• Membrane Journal
• /
• v.15 no.1
• /
• pp.8-14
• /
• 2005

The hyaluronic acid (HA) with excellent biocompatibility can be combined with the monomer polylactide with good biodegradability to produce biocompatible materials which can control the period of degradation in a human body. By freeze drying method, HA and the lactic acid, monomer of polylactide, or lactide, the ester dimer of polylactide, were crosslinked with crosslinking agent, l-ethyl-3-(3-dimethyl aminopropyl) carbodiimide. The analysis of infrared spectroscopy showed that the ester linkage was formed and the analysis of nuclear magnetic resonance (NMR) spectroscopy showed that the ester linkage was due to the reaction of lactic acid and HA. The conversion (6∼32%) and degree of crosslinking (4∼19%) increased but the selectivity was almost constant at 62% as the mole ratio of LA to HA increased from 1 to 10 in the crosslinking reaction. The brittleness became more pronounced and the rate of degradation became faster with more addition of lactic acid resulting from the higher ratio of LA to HA, and the swelling ratio was in the range of 500 to 2000%.

• Journal of the Korean Chemical Society
• /
• v.55 no.5
• /
• pp.830-834
• /
• 2011

This paper is on the industrial synthesis process of anti-oxidant RD ((2,2,4-trimethyl-1,2-dihydroquinoline polymer $(C_{12}H_{15}N)_n$. n=2-4)).The content of dimer, trimer and tetramer of RD as the inspection targets, using the orthogonal design method - take the ratios of keto-amine, the reaction time, the reaction temperatures and the ratios of catalyst acid-amine as inspect factors - to optimized the reaction condition. The results indicate that the best ratio of keto-amine is 2:1, the time of salification and condensation is 3 hours and 7.5 hours. The range of temperature of salification and condensation is $135^{\circ}C$ and $120-125^{\circ}C$, and that the best ratio of acid-amine is 0.2: 1 (the proportion is the concentration ratio for mole). Under the optimization conditions, the yield of RD was stabilized and content of RD more than 45%.

• Korean Journal of Microbiology
• /
• v.27 no.4
• /
• pp.348-356
• /
• 1989

An extracellular peroxidase found in culture broth of Pleurotus ostreatus was induced by syringic acid. This enzyme was fractionated by DEAE Sephadex A-50 ion exchange chromatography and gel filtration chromatogrphy on Sephadex G-150. The enzyme is a glycoprotein containing 35.7% carbohydrate. The results of SDS-linear polyacrylamide gradient gel electrophoresis and gel filtration indicate that the enzyme is a dimer consisted of identical subunits (Mr=72,400). The absorption spectrum of the enzyme indicates the presence of one mole of iron protoporphyrin IX per one mole of subunit. Isoelectric point of the enzyme is 4.26 and $K_m$ values for $H_2O_2$ is $7.2{\mu}M$. The enzyme showed its optimal activity at pH 3.5-4.0 and at $40^{\circ}C$. The Km values of this enzyme for ferulic acid and sinapic acid are 2.4 and 12.3 times higher than those of horseradish peroxidase, respectively.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.4
• /
• pp.1153-1159
• /
• 2013

A novel solid-contact indium(III)-selective sensor based on bis-(1H-benzimidazole-5-methoxy-2-[(4-methoxy-3, 5-dimethyl-1-pyridinyl) 2-methyl]) thiosulfinate, known as an omeprazole dimer (OD) and a neutral ionophore, was constructed, and its performance characteristics were evaluated. The sensor was prepared by applying a membrane cocktail containing the ionophore to a graphite rod pre-coated with polyethylene dioxythiophene (PEDOT) conducting polymer as the ion-to-electron transducer. The membrane contained 3.6% OD, 2.3% oleic acid (OA) and 62% dioctyl phthalate (DOP) as the solvent mediator in PVC and produced a good potentiometric response to indium(III) ions with a Nernstian slope of 19.09 mV/decade. The constructed sensor possessed a linear concentration range from $3{\times}10^{-7}$ to $1{\times}10^{-2}$ M and a lower detection limit (LDL) of $1{\times}10^{-7}$ M indium(III) over a pH range of 4.0-7.0. It also displayed a fast response time and good selectivity for indium(III) over several other ions. The sensor can be used for longer than three months without any considerable divergence in potential. The sensor was utilized for direct and flow injection potentiometric (FIP) determination of indium(III) in alloys. The parameters that control the flow injection method were optimized. Indium(III) was quantitatively recovered, and the results agreed with those obtained using atomic absorption spectrophotometry, as confirmed by the f and t values. The sensor was also utilized as an indicator electrode for the potentiometric titration of fluoride in the presence of chloride, bromide, iodide and thiocyanate ions using indium(III) nitrate as the titrant.

• Elastomers and Composites
• /
• v.37 no.1
• /
• pp.31-38
• /
• 2002

Polymerization of carboxylated styrene-butadiene latex takes longer time than that of acrylic emulsion due to delocalization of radical in butadiene unit having conjugated double bond. A latex stability is the most important properties owing to use intact without separating polymer from base latex. For reducing polymerization time without decreasing any properties of latex, carbon tetra-chloride which has been used as the most popular chain transfer agent was replaced to combination of tert-dodecylmercaptane and ${\alpha}$-methylstyrene dimer. The replacement yielded reducement or 2 hr in polymerization time. In the increment step, charge amount of acrylic acid was limited to 0.3 part to restrain viscosity enhancement. Just after initial step, addition of 0.1 part acrylamide prevent polymer chain from diffusing between two region followed by giving hardness and final good adhesive force to latex particles.

• Applied Chemistry for Engineering
• /
• v.17 no.3
• /
• pp.321-326
• /
• 2006

Thermal degradation of styrene dimer fraction (SDF, main compound: 47 wt% of 1,3-diphenylpropane), 5~15% of total products produced during decomposition of waste expanded polystyrene (WEPS) was investigated. Reaction condition of $360^{\circ}C$, and 152 kPa to 202 kPa was an optimum for high pressure degradation. Under this operating condition, the yield of oil was 73.8% and the selectivities to Ben, Tol, EB, SM, and AMS were 0.4, 30.9, 15.0, 19.6, and 4.2%, respectively. Non-catalytic fixed bed continuous degradation was conducted at reaction temperatures of $510{\sim}610^{\circ}C$ and contact time ranges of 2~24 min, where the yield was increased by increasing of reaction temperature and contact time. A $Cr_2O_3$ catalyst showed the highest activity and SM yield among acid, base, and redox catalysts. The conversion of 74.6% and the yield of Ben, Tol, EB, SM, and AMS were 0.4, 21.6, 9.7, 17.9, and 3.5%, respectively at $560^{\circ}C$ and contact time of 24 min. It is thought that styrene is converted to EB and other secondary products throughout the formation of diradicals of styrene.

• Journal of Microbiology and Biotechnology
• /
• v.28 no.4
• /
• pp.597-605
• /
• 2018

Acyl-CoA oxidases (ACOXs) play important roles in lipid metabolism, including peroxisomal fatty acid ${\beta}$-oxidation by the conversion of acyl-CoAs to 2-trans-enoyl-CoAs. The yeast Yarrowia lipolytica can utilize fatty acids as a carbon source and thus has extensive biotechnological applications. The crystal structure of ACOX3 from Y. lipolytica (YlACOX3) was determined at a resolution of $2.5{\AA}$. It contained two molecules per asymmetric unit, and the monomeric structure was folded into four domains; $N{\alpha}$, $N{\beta}$, $C{\alpha}1$, and $C{\alpha}2$ domains. The cofactor flavin adenine dinucleotide was bound in the dimer interface. The substrate-binding pocket was located near the cofactor, and formed at the interface between the $N{\alpha}$, $N{\beta}$, and $C{\alpha}1$ domains. Comparisons with other ACOX structures provided structural insights into how YlACOX has a substrate preference for short-chain acyl-CoA. In addition, the structure of YlACOX3 was compared with those of medium- and long-chain ACOXs, and the structural basis for their differences in substrate specificity was discussed.

• Journal of the Korean Chemical Society
• /
• v.34 no.3
• /
• pp.260-266
• /
• 1990

The electrochemical behavior of N-methyl-2-amino-l-cyclopentene-l-dithiocarboxylic acid $(N-CH_3 acdc) and 2-amino-l-cyclopentene-l-dithiomethyl ester (S-CH_3 acdc) in DMF have been investigated by the use of polarography, cyclic voltammetry and coulometry. The dimer of N-CH_3 acdc is further oxidized at +0.98 V via 2-electron process to produce free sulfur atom and cyclization product. The ring formation between two dithio group occurs along with the elimination of one sulfur atom. The elimination of sulfur atom occurs via two electron oxidation process at + 0.98 V vs. Ag/AgCl electrode. However, the cyclization does not occur in the S-CH_3$ acdc.

• Toxicological Research
• /
• v.35 no.2
• /
• pp.161-165
• /
• 2019

Cysteamine has been used in cosmetics as an antioxidant, a hair straightening agent, and a hair waving agent. However, recent studies indicate that cysteamine can act as an allergen to hairdressers. The objective of this study was to develop and validate a simple and effective reversed-phase high-performance liquid chromatography (RP-HPLC) method for the measurement of cysteamine and its dimer, cystamine. Sodium 1-heptanesulfonate (NaHpSO) was used as an ion-pairing agent to improve chromatographic performance. Separation was performed on a Gemini C18 column ($250mm{\times}4.6mm$, $5{\mu}m$ particle size) using a mobile phase composed of 85:15 (v/v) 4 mM NaHpSO in 0.1% phosphoric acid:acetonitrile. UV absorbance was monitored at 215 nm. The RP-HPLC method developed in this study was validated for specificity, linearity, limit of detection, limit of quantitation, precision, accuracy, and recovery. Cysteamine and cystamine were chromatographically resolved from other reducing agents such as thioglycolic acid and cysteine. Extraction using water and chloroform resulted in the recovery for cysteamine and cystamine ranging from 100.2-102.7% and 90.6-98.7%, respectively. This validated RP-HPLC method would be useful for quality control and monitoring of cysteamine and cystamine in cosmetics.

• Molecules and Cells
• /
• v.45 no.7
• /
• pp.495-501
• /
• 2022

Leucine dehydrogenase (LDH, EC 1.4.1.9) catalyzes the reversible deamination of branched-chain L-amino acids to their corresponding keto acids using NAD⁺ as a cofactor. LDH generally adopts an octameric structure with D4 symmetry, generating a molecular mass of approximately 400 kDa. Here, the crystal structure of the LDH from Pseudomonas aeruginosa (Pa-LDH) was determined at 2.5 Å resolution. Interestingly, the crystal structure shows that the enzyme exists as a dimer with C2 symmetry in a crystal lattice. The dimeric structure was also observed in solution using multiangle light scattering coupled with size-exclusion chromatography. The enzyme assay revealed that the specific activity was maximal at 60℃ and pH 8.5. The kinetic parameters for three different amino acid and the cofactor (NAD⁺) were determined. The crystal structure represents that the subunit has more compact structure than homologs' structure. In addition, the crystal structure along with sequence alignments indicates a set of non-conserved arginine residues which are important in stability. Subsequent mutation analysis for those residues revealed that the enzyme activity reduced to one third of the wild type. These results provide structural and biochemical insights for its future studies on its application for industrial purposes.