• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1185-1188
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• 1998

Layered nanocomposite, SiO2/TiO2 sol pillared clay, has been prepared by the ion exchange reaction of Na' ion in montmorillonite with positively charged mixed SiO2/TiO2 sol. The nanosized sol particles were synthesized by mixing SiO2 sol solution with TiO2 one, which is obtained by acidic hydrolysis of TEOS and TiCl4, respectively. From powder XRD, the basal spacing (d001) of the sample calcined at 400 ℃ was found to be ca. 60 Å, due to the multistacking of nanosized SiO2 and TiO2 sol particles, which was confirmed by the pore size analysis from 129Xe NMR and micropore analysis calculated from nitrogen adsorption. The BET specific surface area shows the value of 684 m2g-1 (Langmuir 1115 m2g-1), which is the highest among various pillared clays ever reported previously, and the total porosity is found to be 0.51 mlg-1, and the pores are mainly composed of micropore with a size of ca. 11.8 Å. This result agrees with the adsorption capacity obtained from water adsorption. According to diffuse reflectance ultraviolet-visible spectroscopy, it is found that the TiO2 particles stabilized in the interlayer space of montmorillonite are quantum-sized of ca. 20 Å.

• Journal of Powder Materials
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• v.25 no.6
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• pp.459-465
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• 2018

Most commercially available detonation nanodiamonds (DNDs) require further processing to qualify for use in biomedical applications, as they often contain many impurities and exhibit poor dispersibility in aqueous media. In this work, DNDs are modified to improve purity and impart a high colloidal stability to the particles. The dispersive and adsorption properties of modified DNDs are evaluated in terms of the suitability of DNDs as carriers for non-steroidal anti-inflammatory drugs (NSAIDs) in transdermal delivery. The study of adsorption on strongly positively and strongly negatively charged DNDs showed their high loading capacity for NSAIDs, and a pronounced relationship between the drugs and the particles' charges. Experiments on long-term desorption carried out with DND/NSAID complexes indicate that the nanoparticles exert a sustained effect on the drug release process.

• Korean Journal of Head & Neck Oncology
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• v.37 no.1
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• pp.1-10
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• 2021

Intensity-modulated radiation therapy (IMRT) using X-rays is a standard technique implemented for treating head and neck cancer (HN C). Compared to 3D conformal RT, IMRT can significantly reduce the radiation dose to surrounding normal tissues by using a highly conformal dose to the tumor. Proton therapy is a type of RT that uses positively charged particles named protons. Proton therapy has a unique energy deposit (i.e., Bragg peak) and greater biological effectiveness than that of therapy using X-rays. These inherent properties of proton therapy make the technique advantageous for HNC treatment. Recently, advanced techniques such as intensity-modulated proton therapy have further decreased the dose to normal organs with a higher conformal dose to the tumor. The usage of proton therapy for HNC is becoming widespread as the number of operational proton therapy centers has increased worldwide. This paper aims to present the current clinical evidence of proton therapy utility to HNC clinicians through a literature review. It also discusses the challenges associated with proton therapy and prospective development of the technique.

• Analytical Science and Technology
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• v.36 no.6
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• pp.281-290
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• 2023

Zidovudine is an antiretroviral agent prescribed for the prevention and treatment of human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS). It is typically recommended to be used in combination with other antiretroviral drugs. Zidovudine has the potential to generate N-nitrosodimethylamine (NDMA) in the presence of dimethylamine and nitrite salt under acidic reaction conditions during the drug manufacturing process. NDMA is a potent human carcinogen that may be detected in drug substances or drug products. An analytical method was developed to determine NDMA in pharmaceuticals including zidovudine using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The analysis involved reversed-phase chromatography on a Kinetex F5 column with a mobile phase comprising water-acetonitrile mixtures. The detection of positively charged ions was conducted using atmospheric pressure chemical ionization (APCI). The calibration curve demonstrated excellent linearity (r = 0.9997) across the range of 1-50 ng/mL with a highly sensitive limit of detection (LOD) at 0.3 ng/mL. The developed method underwent thorough validation for specificity, linearity, accuracy, precision, robustness, and system suitability. This sensitive and specific analytical method was applied for detecting NDMA in zidovudine drug substance and its formulation currently available in the market, indicating its suitability for drug quality management purposes.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.258-263
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• 2023

In this study, conductive polymers and the enzyme tyrosinase (Tyr) were deposited on the surface of a screen printed carbon electrode (SPCE), which can be fabricated as a disposable sensor chip, and applied to the detection of bisphenol F (BPF), an endocrine disruptor with proven links to male diseases and thyroid disorders, using electrochemical methods. On the surface of the SPCE working electrode, which was negatively charged by oxygen plasma treatment, a positively charged conductive polymer, poly(diallyldimethyl ammonium chloride) (PDDA), a negatively charged polymer compound, poly(sodium 4-styrenesulfonate) (PSS), and another layer of PDDA were layered by electrostatic attraction in the order of PDDA, PSS, and finally PDDA. Then, a layer of Tyr, which was negatively charged due to pH adjustment to 7.0, was added to create a PDDA-PSS-PDDA-Tyr sensor for BPF. When the electrode sensor is exposed to a BPF solution, which is the substrate and target analyte, 4,4'-methylenebis(cyclohexa-3,5-diene-1,2-dione) is generated by an oxidation reaction with the Tyr enzyme on the electrode surface. The reduction process of the product at 0.1 V (vs. Ag/AgCl) generating 4,4'-methylenebis(benzene-1,2-diol) was measured using cyclic and differential pulse voltammetries, resulting in a change in the peak current with respect to the concentration of BPF. In addition, we compared the detection performance of BPF using an ionic liquid electrolyte as an alternative to phosphate-buffered saline, which has been used in many previous sensing studies. Furthermore, the selectivity of bisphenol S, which acts as an interfering substance with a similar structure to BPF, was investigated. Finally, we demonstrated the practical applicability of the sensor by applying it to analyze the concentration of BPF in real samples prepared in the laboratory.

• Journal of the Korean Applied Science and Technology
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• v.33 no.3
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• pp.549-559
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• 2016

Korean Black body fowl (Gallus gallus domesticus; Ogae) designated as a natural monument (registration number 265) has been known as a superb traditional Korean medicine. In this study, The production of peptide from the Viscera Waste of Yeonsan Ogae was optimized using commercial protease (bromelain) by response surface methodology under high pressure process. The range of processes was pressure (30 to 100 MPa), reaction time (1 to 5 h), and substrate concentration (10 to 30%, w/v). After reaction, the degree of hydrolysis, distribution of amino acids, and molecular weight of peptides were investigated. As a results, the optimization conditions were pressure 90 MPa, reaction time 3 to 4 h, and the amount of viscera meat 20% (w/v), respectively. The molecular weight of protein hydrolysates was distributed 400 to 1,000 Da. Accordingly we presumed that most products were peptides. Of those peptides, nonpolar or hydrophobic, polar but uncharged, positively charged, and negatively charged amino acids were 42.03, 26.0, 13.3, and 18.6%, respectively. Because higher amount of hydrophobic amino acids, we expected that those products would be able to utilize as the functional food ingredients.

• Analytical Science and Technology
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• v.24 no.4
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• pp.275-281
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• 2011

$AlPO_4$-type material was synthesized by a reaction of $Al(OH)_3$ and H3PO4 with organic templates from wastewater of detergent manufacturer. The surface of material was coated with carboxylate groups by the reaction of succinic anhydride with surface amino groups which were formed by treatment of the material with APTMS. Powder XRD patterns showed the characteristic patterns of $AlPO_4$. Morphology of the material was examined using a SEM and the functional groups were investigated by FT-IR analysis. The surface charge of a aqueous suspension was analyzed: $AlPO_4-NH_2$ has positively charged surface while $AlPO_4$-COOH has negatively charged one. They were used for the removal of toxic metals from aqueous solution. The lead ions were adsorbed on the surface by the formation of complexes with carboxylate of surface and $K_d$ was 91.1 mL/g. In conclusion, the $AlPO_4$-COOH might be applicable in the removal of toxic metal ions from aqueous system.

• Korean Chemical Engineering Research
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• v.43 no.4
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• pp.542-547
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• 2005

Biosorption is considered to be a promising alternative to replace or supplement the present methods for the treatment of dye-containing wastewater. In this study, the protonated biomass of Corynebacterium glutamicum was evaluated for its potential to remove two types of reactive dyes (Reactive Red 4, Reactive Blue 4) from aqueous solution. The uptakes of dyes were enhanced with decrease in the solution pH, which was likely because the biomass functional groups increased at acidic pH and the positively charged sites could bind the negatively charged sulfonate group ($dye-SO_3^-$) of dye molecules. An equilibrium state was practically achieved in 10 hr. The Langmuir sorption model was used for the mathematical description of the sorption equilibrium. The maximum sorption capacities of C. glutamicum biomass for Reactive Red 4 and Reactive Blue 4 were estimated to 112.36 mg/g and 263.16 mg/g at pH 1, and 71.94 mg/g and 155.88 mg/g at pH 3.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.6
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• pp.305-310
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• 2009

$TiO_2$ thin films consisting of positively charged poly (diallyldimethylammonium chloride) (PDDA) and negatively charged titanium (IV) bis (ammonium lactato) dihydroxide (TALH) were successfully fabricated on a poly (methyl methacrylate) (PMMA) by layer-by-layer (LBL) self-assembly method. By the measurement of quartz crystal microbalance (QCM), it was found that as the solution pH of TALH decreased, the deposition volume of TALH increased and the thickness of (PDDA/TALH) thin film coated on the surface of PMMA particles increased. The PMMA particles coated with the coating sequence of (PDDA/TALH)n showed the variation of color changes as a function of the number of bilayer. The number of bilayer (n) of (PDDA/TALH) thin films was 10 and 20, the values of $a^*$ and $b^*$ decreased from those of PMMA particles without coating films and the color changes was shifted to green and blue direction in the $a^*$, $b^*$ chromaticity diagram. And then, the number of n increased to 30 and 40, the values of $a^*$ and $b^*$ increased and the color changes was shifted to red and yellow direction, respectively. Finally the PMMA particles coated with $(PDDA/TALH)_{50}$ thin film showed a little same value of $a^*$ and $b^*$ with the PMMA particles without (PDDA/TALH) thin film.

• Journal of Life Science
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• v.30 no.5
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• pp.420-427
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• 2020

A repebody, an artificial non-immunoglobulin protein scaffold, is expected to be a solution in the search for faster, cheaper, and customizable antibodies. However, the production of medical repebodies remains difficult due to their low yield and the complex purification processes required. The Pseudomonas fluorescens ABC transporter system has been suggested as an efficient and cost-effective method for repebody production, but the total yield is low because of the secreted protein's positive charge; thus, a repebody with a high isoelectric point needs to be changed into a more negatively charged protein for better secretion. To achieve this, we first attached oligo-aspartic acids to the N- and C-terminals of the repebody, but secretion efficiency was not enhanced significantly. Subsequently, we devised an alternative method for improved secretion efficiency by engineering fifteen positively charged amino acids to aspartic acid in the non-antigen binding sites of the repebody to give a high net negative charge. As a result, secretion efficiency was greatly enhanced from 21.2% (wildtype) to 58.5% (negatively supercharged). The negatively supercharged repebody was succussfully produced extracellularly by ABC transporter secretion system in P. fluorescens.