• BMB Reports
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• v.28 no.2
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• pp.118-123
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• 1995

Biodegradative threonine dehydratase was purified to homogeneity from Serratia marcescens ATCC 25419 by streptomycin sulfate treatment, Sephadex G-200 gel filtration chromatography followed by AMP-Sepharose 4B affinity chromatography. The molecular weight of the purified enzyme was 118,000 by fast protein liquid chromatography using superose 6-HR. The enzyme was determined to be a homotetrameric protein with subunit molecular weights of 30,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was inhibited by ${\alpha}-Keto$ acids and their derivatives such as ${\alpha}-ketobutyrate$, pyruvate, glyoxlyate, and phosphoenol pyruvate, but not by ${\alpha}-aminobutyrate$ and ${\alpha}-hydroxybutyrate$. The inhibition of the enzyme by pyruvate and glyoxylate was observed in the presence of AMP. The inhibitory effect of glyoxylate was decreased at high enzyme concentration, whereas the inhibition by pyruvate was independent of the enzyme concentration. The kinetics of inhibition of the enzyme by pyruvate and glyoxylate revealed a noncompetitive and mixed-type inhibition by the two inhibitors with respect to L-threonine and AMP, respectively.

• BMB Reports
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• v.36 no.2
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• pp.149-153
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• 2003

The dibucaine number (DN) was determined for serum cholinesterase (EC 3.1.1.8, SChE) in plasma samples. The ones with a DN of 79-82 were used, because they had the "usual" SChE variant. The enzyme was assayed colorimetrically by the reaction of 5,5'-dithiobis-[2-nitrobenzoic acid] (DTNB) with the free sulfhydryl groups of thiocholine that were produced by the enzyme reaction with butrylthiocholine (BuTch) or acetylthiocholine (AcTch) substrates, and measured at 412 nm. Dibucaine, a quaternary ammonium compound, inhibited SChE to a minimum within 2 min in a reversible manner. The inhibition was very potent. It had an $IC_{50}$ of $5.3\;{\mu}M$ with BuTch or $3.8\;{\mu}M$ with AcTch. The inhibition was competitive with respect to BuTch with a $K_i$ of $1.3\;{\mu}M$ and a linear-mixed type (competitive/noncompetitive) with respect to AcTch with inhibition constants, $K_i$ and $K_I$ of 0.66 and $2.5\;{\mu}M$, respectively. Dibucaine possesses a butoxy side chain that is similar to the butryl group of BuTch and longer by an ethylene group from AcTch. This may account for the difference in inhibition behavior. It may also suggest the existence of an additional binding site, other than the anionic binding site, and of a hydrophobic nature.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.27-28
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• 2021

The search for new corrosion inhibitors for different corrosive mediums is a never-ending task. In the present work, the corrosion inhibition behavior and adsorption mechanism of two novel synthetic thiazolidinedione derivatives noted MTZD and ATZD in 3.5 wt.% NaCl solution on copper were investigated. Electrochemical, scanning electron microscope (SEM), atomic force microscopy (AFM) techniques were used along with first-principles DFT calculations. At maximum inhibitor concentration i.e., 300 ppm corrosion inhibition efficiency reached maximum up to 90% and 96% for MTZD and ATZD, respectively, and thereby followed the order of ATZD > MTZD. The inhibition efficiency increased up to 24 h of immersion, and then decreased after 48h immersion. The potentiodynamic curves suggested that the inhibition action of tested compounds is a mixed type of inhibitor. The first-principles DFT calculations suggested that compounds under investigation formed covalent bonds with Cu(111) surface via reactive sites. SEM and AFM results confirmed the formation of protective barrier that prevent corrosion attack.

• Corrosion Science and Technology
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• v.8 no.1
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• pp.1-10
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• 2009

The influence of Schiff bases on the corrosion inhibition of mild steel in 1 M $H_2SO_4$ have been investigated by weight loss, gasometry, impedance and polarization techniques. The results obtained reveal that these compounds act as good inhibitors. The inhibition efficiency of Schiff bases increased with concentration and synergistically increased on addition of chromate, sulphate and halide ions. Potentiodynamic polarization measurements clearly reveal that the investigated inhibitors are of mixed type but they are more cathodic in nature. The adsorption of these compounds on mild steel surface for both the acids were found to obey Langmuir adsorption isotherm. The surface morphology was studied by SEM and UV reflectance spectra.

• BMB Reports
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• v.28 no.4
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• pp.290-292
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• 1995

Existence of a binding site for choline esters with an acyl chain of various sizes was examined by comparing the inhibitory potency of the respective compound. In contrast to acetylcholine, which showed a pure competitive pattern of inhibition, choline esters with an acyl chain of a long size ($C{\geq}5$) expressed a mixed type of inhibition. Binding of choline esters containing a long chain ($C_7-C_{12}$) to the hydrophobic region in the active site is deduced from a linear relationship between the $K_{iE}$ value and the size of acyl moiety, and a good hydrophobicity relationship. In addition, the non-competitive component in the inhibition of acetylcholinesterase seems to be due to the interaction of choline esters with both the hydrophobic site and the trimethylammonium-binding site in the active center of the acetylated acetylcholinesterase.

• Journal of the Korean Chemical Society
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• v.58 no.1
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• pp.85-91
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• 2014

The corrosion behavior of aluminum and mild steel in hydrochloric acid medium was studied using a nicotinic acid hydrazide as inhibitor by potentiodynamic polarization, electrochemical impedance spectroscopy technique and gravimetric methods. The effects of inhibitor concentration and temperature were investigated. The experimental results suggested, nicotinic acid hydrazide is a good corrosion inhibitor for both aluminum and mild steel in hydrochloric acid medium and the inhibition efficiency increased with increase in the inhibitor concentration. The polarization studies revealed that nicotinic acid hydrazide exhibits mixed type of inhibition. The inhibition was assumed to occur via adsorption of the inhibitor molecules on the aluminum and mild steel surface and inhibits corrosion by blocking the reaction sites on the surface of aluminum.

• Corrosion Science and Technology
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• v.5 no.5
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• pp.160-167
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• 2006

S-Acetyl Isothiourea Acetate (S-AITA) was synthesized in the laboratory and this influence on the inhibition of corrosion of mild steel in 1.11 N hydrochloric and 1.12 N sulphuric acids was investigated by weight loss and potentiostatic polarization techniques at 303K, 353K and 403K. These results were confirmed by the impedance technique. The inhibition efficiency increased with increase in concentration of inhibitor and decreased with rise in temperature from 303K to 403K. The maximum inhibition efficiency of S-AITA was found to be 99.95% (0.5% of S-AITA) at 303K in sulphuric acid. The adsorption of this compound on the mild steel surface from the acids has been found to obey Temkin's adsorption isotherm. The potentiostatic polarization results revealed that S-AITA was a mixed type inhibitor. Some thermodynamic parameters i.e., activation energy (Ea), free energy of adsorption (${\Delta}G_{ads}$), enthalpy of adsorption (${\Delta}H$) and entropy of adsorption (${\Delta}S$) were also calculated from weight loss data.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2593-2598
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• 2011

Polyphenols (PPs) are known as antioxidant compounds having benign biological activities. In this paper, a series of hybrid molecules between the free or acetyl protected polyphenol compounds were synthesized and their in vitro antioxidant activity (DPPH assay) and cholinesterase [acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE)] inhibition activities were evaluated. As expected, free phenolic hybrid compounds (6 and 8) showed better antioxidant activity than acetyl protected hybrid compounds (5 and 7) from DPPH assay. But the contrast result was obtained from BuChE inhibition assay. Acetyl protected hybrid compounds (5 and 7) showed better inhibition activity for BuChE than free phenolic hybrid compounds (6 and 8). Specifically, 10 (AcFA-AcFA) were shown as an effective inhibitor of BuChE ($IC_{50}=2.3{\pm}0.3{\mu}M$) and also had a great selectivity for BuChE over AChE (more than 170 fold). Inhibition kinetic studies with acetyl protected compounds (5, 7, 9, and 10) indicated that 5, 7 and 10 are a hyperbolic mixed-type inhibition and 10 is a competitive inhibition type. The binding affinity (Ki) value of 10 to BuChE is $2.32{\pm}0.15{\mu}M$.

• Journal of Electrochemical Science and Technology
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• v.10 no.2
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• pp.231-243
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• 2019

The methanolic extracts of the leaves and stem of the plant Lepidagathis keralensis were evaluated for anticorrosion behavior against mild steel in 1M HCl. Corrosion inhibition studies were done by gravimetric method, electrochemical impedance spectroscopy and potentiodynamic polarization methods. Surface morphology of mild steel in the presence and absence of inhibitors were studied using SEM analysis. UV-Vis studies were also done to evaluate the mechanism of inhibition. Both the extracts showed good inhibition efficiency which increased with increase in concentration of the inhibitor and decreased with increase in temperature. The mechanism of inhibition was explained by adsorption which obeyed Langmuir adsorption isotherm. Thermodynamic calculations revealed a combination of both physisorption and chemisorption of the inhibitor on the surface of mild steel. The extracts behaved as mixed type inhibitors as determined by polarization studies. Quantum chemical studies on Phenoxyethene, one of the major components in the leaf extract of the plant was also carried out to support the experimental results.

• Journal of Acupuncture Research
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• v.29 no.1
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• pp.127-137
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• 2012

Objectives : The purpose of this study is to investigate the effect of $Clematidis$ radix herbal-acupuncture solution, on collagen, adjuvant, lipopolysaccharide and phospholipase A2 induced rheumatoid arthritis in mice. Methods : Arthritis index was measured for mouse that was injected subcutaneously in solution mixed chicken type II collagen with Freund's complete adjuvant. We injected Freund's complete adjuvant into right posterior part of the sole of a ICR mouse foot, which was measured by plethysmometer. The solution mixed $CRHS$ with Tris-HCI, $CaCl_2$, substrate, enzyme was done a chemical action for thirty minutes, and then inhibitory activity of PLA2 enzyme was expressed with inhibition percentage by utilizing isolated arachidonic acid. COX-2 was induced by adding LPS to RAW 264.7 cell, and COX-2 activity was measured by western blot analysis and $PGE_2$ Biotrak kit. Results : $CRHS$ also inhibited Freund's complete adjuvant induced chronic rheumatoid arthritis in mice. $CRHS$ showed significant inhibition of type I and type II $PLA_2$ activities in a dose dependent manner. Furthermore, $PGE_2$ production was decreased with $CRHS$ and lipopolysaccharide-induced COX-2 protein expression was significantly inhibited by $CRHS$. Conclusions : These results suggest that $CRHS$ has an therapeutic effect on drug induced-rheumatoic arthritis by inhibiting $PLA_2$ and COX-2 activities.