• Journal of Radiopharmaceuticals and Molecular Probes
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• v.7 no.2
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• pp.85-91
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• 2021

Selective amino acid conjugation of bulky antibodies is a valuable asset for real-time diagnosis and therapy. However, selective conjugation incorporating a chelate-bearing radioactive atom into an antibody without affecting its immunoreactivity is a challenging task. A bifunctional chelator (BFC), a selective amino acid-targeting probe, and a linker have been developed to overcome this problem. Here, we report the synthesis of a novel propylene cross-bridged chelator (PCB)-1,8-N,N'-bis-(carboxymethyl)-1,4,8,11-tetraazacyclotetradecane (TE2A)-luminol BFC via a click reaction and radiolabel it with a ⁶⁴Cu ion for tyrosine-selective conjugation of trastuzumab. In the initial optimization study, we tried different oxidative addition conditions such as electro-oxidation, hemin, horseradish peroxidase, iodogen tube, chloramine-T, and iodo beads. In this study, up to 82% of ⁶⁴Cu-PCB-TE2A-luminol was conjugated with the antibody in an iodo bead-catalyzed oxidative addition reaction with an isolated yield of 24.4%.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.3 no.2
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• pp.54-58
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• 2017

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF MS) is one of the powerful methods that enable analysis of small molecules as well as large molecules up to about 500,000 Da without severe fragmentation. MALDI-TOF MS, thus, has been a very useful an analytical tool for the confirmation of synthetic molecules, probing PTMs, and identifying structures of a given protein. In recent nuclear medicine, MALDI-TOF MS liner ion mode helps researcher calculate the average number of chelator(or linkage) per an antibody conjugate, such as DOTA-(or DFO-) trastuzumab for labeling a medical radioisotope. This simple technique can be utilized to improve the labeling method and control the quality at the development of antibody-based radiopharmaceuticals, which is very effected to diagnosis and therapy for in vivo tumor cells, with radioisotopes like $^{89}Zr$, $^{64}Cu$, and 177Lu. To minimize the error, MALDI-TOF MS measurement is repeatedly performed for each sample in this study, and external calibration is carried out after data collection.

• Korean Journal of Clinical Laboratory Science
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• v.43 no.2
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• pp.33-42
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• 2011

Zinc plays a key role in genetic expression, cell division, and cell growth and is essential for the functions of more than 450 metalloenzyme. There are high concentrations of zinc in pigment epithelium in bullfrog eye. Zinc deficiency causes night blindness and abnormal dark adaptation. The purpose of this study was to identify ERG (electroretinogram) b-wave sensitivity during light and dark adaptation in bullfrog retina after zinc and zinc chelators treatment such as histidine and TSQ (N-(6-methoxy-8-qunolyl)-p-toluenesulfon amide). Especially, we focused whether histidine act as a zinc chelator in the Muller cell. The results of our study are summarized as follows: 1) Both zinc and histidine elevated ERG b-wave amplitude and threshold in Muller cells by accelerating rhodopsin regeneration time and increased a-peak absorbance during light adaptation. 2) TSQ reduced those by prolonging rhodopsin regeneration time and decrement of a-peak absorbance during light adaptation. 3) Zinc shortened rhodopsin regeneration time and prolonged a-peak absorbance. These results suggested that histidine may act as a zinc-mediated transporter in presynaptic Muller cell membrane rather than zinc chelator and acts as a GABA-receptor inhibitor which blocks $Cl^-$ influx to the postsynapse.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.7
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• pp.873-881
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• 2004

This research was aimed to investigate the effect of enzyme and the addition of chelators on rotting of the Kenaf bast. Enzyme rotting was effective only when the chelators were added with the enzyme. EDTA was a more effective chelator than oxalic acid under 1% concentration. There was no difference in the rotting effect under different enzyme concentration levels, and under different treatment time and temperature. Therefore, it was found that enzyme rotting can be carried out with low enzyme concentration(0.125%) at room temperature. Retting time can be shortened when higher enzyme concentration and higher temperature are applied. Cellulose I structure of kenaf fiber did not change after enzyme rotting, and different enzyme concentration did not affect the crytallinity structure. Non-cellulosic matters such as hemicellulose, lignin, and pectin were present in the descending order in the enzyme rotted kenaf fiber, and there were no differences in their amounts due to enzyme concentration levels. There was no difference in the dyeabilities of kenaf fiber rotted with different enzyme concentration levels. Enzyme rotted kenaf fiber showed better cyeability when pectin, lignin, and hemicellulose were removed.

• Bulletin of the Korean Chemical Society
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• v.25 no.12
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• pp.1889-1892
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• 2004

The peroxidase activity of cytochrome c was studied by using a chromogen, 2,2'-azinobis-(2-ethylbenzthiazoline-6-sulfonate) (ABTS). Initial rate of ABTS oxidation formation was linear with respect to the concentration of cytochrome c between 2.5-10 ${\mu}$M and $H_2O_2$ between 0.1-0.5 mM. The optimal pH for the peroxidase activity of cytochrome c was 7.0-8.5. The peroxidase activity retained about 40% of the maximum activity when exposed at 60 $^{\circ}C$. for 10 min. The peroxidase activity showed a typical Michaelis-Menten kinetics for $H_2O_2$ which Km value was 29.6 mM. Radical scavengers inhibited the peroxidase activity of cytochrome c. The peroxidase activity was significantly inhibited by the low concentration of iron chelator, deferoxamine. The results suggested that the peroxidase activity was associated with iron in the heme of cytochrome c.

• Archives of Pharmacal Research
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• v.18 no.3
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• pp.159-163
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• 1995

Previously, we have reported that methylene blue (MB) induces cytotoxicity in human brain tumor cells through the generation of free radicals. In this study the effect of deferoxamine (DFO), an iron chelator, on MB-induced cytotoxicity was investigated using SK-N-MC human neuroblastoma and U-373 MG human astrocytoma cells as model cellular systems. The cytotoxic effect of MB was potentiated by DFO. The potentiation effect of DFO was significantly blocked by either stoichiometric amounts of ferric ion, various antioxidants, hydroxyl radical scavengers or intracellular $Ca^{2+}$ release blockers. These results suggest that hydroxyl radical and intracellular $Ca^{2+}$ may act as important mediators of the enhanced cytotoxicity by MB and DFO. These results further suggest that the combined treatment with MB and DFO may be useful for the therapeutical applications of human brain tumors.

• Korean Journal of Veterinary Research
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• v.47 no.3
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• pp.265-271
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• 2007

This study investigated the protective effects of ethylene glycol-bis(${\beta}$-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA), an extracellular calcium chelator, and ethylenediaminetetraacetic acid (EDTA), which chelates calcium and most metal ions, against carbon tetrachloride ($CCl_4$)-induced acute hepatotoxicity in mice. Mice were treated with EGTA or EDTA at a dose of 20 (low) or 100 mg/kg (high) subcutaneously 1h before $CCl_4$ administration. The mice were fasted and sacrificed 18h after $CCl_4$ treatment. Blood samples were collected from the carotid artery by decapitation under light ether anesthesia. Serum alkaline phosphatase (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), triglyceride (TG), and cholesterol levels were measured. Malondialdehyde (MDA) production was determined as an index of lipid peroxidation in the liver. The liver, kidneys, and spleen were weighed. We also evaluated the histopathological changes in the liver in each group. The relative weights of the liver were significantly higher in the $CCl_4$-treatment group than in the normal group, except in the high-EDTA treatment group. EGTA and EDTA treatment caused a significant decrease in serum ALP, ALT, and AST levels. Of all of the doses of EGTA and EDTA tested, the high-EDTA dose resulted in the most remarkable inhibitory action. The protective effect in the high-EDTA-treatment group was confirmed histopathologically. The low-EGTA-treatment group showed a significant decrease in serum TG and cholesterol levels. Liver MDA levels were significantly decreased in the EGTA (20 mg/kg) and EDTA (20, 100 mg/kg) groups. These results suggest that EDTA, which chelates both calcium and metal ions, confers better protection in $CCl_4$-induced acute liver damage than does EGTA, a calcium chelator.

• Journal of Microbiology and Biotechnology
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• v.18 no.8
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• pp.1357-1363
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• 2008

The $P_{entC}$ promoter of the entCERA operon encoding enzymes for enterobactin biosynthesis in Escherichia coli is tightly regulated by the availability of iron in the culture medium. In iron-rich conditions, the $P_{entC}$ promoter activity is strongly repressed by the global transcription regulator Fur (ferric uptake regulator), which complexes with ferrous ions and binds to the Fur box 19-bp inverted repeat. In this study, we have constructed the expression vector pOS2 containing the $P_{entC}$ promoter and characterized its repression, induction, and modulation by quantifying the expression of the lacZ reporter gene encoding $\beta$-galactosidase. $\beta$-Galactosidase activities of E. coli transformants harboring pOS2-lacZ were highly induced in the presence of divalent metal ion chelators such as 2,2'-dipyridyl and EDTA, and were strongly repressed in the presence of excess iron. It was also shown that the basal level $\beta$-galactosidase expression by the $P_{entC}$ promoter was drastically decreased by incorporating the fur gene into the expression vector. Since the newly developed iron chelator-inducible expression system is efficient and cost-effective, it has wide applications in recombinant protein production.

• The Korean Journal of Pharmacology
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• v.32 no.3
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• pp.425-431
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• 1996

Human neutrophil elastases (HNElastase, EC 3.4.21.37), a causative factor of inflammatory diseases, are regulated by plasma proteinase inhibitors, alpha-proteinase inhibitor and ${\alpha}_2-macroglobulin$. Under certain pathological conditions, however, released enzymes or abnormal function of inhibitors may cause various inflammatory disease. NSAIDs have been clinically applied for treatment of inflammatory diseases. Inhibition of cyclooxygenase is a known mechanism of action of NSAIDs in the treatment of inflammatory disease. In in vitro experiments, HNElastase was inhibited by naproxen, phenylbutazone, and oxyphenbutazone, but ibuprofen, ketoprofen, aspirin, salicylic acid, and tolmetin did not inhibit elastase. HNElastase was also inhibited by chelating agents, EDTA & EGTA, and tetracyclines. Removal of divalent metal ions by EDTA caused inhibition of elastase, and reconstitution of the metal ions recovered the enzyme activity to a certain level. Frequencies and contours in the Raman spectra of various conditions of human neutrophil elastase undergo drastic changes upon partial removal and/or reconstitution of calcium and zinc ions. The metal ion content dependent activities and change of the contour of the Raman spectrogram suggest us that the mechanism of action of a chelator or chelator-like agents on neutrophil elastase may be related to the conformational change at/or near the active site, especially -C=O radical or -COOH radical.

• Nutrition Research and Practice
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• v.1 no.1
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• pp.29-35
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• 2007

Trace mineral studies involving metal ion chelators have been conducted in investigating the response of gene and protein expressions of certain cell lines but a few had really focused on how these metal ion chelators could affect the availability of important trace minerals such as Zn, Mn, Fe and Cu. The aim of the present study was to investigate the availability of Zn for the treatment of MC3T3-E1 osteoblast-like cells and the availability of some trace minerals in the cell culture media components after using chelexing resin in the FBS and the addition of N,N,N',N'-tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN, membrane-permeable chelator) and diethylenetriaminepentaacetic acid (DTPA, membrane-impermeable chelator) in the treatment medium. Components for the preparation of cell culture medium and Zn-treated medium have been tested for Zn, Mn, Fe and Cu contents by atomic absorption spectrophotometer or inductively coupled plasma spectrophotometer. Also, the expression of bone-related genes (ALP, Runx2, PTH-R, ProCOL I, OPN and OC) was measured on the cellular Zn depletion such as chelexing or TPEN treatment. Results have shown that using the chelexing resin in FBS would significantly decrease the available Zn (p<0.05) $(39.4{\pm}1.5{\mu}M\;vs\;0.61{\pm}10.15{\mu}M)$ and Mn (p<0.05) $(0.74{\pm}0.01{\mu}M\;vs\;0.12{\pm}0.04{\mu}M)$. However, levels of Fe and Cu in FBS were not changed by chelexing FBS. The use of TPEN and DTPA as Zn-chelators did not show significant difference on the final concentration of Zn in the treatment medium (0, 3, 6, 9, $12{\mu}M$) except for in the addition of higher $15{\mu}M\;ZnCl_2$ which showed a significant increase of Zn level in DTPA-chelated treatment medium. Results have shown that both chelators gave the same pattern for the expression of the five bone-related genes between Zn and Zn+, and TPEN-treated experiments, compared to chelex-treated experiment, showed lower bone-related gene expression, which may imply that TPEN would be a stronger chelator than chelex resin. This study showed that TPEN would be a stronger chelator compared to DTPA or chelex resin and TPEN and chelex resin exerted cellular zinc depletion to be enough for cell study for Zn depletion.