a doubly coordinated O(2) center at a (100) surface. The results of the calculations indicate that a nondirectional local electrostatic interaction with ammonia approaching a surface predetermines the mode of stabilization, whereas hydrogen-bonding interactions are the main force stabilizing the adsorbed ammonia. Utilizing the geometric features of the hydrogen bonds, the overall strength of these interactions was quantified and qualitatively correlated (R?=?0.93) with the magnitude of the stabilization effect (i.e., the adsorption energy).

Computational study of the NO,SO<Subscript>2</Subscript>, and NH<Subscript>3</Subscript> adsorptions on fragments of 3N-graphene and Al/3N graphene

The adsorption properties of common gas molecules (NO, NH₃, and SO₂) on the surface of 3N-graphene and Al/3N graphene fragments are investigated using density functional theory. The adsorption energies have been calculated for the most stable configurations of the molecules on the surface of 3N-graphene and Al/3N graphene fragments. The adsorption energies of Al/3N graphene-gas systems are ?220.5 kJ mol^?1 for Al/3NG-NO, ?111.9 kJ mol^?1 for Al/3NG-NH₃, and ?347.7 kJ mol^?1 for Al/3NG-SO₂, respectively. Compared with the 3N-graphene fragment, the Al/3N graphene fragment has significant adsorption energy. Furthermore, the molecular orbital, density of states, and electron densities distribution were used to explore the interaction between these molecules and the surface. We found that orbital hybridization exists between these molecules and the Al/3N graphene surface, which indicates that doping Al significantly increases the interaction between the gas molecules and Al/3N graphene. In addition, compared with Li, Al can more powerfully enhance adsorption of the 3N-graphene fragment. The results indicate that Al/3N graphene can be viewed as a new nanomaterial adsorbent for NO, NH₃, and SO₂.     

Oxidative degradation of quinazoline in supercritical water: a combined ReaxFF and DFT study

ABSTRACT

Quinazoline (Qu) is a representative heterocyclic compound in chemical wastewater. In this work, the supercritical water oxidation of Qu is investigated using molecular dynamics simulations based on the ReaxFF reactive force field combined with density functional theory (DFT) method. The detailed reaction pathways, transformation routes of nitrogen element, and kinetic behaviours are systematically analyzed at the atomistic level. Simulation results show that the increment of temperature and O₂ molecule accelerates the reaction rate and facilitates the complete destruction of Qu. The pyrimidine ring in Qu can be attacked by the OH radical, O₂ molecule, and H₂O molecule, thereby causing three main pathways for the pyrimidine ring-opening reaction. The aromatic ring undergoes a ring rearrangement process and opens under the attack of active O₂ molecules. DFT calculations demonstrate that the supercritical water cluster can decrease the cracking energy of chemical bonds and accelerate the degradation rate of Qu. In addition, the transformation routes of nitrogen element during reaction are described. NH₃ is found to be the primary N-containing product after ring-opening reactions and is an intermediate for the production of N₂. Finally, the value of activation energy is obtained as 123.0?kJ/mol, which is reasonably consistent with the experimental results.     

A simple aqueous phase synthesis of high surface area aluminum fluoride and its bulk and surface structure

A simple novel synthesis route to aluminum fluoride, AlF₃, from aqueous phase is reported. Al₂O₃ is dissolved in aqueous hydrofluoric acid, HF, and re-precipitated as AlF₃ · 3H₂O. Thermal decomposition results in thermally stable AlF₃ with high specific surface areas between 120 and 60 m²/g depending on treatment temperatures (up to 450 °C). Bulk and surface structures of the resulting amorphous and crystalline materials were characterized by X-ray powder diffraction, infrared and solid state NMR spectroscopy (²⁷Al, MAS), nitrogen physisorption and adsorption of paramagnetic probe molecules (vanadium complexes).     

Theoretical Study of the TiO2 and MgO Surface Acidity and the Adsorption of Acids and Bases

We present ab-initio periodic Hartree–Fock calculations (crystal program) of small molecules on TiO₂ and MgO. The adsorption of the molecules may be molecular or dissociative. This depends on their acid and basic properties in the gas phase. For the molecular adsorption, the molecules are adsorbed as bases on Ti(+IV) sites, the adsorption energies correlate with the proton affinities. The dissociations on the surface correlate with the gas phase cleavages: thus, the dissociation of MeOH leads to a preferential basic cleavage (the fragment HO– is adsorbed on a Ti⁺⁴ ion and the fragment Me⁺ is adsorbed on a O²– ion of the oxide). The opposite result is obtained with MeSH. Another important factor is the adsorbate–adsorbate interaction: favorable cases are a sequence of H-bonds for the hydroxyl groups resulting from the water dissociation and the mode of adsorption for the ammonium ions. Lateral interactions also force the adsorbed CO₂ molecules to bend over the surface so that their mutual orientation resembles the geometry of the CO₂ dimer. With respect to water adsorption, MgO appears to be a basic oxide. As experimentally observed, NH₃ adsorbs preferentially on TiO₂ and CO₂ on MgO. However, this difference of reactivity should not be expressed in terms of acid vs. basic behaviour but in terms of hard and soft acidity. The MgO surface is a 'soft' acidic surface that reacts preferentially with the soft base, CO₂.     

Effect of thiol-functionalised silica on cisplatin adsorption

This study contributes to the investigation related to guest–host interactions between the chemotherapeutic agent cisplatin and a functionalised silica matrix in order to improve and find new materials such as drug carriers. The adsorption of cisplatin and its complexes, cis-[PtCl(NH₃)₂]⁺ and cis-[Pt(NH₃)₂]²⁺, on a SH-functionalised SiO₂(111) surface has been studied by the atom superposition and electron delocalisation method. The adiabatic energy curves for the adsorption of the drug and its products on the delivery system were considered. The electronic structure and bonding analysis were also performed. The molecule and their complex are adsorbed on the functionalised surface resulting in a major absorption of the cis-[Pt(NH₃)₂]²⁺ complex. The molecule–surface interactions are formed via –SH group. The molecule/complexes SH electron-donating effect plays an important role in the catalytic reaction. The more important drug–carrier interactions occur through the Cl–H bond for the adsorption of cis-[PtCl₂(NH₃)₂] and cis-[PtCl(NH₃)₂]⁺, and through the Pt–S and Pt–H interactions for cis-[Pt(NH₃)₂]²⁺ adsorption. When the new interactions are formed, the functionalised carrier maintains their matrix properties while the molecule is the most affected after adsorption. The Pt atomic orbitals present the most important changes during adsorption.     

Arsenic trioxide induces apoptosis through JNK and ERK in human mesothelioma cells

Malignant mesothelioma is an aggressive tumor of serosal surfaces, which is refractory to current treatment options. Arsenic trioxide (As₂O₃) is used clinically to treat acute promyelocytic leukemia, and also to inhibit proliferation of several solid tumors including hepatoma, esophageal, and gastric cancer in vitro. Here we found that As₂O₃ inhibited cell viability of a mesothelioma cell line, NCI‐H2052. As₂O₃ induced apoptosis of NCI‐H2052 cells, which was accompanied by activation of c‐Jun NH₂‐terminal kinase (JNK)1/2, extracellular signal‐regulated kinase (ERK)1/2, and caspase‐3. zVAD‐fmk, a broad‐spectrum caspase inhibitor, inhibited As₂O₃‐induced apoptosis and activation of caspase‐3, but not that of JNK1/2 and ERK1/2. Small interfering RNAs (siRNAs) targeting JNK1/2 suppressed As₂O₃‐induced caspase‐3 activation and apoptosis, indicating that JNK1/2 regulate As₂O₃‐induced apoptosis though caspase cascade. Furthermore, JNK1 siRNA abrogated As₂O₃‐induced JNK2 phosphorylation and JNK2 siRNA abrogated As₂O₃‐induced JNK1 phosphorylation, suggesting that JNK1 and JNK2 interact with each other. Moreover, JNK1 siRNA, but not JNK2 siRNA, abrogated As₂O₃‐induced ERK1/2 phosphorylation. JNK2 siRNA together with PD98059, a specific MAPK/ERK kinase inhibitor, suppressed As₂O₃‐induced apoptosis more significantly than JNK2 siRNA alone. These results indicated that As₂O₃ induces apoptosis of NCI‐H2052 cells mainly through JNK1/2 activation, and that ERK1/2 is involved in As₂O₃‐induced apoptosis when JNK1/2 are inactivated. J. Cell. Physiol. 226: 762–768, 2011. © 2010 Wiley‐Liss, Inc.     

Accurate acid dissociation constant (pKa) calculation for the sulfachloropyridazine and similar molecules

In this work, the interaction of GaN nanotube (GaNNT) with common air pollutants of industrialized cities, such as NH₃, NO₂ and SO₂ in different configurations was studied. For this study, the single-walled (10,0) GaNNT was used. The analysis was done via the density functional theory implemented in the SIESTA simulation software. The analysis of the results shows that the air pollutants alter the properties of nanotubes when they interact with them. The stability analysis shows that the most stable configurations are those in which adsorption occurs through a chemical process. The systems remain semiconductors, but in the case of NO₂ and SO₂ molecules interacting with GaNNT, there was a significant reduction in the energy gap. Our results also indicate that GaNNT is a promising material to detect and remove NH₃ and NO₂ molecules from the environment; however, it may be not applicable to detect or remove SO₂, because the latter interacts strongly with the nanotube, which prevents the GaNNT from being reused.

     

Effect of lycopene on As2O3 induced oxidative stress in SH-SY5Y cells

It is known that oxidative stress may cause neuronal injury and several experimental models showed that As₂O₃ exposure causes oxidative stress. Lycopene, a carotenoid, has been shown to have protective effect in neurological disease models due to antioxidant activity, but its effect on As₂O₃-induced neurotoxicity is not identified yet. The aim of this study is to investigate the effects of lycopene on As₂O₃-induced neuronal damage and the related mechanisms. Cell viability was determined by the MTT assay. Lycopene was administrated with different concentrations (2, 4, 6 and 8 µM) one hour before 2 µM As₂O₃ exposure in SH-SY5Y human neuroblastoma cells. The anti-oxidant effect of lycopene was determined by measuring superoxide dismutase (SOD), catalase (CAT) hydrogen peroxide (H₂O₂), malondialdehyde (MDA), total antioxidant status (TAS) and total oxidant status (TOS). MTT results and LDH cytotoxicity analyses showed that pretreatment with 8 µM lycopene significantly improved the toxicity due to As₂O₃ exposure in SH?SY5Y neuroblastoma cells. Pretreatment with lycopene significantly increased the activities of anti?oxidative enzymes as well as total antioxidant status and decreased total oxidative status in As₂O₃ exposed cells. The results of this study indicate that lycopene may be a potent neuroprotective against oxidative stress and could be used to prevent neuronal injury or death in several neurological diseases.

     

Influence of NH3/CO2 Modification on the Characteristic of Biochar and the CO2 Capture

This paper was aimed to study the influence of modification of biochar on the performance of CO₂ adsorption. Biochar, obtained from cotton stalk pyrolysis in a fixed bed reactor, was modified with ammonia and CO₂. The physicochemical properties of biochars were characterized by the Fourier transform infrared spectroscopy and automatic adsorption equipment (Micromeritics, ASAP 2020, USA). CO₂ adsorption of biochar was performed in thermogravimetric analyzer. The results showed that the surface area of char was increased significantly by CO₂ modification, while N-contained compound on char surface was enriched obviously by NH₃ modification. CO₂ adsorption of biochar increased greatly with CO₂ and NH₃ modification. CO₂ adsorption was mainly attributed to physical adsorption at 20 °C, and the adsorption quantity (maximum = 99 mg/g) was proportional to the micropore volume of the char. However, at 120 °C, molecular thermal motion increase, chemical adsorption start to play a dominated role, and the adsorption was directly proportional to the N content of this char.     

Attenuation of arsenic trioxide induced cardiotoxicity through flaxseed oil in experimental rats

Objectives: Arsenic trioxide (As₂O₃) is a potent drug for acute promyelocytic leukaemia, but its clinical trials are allied with some serious adverse events mainly cardiac functional abnormalities. So the objective of our investigation is to identify the cardioprotective action of flaxseed oil (FSO), a natural compound against As₂O₃ induced cardiotoxicity.

Methods: Male wistar rats were treated with As₂O₃ (4?mg/kg) to induce cardiotoxicity. FSO (250 and 500?mg/kg) was given in combination with As₂O₃ for evaluating its cardioprotective efficacy.

Results: Treatment with As₂O₃ resulted in deposition of arsenic in heart tissue, increased cardiac marker enzymes release, lipid peroxidation (LPO), oxidative insults and pathological damages in the heart. Co-treatment with FSO (500?mg/kg) significantly reduced the arsenic accumulation, cardiac marker enzymes, LPO and cardiac structural alterations. FSO treatment significantly improved cardiac glutathione content, antioxidant enzymes and reduced the pathological damages in cardiac tissue. Gas chromatographic–mass spectrometry analysis revealed that the major fatty acid content in the FSO is alpha-linolenic acid, which has a strong milieu in cardiac health.

Conclusion: The results of the current investigation suggested that FSO is an effective agent in reducing arsenic-induced cardiac toxicity and can be used as an adjunct/dietary supplement for the cancer patients on As₂O₃ therapy.     

Immobilization of penicillin G acylase on paramagnetic aldehyde-functionalized mesostructured cellular foams

Paramagnetic aldehyde-functionalized mesostructured cellular foams (PAMCFs), synthesized by grafting 3-aminopropyltriethoxysilane modified Fe₃O₄ (NH₂-Fe₃O₄) nanoparticles with larger particle size than the window pore size of MCFs on the outer surface of aldehyde-functionalized mesostructured cellular foams (AMCFs), were investigated as efficient supports for immobilization of penicillin G acylase (PGA). The results show that NH₂-Fe₃O₄ nanoparticles were successfully grafted on the outer surface of AMCFs and PGA molecules were mainly immobilized covalently on the inner surface of PAMCFs, which was because amino groups of NH₂-Fe₃O₄ nanoparticles or PGA molecules reacted with aldehyde groups of AMCFs or PAMCFs to form imine bonds. PGA/PAMCFs-15 showed a rather high initial activity of 9563 U g⁻¹ and retained 89.1% of its initial activity after recycled for 10 times. PGA/PAMCFs are easily recycled by magnetic field in order to replace tedious separation of high-speed centrifugation for mesoporous materials.     

Arsenic trioxide inhibits the growth of Adriamycin resistant osteosarcoma cells through inducing apoptosis

Given that arsenic trioxide (As₂O₃) has been successfully used as a chemotherapeutic agent for refractory malignant tumors, this study is aimed at investigating the effect of As₂O₃ on human Adriamycin resistant osteosarcoma cell line Saos-2. The mechanism underlying multi drug resistance (MDR) in osteosarcoma cells and the anti-tumor effect of As₂O₃ on Adriamycin resistant osteosarcoma cells were analyzed. In our experiment, we first selected Adriamycin resistant osteosarcoma cell line by growing the classic osteosarcoma cell line Saos-2 in the medium with increasing drug concentrations. Then, we compared the IC50s of the osteosarcoma cells treated with different anticancer drugs by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Subsequently, we assessed the expression of classic MDR related molecules, Pgp, multidrug resistance-associated protein (MRP) and glutathione (GSH) activity in the wild type and Adriamycin resistant Saos-2 cells. Furthermore, the apoptosis was assessed by concerning DNA fragment and flow cytometry with Annexin-V staining. To elucidate the underlying mechanism of the apoptosis, related proteins Bcl-2, Bcl-xL, Bax, Bak, cleaved Caspase-3 and cleaved Caspase-9 were analyzed by western blotting. The data showed that the resistance to Adriamycin affected the sensitivity of osteosarcoma cell to other chemotherapeutic agents. The IC50s of Saos-2/ADM cells for methotrexate (1.74-fold), Cisplatin (1.43-fold) and As₂O₃ (1.21-fold) were increased compared with Saos-2 control cells. The expression of Pgp was upregulated comparing with the control cells. No significant difference was detected about the MRP and the glutathione-S-transferase activity and intracellular GSH concentration among different treated osteosarcoma cells. Apoptosis was observed and proved. The western blotting showed that the expression of Bcl-2 and Bcl-xL was downregulated. Meanwhile, the level of Bax, Bak, cleaved Caspase-3 and cleaved Caspase-9 was upregulated after treated with As₂O₃. The study suggests that Adriamycin resistant osteosarcoma cells have good response to As₂O₃-based chemotherapy in vitro, probably via the pathway of inducing apoptosis. And As₂O₃ might serve as an excellent alternative candidate for adjuvant chemotherapeutic agent on this incurable pediatric sarcoma.     

Arsenic Trioxide Co-exposure Potentiates Benzo(a)pyrene Genotoxicity by Enhancing the Oxidative Stress in Human Lung Adenocarcinoma Cell

Although both arsenic trioxide (As₂O₃) and benzo(a)pyrene (BaP) are well-established human carcinogens, the interaction between As₂O₃ and BaP is synergistic or antagonistic remains controversial in terms of the existing studies. In addition, the mechanisms responsible for the combined effects are still unclear. In this study, we examined the potential interactive effects between As₂O₃ (1, 5, and 10 μM) and BaP (5, 10, and 20 μM) in cultured A549 cells by treating with BaP and As₂O₃ alone or in combination at various concentrations for 24 h. The single and combined effects of As₂O₃ and BaP on the cytotoxicity, DNA/chromosomal damage, and oxidative stress were examined by using tetrazolium (3-(4,5-dimethyithiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) dye colorimetric assay, colony formation assay, fluorescence probe, chemical colorimetry, comet assay as well as micronucleus test. Our results showed that As₂O₃ synergistically enhanced the cytotoxicity, genotoxicity, and level of oxidative stress induced by BaP at various tested concentrations. Also, our experimental results showed that intracellular glutathione (GSH) contents were increased by various doses of BaP, but single or cotreatment with As₂O₃ significantly decreased the GSH level in the cells at all tested concentrations. Taken together, our results suggest that As₂O₃ may exert its synergistic cyto- and genotoxic effects with BaP mainly via elevated intracellular reactive oxygen species and reduced GSH contents and superoxide dismutase activities, thus promoting high level of oxidative stress, which may be a pivotal mechanism underlying As₂O₃ cocarcinogenic action.     

DFT and MD study of adsorption sensitivity of aluminium phosphide nanotube towards some air pollutant gas molecules

To investigate the adsorption behaviour of CS₂, CO₂, SO₂, H₂Se and H₂S gas molecules on the external surface of (6, 0) single-walled aluminium phosphide nanotube (AlPNT), the density functional theory (DFT) calculations at the B3LYP level of theory are performed. The partial densities of states (PDOS) for the SO₂ molecule, the S and O atoms of SO₂ molecule before and after adsorption on the surface of AlPNT have been plotted. The vibrational frequencies and physical properties such as chemical potential, chemical hardness, dipole moment and chemical electrophilicity of all studied complexes have been systematically investigated. The electron density and the Laplacian of the electron density for bond critical points have been examined by the AIM theory. Also the molecular dynamics (MD) simulations of two complexes with the minimum and maximum negative interaction energies that is: AlPNT/CO₂ and AlPNT/SO₂ complexes, respectively, have been considered.     

(−)‐Epicatechin rescues the As2O3‐induced HERG K+ channel deficiency possibly through upregulating transcription factor SP1 expression

(?)‐Epicatechin (EPI) has beneficial effects on the cardiovascular disease. The human ether‐a‐go‐go‐related gene (HERG) potassium channel is crucial for repolarization of cardiac action potential. Dysfunction of the HERG channel can cause long QT syndrome type 2 (LQT2). Arsenic trioxide (As₂O₃) has shown efficacy in the treatment of acute promyelocytic leukemia. However, As₂O₃ can induce the deficiency of HERG channel and cause LQT2. In this study, we examined whether EPI could rescue the As₂O₃‐induced HERG channel deficiency. We found that 3 μM EPI obviously increased protein expression and current of HERG channel. EPI was able to recover the protein expression and current of HERG channel disrupted by As₂O₃. EPI was able to increase the expression of SP1 protein and recover the expression of SP1 protein disrupted by As₂O₃. In addition, EPI significantly shortened action potential duration prolonged by As₂O₃. Our data suggest that EPI rescues As₂O₃‐induced HERG channel deficiency through upregulating SP1 expression.