Increasing Inhibitor Concentration Research Articles

Synthesis and study of the inhibitory properties of a new Schiff base for C45 carbon steel in 1 M HCl

A newly Schiff base 1, 13-bis-[(4-dimethylamino) benzaldehyde 4, 7, 10-trioxatridecane-diimine] (DABT) was synthesized and characterized on the basis of the results of FT-IR, mass spectroscopy (MS), 1HNMR and 13CNMR. The desired performance of the organic compound DABT which is easy, inexpensive to prepare and eco-friendly, as a corrosion inhibitor for C45 carbon steel in 1 M HCl medium was evaluated using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) measurements. The results suggest that the corrosion inhibition effectiveness increases with increasing inhibitor concentration and decreases with increasing temperature. The polarization experiments demonstrate that DABT exhibits the characteristics of a mixed-type inhibitor and follows the Langmuir isotherm in its adsorption behavior. Contact angle measurement revealed that the inhibitor on the surface of the carbon steel is hydrophobic. The synergistic effect of DABT has been investigated; inhibitory efficiency rises with increasing concentration of KI by competitive adsorption to form a layer of protection on the metal surface. Energy dispersive X-ray spectroscopy (EDS) combined with scanning electron microscope (SEM) was utilized to interpret the morphological study of the carbon steel surface. A good correlation was found between theoretical [Density functional theory (DFT), molecular dynamics simulation (MDS)] and experimental findings.

Study the Effect of “Di-dodecyl amine” as a Corrosion Inhibitor for Carbon Steel in HCl Medium

Numerous organic compounds have been investigated for their potential to reduce corrosion under various circumstances. This study investigated the effects of di-dodecyl amine, an organic chemical, on carbon steel metal corrosion at different temperatures while HCl acid was present. The examination was carried out using accepted methods for polarization, weight loss, and corrosion process testing. The obtained findings demonstrated that the corrosion rate reduces with increasing inhibitor concentration, leading to increased inhibition efficiency. Furthermore, as shown in the weight loss technique, the corrosion rate lowers with increasing surface coverage with organic inhibitor at 313 °C. In the anodic and cathodic polarization methods, as well as in the inhibition efficiency, it is observed to see the cathodic and anodic curves through which the occurrence of the potential and corrosion current is known. The current and corrosion potential decreases with increasing inhibitor concentration. The amines and methyl motiveless in this inhibitor's composition give it their efficacy since they may coat the metal surface and stop corrosion

Corrosion Inhibition Performance of Brachystegia eurycoma Leaf Extract on Mild Steel in Acid Media

The aim of this work is to investigate the corrosion inhibition of B. eurycoma leaves extract as a natural inhibitor for mild steel corrosion in 3 M H2SO4 solution. The corrosion inhibitory activity was analyzed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The surface roughness and its properties through scanning electron microscopy (SEM). The obtained result from EIS divulges that the gradual increase in inhibitor concentration and time of immersion leads to progressive increase in inhibition efficiency. At the end of 8 hours immersion time and inhibitor concentration of 1000 mg/l the highest inhibition efficiency of (88%) was obtained. The potentiodynamic polarization results indicated that addition of B. eurycoma leaves extracts hindered the reaction rates of anodic and cathodic reactions thereby performing as mixed- type inhibitor. The corrosion current density also revealed that in the presence of B. eurycoma leaves extracts the value of corrosion density reduced considerably from 265.2 \(\mu\) A/cm2 for sample without inhibitor to 67.8 \(\mu\) A/cm2 for sample with inhibitor. Again, it was observed that in the presence B. eurycoma leaves extracts the mechanism of hydrogen (effervescence) evolution was unique whereas the anodic dissolution of iron mechanism experienced the impact of the inhibitor. SEM inspection revealed that the mild steel surface showed smoother and lower damage in the presence of inhibitor. Obvious correlations were found between corrosion inhibition efficiency and some quantum chemical parameters such as energy of highest occupied molecular orbital (EHOMO), energy of lowest unoccupied molecular orbital (ELUMO), energy gap (EL–H) and electronic density etc. The obtained results were further elucidated with frontier molecular orbital theory.

Exploring the Efficacy of Novel Thiohydantoin Derivatives with Arylacetamide Core as Corrosion Inhibitors for Mild Steel in Acidic Medium: Insights from Electrochemical Analysis, Comprehensive Characterization, and Quantum Studies

Two new compounds of Thiohydantoin Derivatives N-(4-nitrophenyl)-2-((5-oxo-4,4-diphenyl-4,5-dihydro-1H-imidazole-2-yl)thio) acetamide and N-(4-fluorophenyl)-2-((5-oxo-4,4-diphenyl-4,5-dihydro-1H-imidazole-2-yl)thio) acetamide symbolized by N-NOITAcetamide and N-FOITAcetamide respectively, were synthesized and characterized by NMR spectroscopy. Their effectiveness in inhibiting mild steel (M-S) corrosion in 1.0 M HCl at 298 K was investigated by potentiodynamic polarisation (PDP), electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM), and surface examinations via energy dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) as well as X-ray photoelectron spectroscopy (XPS). Experimental results have been supported by theoretical studies such as Density Functional Theory (DFT) calculations and Monte Carlo (MC) simulation studies. All findings indicate that inhibitors have a considerable impact on lowering the rate of corrosion, and that the efficiency of the inhibitors rises with the concentration of the inhibitor. Experimental results revealed that the efficacy of the new thiohydantoin derivatives with an arylacetamide nucleus increased with increasing inhibitor concentration, where their inhibition efficiencies reached maximum values of 92.1%, 94.1%, for N-NOITAcetamide and N-FOITAcetamide, at 10−3M, respectively. In addition, the icorr decreased with increasing concentration up to 85 µA cm−2 and 58 for N-NOITAcetamide and N-FOITAcetamide respectively, with a blank as a reference of 1045 µA cm−2, while the efficacy reduces as the temperature increases. The activation and thermodynamic parameters indicated that these products act via chemical adsorption on the mild steel surface. Furthermore, the surface analysis (SEM, EDS, and XPS) confirmed the formation of a protective layer adsorbed on the mild steel surface. Polarization curves indicated that N-NOITAcetamide and N-FOITAcetamide are mixed-type inhibitors. Moreover, the quantum chemical calculation well supports the experimental results.

Pyridazine derivatives as effective anti-corrosion additives for carbon steel in 1 M HCl: Electrochemical, surface and theoretical studies

The study aimed to investigate the corrosion inhibition performance of two new pyridazine derivatives namely ((E)-2-(3-(4-(carboxymethoxy)-3-methoxystyryl)-5-(2-chlorobenzyl)-6-oxopyridazin-1(6H)-yl)acetic acid (CO6) and (E)-6-(4-hydroxy-3-methoxystyryl)pyridazin-3(2H)-one (CO39) for carbon steel (C.S) in 1M HCl by combining electrochemical techniques, surface analysis and theoretical studies. The electrochemical impedance spectroscopy (EIS) data indicated that the inhibitory efficiencies of CO6 and CO39 increased with increasing inhibitor concentration but decreased with increasing temperature, achieving 97.0 % and 95.3 %, respectively. The results of the potentiodynamic polarization (PDP) measurements show that the two pyridazine derivatives acted as mixed inhibitors. In addition, experimental studies have shown that CO6 and CO39 reduce corrosion rates by adsorbing on the steel surface following Langmuir adsorption isotherms. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) indicated that a protective layer had been developed on the surface of the carbon steel, which prevented corrosion from progressing. Quantum chemical computations and the molecular structures of the inhibitors were employed to investigate the mechanism of inhibition. The adsorption of the compounds investigated on C.S was validated by theoretical calculations including density functional theory (DFT) and molecular dynamics simulation (MDS).

Synthesis and evaluation of a novel pyridinyl thiazolidine derivative as an antioxidant and corrosion inhibitor for mild steel in acidic environments

A new synthesized (Z)-2-((3,5-dichloropyridin-2-yl)imino)thiazolidin-4-one (DICPT) was evaluated as an antioxidant and a corrosion inhibitor for mild steel (M.STL) in a 0.5 M HCl solution. The antioxidant activity of newly synthesized DICPT was screened using a DPPH assay, and the results showed that DICPT has good antioxidant activity. Electrochemical assessments were conducted utilizing potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). A new compound, DICPT, was synthesized, and its chemical structure was established and validated through various spectroscopic techniques, including including infrared (FTIR), nuclear magnetic resonance (NMR), and mass spectroscopy. PDP measurements revealed DICPT to be a mixed-type inhibitor. Charge transfer resistance (Rct) increased when inhibitor concentrations increased, according to EIS tests. The inhibition efficiency (%I) showed a corresponding rise with increasing inhibitor concentration, peaking at approximately 94.2 % at 3 × 10−5 M. Langmuir’s adsorption isotherm was found to govern the preferred adsorption mode of DICPT molecules onto the metal surface. UV–visible spectra confirmed the chemical interaction between DICPT molecules and the M.STL surface. AFM investigation indicated the formation of a protective layer on the metal surface, shielding it from corrosive environmental factors. Quantum chemical calculations were compared to experimental results to learn more about how corrosion is stopped and how well it works. Our study demonstrates the innovation of DICPT as a dual-function compound, offering both antioxidant and corrosion protection properties. This research contributes to the development of effective corrosion inhibitors for industrial applications.

Study of The Inhibition Corrosion of Aluminum Metal Using Peppermint Oil in An Acidic Medium

This study included the study of the efficiency of peppermint oil inhibition of aluminum corrosion in acidic medium HCl at concentrations (0.5, 1, 1.5, 2 M) on the corrosion rate in the presence and absence of the inhibitor peppermint oil at different concentrations (1000, 2000, 3000, 4000 ppm).In order to study the effect of changing the temperature (303, 313, 323, 333 K) on the corrosion rate in the absence and presence of the inhibitor, different concentrations of the inhibitor were chosen in addition to the acid concentration (1M). The experiments were carried out using the weight loss method to calculate the erosion rate. The expected heat of adsorption enthalpy was (-29.913 KJ/mol), with a negative sign indicates that the process is exothermic. The value of the free energy of adsorption ranged from (11.086-15.067 KJ/mol. (The results showed that Freundlich adsorption isotherm equation is the best fit to examine the adsorption process, also a scanning electron microscope. Showed the surface of aluminum before and after corrosion according to the results of the study, it was found that the used inhibitor reduces corrosion in acidic media. Its anti-corrosion efficacy also improves with increasing inhibitor concentration and with decreasing temperature.

Corrosion inhibition properties of perimidin-10-one derivatives for steel reinforcement in acidic environments: Experimental and theoretical insights

Perimidin-10-one derivatives are environmentally benign corrosion inhibitors that prevent steel reinforcement from corroding in acidic environments. The inhibitory impact of 8-(2-Hydroxybenzoyl)-7 H-9-(3-methylphenylhydrazono)-pyrrolo[1,2-a] perimidin-10-one and 8-(2-Hydroxybenzoyl)-7 H-9-phenylhydrazono-pyrrolo[1,2-a] perimidin-10-one on steel-reinforced corrosion in an acidic media (2 M HCl) were explored using chemical technique, (TP) Tafel polarization, (EIS) electrochemical impedance spectroscopy, and (EFM) electrochemical frequency modulation method, as well as theoretical research (quantum chemistry analysis and molecular dynamic studies). Also Energy dispersive X-ray and scanning electron microscopy (EDX–SEM) were used to examine the morphology of shielded steel-reinforced concrete. The inhibition efficiency of the inhibitors with increasing inhibitor concentration and reaches a maximum of 89.68 percent at a concentration of 11×10−6 M at 55° C, according to the findings. The examination of potentiodynamic polarization revealed that the two compounds act as a mixed category of inhibitor. The Langmuir and Henry adsorption isotherms were followed by inhibitors adsorption on steel reinforcement surface. Quantum chemical calculations based on density functional theory (DFT) were used to investigate the manner of adsorption of the two compounds on reinforced surface. Molecular dynamic studies were used to determine the adsorption energy of the inhibitors at different temperatures. Also the comparison between the experimental parts was applied. The results clearly show that the two compounds work well as corrosion inhibitors for steel reinforcement in an acidic media. Compound (1) > compound (2) are the percent IE orders of Perimidin-10-one derivatives.

Arachis hypogaea’s concentration effect on AISI 1020 carbon steel for corrosion protection

The effects of inhibitor concentration on the corrosion rate and inhibition efficiency of AISI 1020 steel in an acidic and alkaline environment were investigated by means of weight loss measurement at an interval of 7 days and 14 days. To carry out this investigation, the Arachis hypogaea hull was extracted and concentrated in various weight percentages. The inhibition efficiency increased with the increased concentrations of AISI 1020 steel that were immersed in acidic and alkaline solution in the absence and presence of varying inhibitor concentrations of Arachis hypogaea hull extracts. The corrosion behavior, including the corrosion rate, is meticulously characterized through the corrosion rate analysis. The results showed that there is an increase in inhibition efficiency with an increase in inhibitor concentration and that there is a decrease in inhibition efficiency with an increase in immersion time. The organic inhibitor (Arachis hypogaea hull) produced the best inhibition efficiency of 96.4% at a 30% concentration. From the result obtained, Arachis hypogaea hull extracts revealed that it is best suited for inhibition of corrosion of mild steel in both acidic and alkaline environments. The goal of this research paper is to develop a comprehensive understanding of the corrosion inhibition and adsorption mechanisms associated with the implementation of the Arachis hypogaea hull as a natural corrosion inhibitor.

Inhibitive Action of Sulfide Ions on Corrosion and Enhancing Charge‐Discharge Efficiency of Zinc and Zinc‐Indium Alloy as Anode for Alkaline Batteries

AbstractThe obtained data reveal that the coverage of surface (θ) and protection efficiency (η%) for the studied electrodes increases gradually as the inhibitor concentration increases. Tafel plot is carried out at variant temperatures in the investigated basic electrolyte containing 1×10−1 M of S ions. This study reveals that the activation energy barrier of the studied alloy is higher than that of pristine zinc anode at a fixed inhibitor concentration. It is observed that ▵Goads. and η% values rise with rising solution temperature, indicating that S ions adsorption on the studied electrode surfaces occurs by a chemisorption mechanism. Other calculations are made for the additional thermodynamic parameters such as ▵Hoadsand ▵Soads. The zinc anodes get more efficient when S ions are added to the solution, considerably decreasing electrochemical polarization. In addition, the presence of indium sulfide improves the exposed surface area of the alloy, supplying additional improvement in charge‐discharge efficiency. Density functional theory (DFT) is utilized to extract the quantum data to acquire a deeper understanding of the chemical processes between sulfide ions at the interface.

Exploring the effectiveness of two triazole derivatives as copper corrosion inhibitors in NaCl solution: A combined approach of quantitative chemistry and dynamic molecular simulations

The present study investigates the effectiveness of a novel inhibitor, 2‑hydroxy-5-((4-(hydroxymethyl)-1H-1,2,3-triazol-1-yl)methyl) benzaldehyde (STR), in preventing copper from corrosion in a 3.5 wt.% NaCl solution. A comparative study of the inhibition efficiency between our newly synthesized water-soluble triazole STR, and the commercially available Benzotriazole (BTA) was evaluated using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) tests. The results revealed a substantial reduction in the rate of copper oxidation with increasing inhibitor concentrations. At 10−3 M, STR and BTA demonstrated inhibition efficiencies of 92.73% and 97.62% respectively. Analysis of the Tafel curves showed that the inhibitors used exhibited mixed type behavior. Langmuir isotherms showed that the STR and BTA molecules are adsorbed on copper surface, following the chemical adsorption process. Theoretical calculations based on density functional theory (DFT) method and molecular dynamic (MDS) simulations, provided valuable insights into the efficacy and mode of action of STR and BTA as copper corrosion inhibitors in a 3.5 wt.% NaCl solution.

Imidazole-based ionic liquid as a corrosion inhibitor for aluminum alloy and it’s composite in HCl – A comparative study

The corrosion inhibition characteristics of ionic liquid 1-butyl-3-methyl-1H-imidazol-3-ium hexafluorophosphate (BMIF) on the corrosion behavior of 6061 Al–10 vol(%) SiC(p) composite (6061 Al-CM) and 6061 aluminum alloy(base alloy) were studied at different temperatures in 0.1 M HCl medium. The potentiodynamic polarisation technique and AC impedance spectroscopy (EIS) were used for corrosion rate determination. The obtained results showed that inhibition efficiencies increased with the increase in inhibitor concentration and temperature. The adsorption of BMIF on both 6061 Al–CM and base alloy was through chemisorption obeying the Freundlich adsorption isotherm. From the adsorption data thermodynamic parameters were evaluated. Surface morphology studies confirmed the adsorption of BMIF. Maximum inhibition efficiencies were 78 % for 6061 Al-CM and 68 % for base alloy for the concentration of 50 ppm BMIF in 0.1 M HCl at 323 K.

BMPD-Assisted Enhancement of Corrosion Resistance of Carbon Steel: Experimental and First-Principle DFTB Insights

Green corrosion inhibitors are gaining recognition for their sustainable, cost-effective, and environmentally friendly nature, along with their impressive water solubility and high corrosion inhibition efficiency. They offer a promising solution to combat corrosion issues that plague various industries. However, to harness the full potential of these eco-friendly corrosion inhibitors, a profound understanding of their development and underlying mechanisms is essential. This knowledge is the key to paving the way for the next generation of corrosion protection materials. Herein, a comprehensive study was conducted to understand the adsorption, corrosion inhibition efficiency, and stability of 3-benzoyl-4-hydroxy-2,6-bis(4-methoxyphenyl)-4-phenylcyclohexane-1,1-dicarbonitrile (BMPD). This study investigated the performance of BMPD applied to carbon steel (CS) in 1 M hydrochloric acid (HCl) solution. The corrosion inhibition effect was examined using weight loss, potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), and theoretical studies. The surface morphology was also characterized and Tafel polarization analysis shows that BMPD is a mixed inhibitor. The results obtained by electrochemical impedance spectroscopy indicate that the inhibitory effect increases with increasing inhibitor concentration. The adsorption of BMPD on a CS surface obeyed the Langmuir adsorption isotherm. Thermodynamic parameters were calculated and discussed. Furthermore, this study involved a comprehensive computational analysis of the BMPD compound. Using quantum chemical calculations and first-principle simulations, we delved into the structural and electronic properties of BMPD as well as the interfacial adsorption mechanisms between the studied molecule and the iron surface.

Comparative study on the inhibition effect of three inhibitors on the flame propagation of aluminum alloy dust cloud

To investigate the inhibitory effects of NH4H2PO4, NaCl, and CaCO3 on the flame propagation of aluminum alloy dust, an orthogonal experimental approach was employed. The concentrations(C) and particle sizes of the inhibitors were systematically altered to explore variations in inhibitory effects across different scales and to investigate their thermal decomposition characteristics. The results indicate that increasing inhibitor concentration and decreasing particle size serve to decelerate and shorten the flame propagation of aluminum alloy dust. During the inhibition process, the "concentration effect" and the impact of particle "size effect" of the inhibitors become more prominent, resulting in a non-linear reduction in both flame propagation distance and flame velocity. Notably, inhibitory effects are more pronounced when the concentration of NH4H2PO4 exceeds 80%, compared to NaCl. Conversely, when the concentration falls below this threshold, NH4H2PO4 is less effective than NaCl. However, in terms of the "concentration effect," both NH4H2PO4 and NaCl outperform CaCO3. A crucial transition in inhibitory effects is observed at particle sizes near 20 μm, with a significant increase in inhibition efficacy below 20 μm. Among the inhibitors, NH4H2PO4 exhibits the highest level of inhibition, followed by NaCl, while CaCO3 displays the weakest inhibitory effect.

Activation of Ostwald ripening and electrical conductivity in polyHIPEs through the addition of ascorbic acid to graphene-stabilized emulsions

Ascorbic acid was employed to increase the sphere-to-sphere contact of polyHIPEs. Adding a radical inhibitor to the aqueous phase of a graphene-stabilized water-in-oil emulsion was hypothesized to delay the formation of a polymer skin around the dispersed droplet, leading to intimate contact between the surfactant-stabilized drops. Optical microscopy analysis of samples made with varying ascorbic acid concentrations showed decreased sphere size and increased size dispersity at increasing inhibitor concentrations. Electrical conductivity measurements showed an increase at low concentrations of ascorbic acid but a decrease in conductivity at higher concentrations. Our results suggest that the presence of an inhibitor does delay the formation of the polymer skin and allows more intimate contact between spheres, but at higher concentrations, it leads to Ostwald ripening. Scanning electron microscopy of polystyrene/graphene composites revealed that the inhibitor also stopped the polymerization of aqueous-dispersed monomer, leading to polymer patches on the interior of the spheres.

Corrosion mitigation of mild steel in 1 M HCl acid using an expired drug: An experimental approach

The research undertaken highlights the effectiveness of pharmaceutical drug Phenobarbitone (5-Ethyl-5-phenyl-1,3-diazinane-2,4,6-trione) (PB) as inhibitor to mitigate corrosion of mild steel (MS) in 1 M HCl. Corrosion studies were done by electrochemical techniques including potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) in the absence and presence of the Phenobarbitone (PB) drug. Kinetic parameters were calculated by studying the corrosion rate at different temperatures. Results were fitted into suitable adsorption isotherm and from the adsorption data thermodynamic parameters were computed and discussed in detail. Surface morphology studies were conducted using scanning electron microscopy (SEM), electron-dispersive X-ray (EDAX), and atomic force microscopy (AFM) techniques. The nature of the protective layer formed over the metal was studied by measuring the contact angle (CA), which demonstrated the formation of the adsorbed inhibitor layer. Inhibition efficiency increased with increase in concentration of inhibitor and with increase in temperature. For the addition of 0.04 gL-1, the maximum corrosion inhibition efficiency of 78.3 % was achieved at 313 K. Inhibitor acted as a mixed inhibitor with more control over the anodic reaction. Increase in efficiency with increase in temperature suggested the possibility of chemical adsorption. Inhibitor obeyed Langmuir adsorption isotherm, supporting chemical adsorption. Surface morphology clearly demonstrated the formation of barrier film on the surface of metal which prevented further dissolution of metal thereby decreasing the corrosion rate.

Two novel phosphoramide derivatives moiety as corrosion inhibitor for mild steel: Experimental and theoretical study

Two novel phosphoramide containing thiazole derivatives with the name of bis(5‐amino‐1,3,4‐thiadiazol‐2‐yl) phenylphosphonotrithioate (C1) and O, O‐diethyl (5‐((diethoxyphosphorothioyl) thio)‐1,3,4‐thiadiazol‐2yl) phosphoramidothioate (C2) as corrosion inhibition were synthesized and identified by 1H NMR, 13C NMR, 31P NMR, IR, and mass spectroscopies. The electrochemical behavior of mild steel (MS) in hydrochloric acid 1‐M (HCl) solution was perused in the absence and presence of C1 and C2. To determine corrosion inhibition of phosphoramide compounds, scanning electron microscopy (SEM), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) were used. The EIS results show that the charge transfer resistance increases with the addition of inhibitors to the hydrochloric acid solution. The most inhibitor efficiency was 89%, which demonstrated the appropriate anti‐corrosion property of C1. EIS results show better charge transfer resistance on the surface of MS at increased inhibitor concentrations. The PDP analysis showed that C1 and C2 are mixed‐type inhibitors. The PDP examination appeared that C1 and C2 are mixed‐type inhibitors. To way better get the comes about of corrosion inhibition and structure of target compounds, the highest occupied molecular orbital (HOMO) and least unoccupied molecular orbital (LUMO) energies, hardness, dipole moment, and electrophilicity index of synthesized compounds were explored computationally using the density functional theory (DFT) strategy. The hypothetical comes about in great understanding with the exploratory information.

Corrosion behavior of mild steel in 1 M HCl with Cyclotrichium niveum as a green inhibitor

Recently, green inhibitors are replacing classical inhibitors in the acid cleaning industry due to very low cost, environmentally friendly and none toxic. In this study, Cyclotrichium niveum is used as a potential green corrosion inhibitor to investigate the corrosion behavior of mild steel (MS) in chloride solution using electrochemical, morphological, structural and quantum chemical methods. Fifty-three flavonoids are detected in methanol extract of cyclotrichium niveum by LC/ESI-MS/MS. While icorr values decreased, Rp and inhibition efficiencies values derived from electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) increased in increasing inhibitor concentrations. Maximum inhibition efficiency is found to be 97.3%, that is the almost highest value, when compared to previous studies and plant extract is classified as a mixed type inhibitor with respect to the potentiodynamic polarization (PDP). The model that best fits the experimental values is the Langmuir isotherm. The temperature effect is also studied in the range of 25–55 ○C. Higher activation energy is obtained in the presence of inhibitor, suggesting that it acts as an efficient inhibitor by forming a physical barrier to the charge and mass transfer reaction, leading to reduction in corrosion rate. Scanning electron and atomic force microscopies showed the more uniform, crack and pits free structure, confirming that there is a protective film over the MS surface for inhibited solution. XPS analysis showed the existence of C, O, and Fe atoms on the MS surface. Quantum chemical calculation manifested the adsorption mechanism associated with the electronic structure of the molecules. The findings of this work can be applicable in chemical cleaning process with acid treatment.

[Inhibition of GMA-induced ubiquitination process in 16HBE malignantly transformed cells on protein CD44 and MMP14].

To observe the effect of the ubiquitination process on the expression of CD44 antigen(CD44) and matrix metalloproteinase-14(MMP14) in human bronchial epithelial(16HBE) malignantly transformed cells induced by glycidyl methacrylate(GMA). Successfully resuscitated 16HBE cells were cultured using a final concentration of 8 μg/mL GMA as the treatment group and 1 μg/mL dimethyl sulfoxide as the solvent control group, each time stained for 72 h, and then stained again after an interval of 24 h. After repeating the staining three times, the cells were cultured in passages respectively. The 40th generation(P40) GMA-treated group and the same-generation solvent control group were subjected to soft agar colony formation assay and concanavalin A(ConA) agglutination test to confirm that the 40th generation of GMA-induced malignant transformed 16HBE cells possessed malignant transformed cell characteristics.5, 10, 20, 40, 60 μmol/L anacardic acid were used to inhibit the ubiquitination process of GMA-induced malignant transformed 16HBE cells. The protein expression of CD44 and MMP14 were detected by western blotting, while the transcript levels of CD44, MMP14, and TFAP2A were assessed by real-time fluorescence quantitative PCR(qPCR). (1) In the soft agar colony formation assay, the number of clones formed by the cells in the solvent control group was 22, and the number of clones created by the malignantly transformed cells in the GMA-treated group was 208. In the ConA agglutination test, the cells in the solvent control group were uniformly dispersed in ConA solution, and no obvious agglutination occurred for 30 min, whereas the cells in the GMA-treated group were agglutinated in the 5th min, and the agglutinated cells were larger and more rapidly agglutinated. The agglomerates were more significant and faster, and the sensitivity of agglutination was increased. (2) After differential inhibition of GMA-induced ubiquitination in malignantly transformed 16HBE cells, the expression levels of CD44 and MMP14 were reduced in GMA-induced malignantly transformed 16HBE cells compared with the control group(P<0.05). The transcript levels of MMP14 and CD44 decreased with increasing inhibitor concentration(P<0.05), and the transcript levels of the upstream transcription factor TFAP2A were also simultaneously reduced(P<0.05). Inhibition of the cellular ubiquitination process mediates the down-regulation of protein expression and transcriptional expression of CD44 and MMP14 in GMA-induced malignantly transformed 16HBE cells.

Molecular noise-induced activator-inhibitor duality in enzyme inhibition kinetics.

Classical theories of enzyme inhibition kinetics predict a monotonic decrease in the mean catalytic activity with the increase in inhibitor concentration. The steady-state result, derived from deterministic mass action kinetics, ignores molecular noise in enzyme-inhibition mechanisms. Here, we present a stochastic generalization of enzyme inhibition kinetics to mesoscopic enzyme concentrations by systematically accounting for molecular noise in competitive and uncompetitive mechanisms of enzyme inhibition. Our work reveals an activator-inhibitor duality as a non-classical effect in the transient regime in which inhibitors tend to enhance enzymatic activity. We introduce statistical measures that quantify this counterintuitive response through the stochastic analog of the Lineweaver-Burk plot that shows a merging of the inhibitor-dependent velocity with the Michaelis-Menten velocity. The statistical measures of mean and temporal fluctuations - fractional enzyme activity and waiting time correlations - show a non-monotonic rise with the increase in inhibitors before subsiding to their baseline value. The inhibitor and substrate dependence of the fractional enzyme activity yields kinetic phase diagrams for non-classical activator-inhibitor duality. Our work links this duality to a molecular memory effect in the transient regime, arising from positive correlations between consecutive product turnover times. The vanishing of memory in the steady state recovers all the classical results.