► The inhibitive action of 1,8-bis (1-chlorobenzyl-benzimidazolyl)-octane for mild steel in different concentration HCl solution was studied by weight loss, electrochemical methods and SEM. The ...following principle conclusions can be deduced: ► The corrosion of mild steel in HCl medium is effectively reduced by the addition of CBO. ► The compound acts as a mixed-type inhibitor and obeys Langmuir adsorption isotherm. ► Cl
− plays an interconnecting bridge role between steel surface and cationic inhibitor. ► The inhibitor has excellent inhibiting properties in HCl solution.
The influences of a benzimidazole derivative, namely 1,8-bis (1-chlorobenzyl-benzimidazolyl) -octane (CBO) on the corrosion behaviour of mild steel in different concentration HCl solutions were studied by weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) measurements and SEM observations. The results showed that CBO acted as an excellent and a mixed-type inhibitor via strongly chemical adsorption onto mild steel surface to suppress simultaneously both anodic and cathodic processes according to the Langmuir adsorption isotherm. Inhibition efficiencies increased with increasing concentration of inhibitor and HCl. An inhibition mechanism was proposed in terms of strongly adsorption of inhibitor molecules on mild steel surface.
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► An imidazoline derivative can effectively inhibit carbon steel corrosion in alkaline solution. ► The compound acts as a cathodic type inhibitor by retarding the reduction of oxygen. ...► The N
C–N region in imidazoline ring is the most active adsorption site. ► Adsorption of inhibitor takes parallel to metal surface with high interaction energy. ► Theory calculation and MD simulation can give an insight into the inhibition mechanism.
The inhibition activity of an imidazoline derivative, namely 1-N,N′-bis(hydroxylethylether)-aminoethyl-2-stearicimidazoline (HASI) for carbon steel in 5% NaCl saturated Ca(OH)
2 solution was investigated using electrochemical measurements in conjunction with Raman and Fourier transform infrared (FTIR) spectroscopy techniques. Quantum chemical calculations and molecular dynamic (MD) simulations were applied to analyze the experimental data and elucidate the adsorption behavior and inhibition mechanism of inhibitor. The results indicate that HASI is an effective inhibitor in protecting carbon steel from corrosion in alkaline chloride solution and acts as a cathodic type inhibitor with the dominant suppression of cathodic reduction of oxygen. The inhibition behavior of HASI is strongly related to its adsorption activity on carbon steel surface, which leads to an enhancing in the corrosion resistance of carbon steel and a reduction in the corrosion rate. Density functional theory (DFT) calculations suggest that the N
C–N region in imidazoline ring is the most active reaction site for the inhibitor adsorption on metal surface via the donor–acceptor interactions between the lone electron pairs on nitrogen atoms together with the π-electrons of heterocyclic and the vacant d orbital of iron atoms. The adsorption of inhibitor on three typical surfaces (Fe (1
0
0), F
2O
3 (1
1
0) and F
3O
4 (1
0
0)) takes nearly parallel to the surface so as to maximize its contact with the surface, as shown as the MD simulations. The experiments incorporating the theoretical calculation and MD simulation can provide an insight into the understanding of interactions between the inhibitor molecules and the carbon steel surfaces.
Cores from the middle Eocene sediments of the Dongying Depression of the southern Bohai Bay Basin in east China yield various kinds of sedimentary deformation structures. They include microfolds, ...load casts, flame structures, ball-and-pillow structures, load-cast ripples, pinch-and-swell structures, boudinage structures, sand dikes, microfaults, and cataclastic breccias. Gravity flows, including turbidites and debris flows, also occur in the study area. The deformation layers can be divided into plastic deformation and brittle deformation types. These develop in a succession composed mainly of dark finely laminated and massive mudstone interbedded with thin sandstones and carbonate rocks that accumulated in a low-energy semi-deep to deep lacustrine environment in a tectonically active setting. Considering the facies attributes in the study area, intrinsically possible trigger mechanisms such as rapid sediment loading and storm currents are absent. Thus, the sedimentary deformation features should be induced by seismic activity, and the same with the gravity flows. These seismites are interpreted to have originated from earthquakes with magnitudes exceeding M 5.6. Basin-controlling faults in the north border of Dongying Depression give rise to the occurrence of seismites. The increasing occurrence frequency of seismites from Es4u to Es3l corresponds with the increase in the activity velocity of the basin-controlling faults. Compared with the seismites developed in other fault depressions in the Bohai Bay Basin, seismites developed in the Dongying Depression are relatively smaller scale and are dominated by microfault layers, relatively more cohesive sediments, and greater distance between seismites and active faults results in the occurrence of these features.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Amino acid transporters in plants are crucial for distributing amino acids between plant organs and cellular compartments. The H⁺‐coupled plasma membrane transporter CAT1 (cationic amino acid ...transporter 1) facilitates the high‐affinity uptake of basic amino acids. The uptake of lysine (Lys) via the roots was not altered in loss‐of‐function mutants, in accordance with the minor expression of CAT1 in roots, but plants ectopically overexpressing CAT1 incorporated Lys at higher rates. Exogenous Lys inhibited the primary root of Arabidopsis, whereas lateral roots were stimulated. These effects were augmented by the presence or absence of CAT1. Furthermore, the total biomass of soil‐grown plants ectopically overexpressing CAT1 was reduced and the time to flowering was accelerated. These effects were accompanied by only minor changes in the overall amino acid profile. Interestingly, CAT1 belongs to a specific small cluster of nitrogen‐containing metabolite transporter genes that are rapidly up‐regulated upon infection with Pseudomonas syringae and that may participate in the systemic response of plants to pathogen attack. The overexpression of CAT1 indeed enhanced the resistance to the hemibiotrophic bacterial pathogen P. syringae via a constitutively activated salicylic acid (SA) pathway, which is consistent with the developmental defects and the resistance phenotype.
A cationic gemini-surfactant, namely 1,4-bis (1-chlorobenzyl-benzimidazolyl)-butane (CBB) was synthesized and its inhibition effect on the corrosion of mild steel in 0.5
M HCl solution was ...investigated by weight loss and electrochemical techniques. The results showed that CBB acts as an excellent corrosion inhibitor in 0.5
M HCl by suppressing simultaneously the cathodic and anodic processes via chemical adsorption on the surface of steel, which followed the Langmuir adsorption isotherm. The inhibition efficiency increased with the increase of CBB concentration and temperature. The adsorption mechanism of the compound was discussed in terms of thermodynamic and kinetic parameters deduced from the experimental data.
This study presents a combined electrochemical and X-ray photoelectron spectroscopy (XPS) surface analytical investigation on the natural passivation process and its effect on Cl− induced corrosion ...resistance of traditional carbon steel, ferritic and austenitic stainless steels (SSs) (i.e. HRB400 steel, 430 and 304 SSs) in simulated concrete pore solution (SPS). It was found that a complete and more compact passive film with a stratified structure could be naturally formed on the tested steel surfaces after different immersion time. The chemical composition of the passive film and its corrosion resistance strongly depended on the alloying element and natural passivation time. For HRB400 steel, the outer layer of natural passive film was mainly composed of Fe3+ species and the inner layer was predominated by Fe2+ ones, while the outer layer of natural passive film formed on SSs surface consisted of Fe and Cr oxides and hydroxides, enriched in Fe3+ species, and an inner layer was made of mixed Fe2+ and Cr3+ oxides (enriched in Fe2+ species). The natural pre-passivation could effectively improve the Cl− induced corrosion resistance of three steels. Compared with HRB400 steel, both austenitic and ferritic SSs exhibited the better corrosion resistance due to the formation of Cr-enriched passive film, of which, 304 SS had the highest pitting corrosion resistance.
Although recognized in small molecules for quite some time, the implications of halogen bonding in biomolecular systems are only now coming to light. In this study, several systems of proteins in ...complex with halogenated ligands have been investigated by using a two-layer QM/MM ONIOM methodology. In all cases, the halogen−oxygen distances are shown to be much less than the van der Waals radius sums. Single-point energy calculations unveil that the interaction becomes comparable in magnitude to classical hydrogen bonding. Furthermore, we found that the strength of the interactions attenuates in the order H ≈ I > Br > Cl. These results agree well with the characteristics discovered within small model halogen-bonded systems. A detailed analysis of the interactions reveals that halogen bonding interactions are responsible for the different conformation of the molecules in the active site. This study would help to establish such interaction as a potential and effective tool in the context of drug design.
The CCR5 chemokine receptor acts as a co-receptor for HIV-1 viral entry. Here we report the 2.7 angstrom-resolution crystal structure of human CCR5 bound to the marketed HIV drug maraviroc. The ...structure reveals a ligand-binding site that is distinct from the proposed major recognition sites for chemokines and the viral glycoprotein gp120, providing insights into the mechanism of allosteric inhibition of chemokine signaling and viral entry. A comparison between CCR5 and CXCR4 crystal structures, along with models of co-receptor—gp120-V3 complexes, suggests that different charge distributions and steric hindrances caused by residue substitutions may be major determinants of HIV-1 co-receptor selectivity. These high-resolution insights into CCR5 can enable structure-based drug discovery for the treatment of HIV-1 infection.
G-protein-coupled receptors (GPCRs) signal primarily through G proteins or arrestins. Arrestin binding to GPCRs blocks G protein interaction and redirects signalling to numerous G-protein-independent ...pathways. Here we report the crystal structure of a constitutively active form of human rhodopsin bound to a pre-activated form of the mouse visual arrestin, determined by serial femtosecond X-ray laser crystallography. Together with extensive biochemical and mutagenesis data, the structure reveals an overall architecture of the rhodopsin-arrestin assembly in which rhodopsin uses distinct structural elements, including transmembrane helix 7 and helix 8, to recruit arrestin. Correspondingly, arrestin adopts the pre-activated conformation, with a ∼20° rotation between the amino and carboxy domains, which opens up a cleft in arrestin to accommodate a short helix formed by the second intracellular loop of rhodopsin. This structure provides a basis for understanding GPCR-mediated arrestin-biased signalling and demonstrates the power of X-ray lasers for advancing the frontiers of structural biology.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
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