Jung-Woo Kim

2-Chloro-4,6-dimethoxy-1,3,5-triazine: A New Effective and Convenient Coupling Reagent for Cephalosporin Derivatives

Abstract Chloro-4,6-dimethoxy-1,3,5-triazine(CDMT) 2 was reacted with 2-(2-amino-4-thiazolyl)-2-syn-alkoxyiminoacetic acid 1 to give an active ester intermediate 3.

Repeated exposure of human fibroblasts to UVR induces secretion of stem cell factor and senescence

Backgroundu2002 Some of chronic hyperpigmentary diseases, such as melasma, induced by multiple factors including chronic sunlight exposure, can recur even after chemical epidermal removal. Dermal factors may be involved in the pathogenesis of melasma. Changes in dermal fibroblasts resulting from chronic sun exposure might cause melanocytes to synthesize melanin in the epidermis.

A Mild and Efficient Tetrahydropyranylation of Alcohols

Abstract Triphenylphosphine (TPP)-iodotrimethylsilane (TMSI) was found to be a convenient and highly effective catalyst for the tetrahydropyranylation of aliphatic and aromatic alcohols with dihydropyran in dichloromethane at ambient temperature.

Properties of a Bacteriocin Produced by Bacillus subtilis EMD4 Isolated from Ganjang (Soy Sauce).

A Bacillus species, EMD4, with strong antibacterial activity was isolated from ganjang (soy sauce) and identified as B. subtilis. B. subtilis EMD4 strongly inhibited the growth of B. cereus ATCC14579 and B. thuringiensis ATCC33679. The antibacterial activity was stable at pH 3-9 but inactive at pH 10 and above. The activity was fully retained after 15 min at 80°C but reduced by 50% after 15 min at 90°C. The activity was completely destroyed by proteinase K and protease treatment, indicating its proteinaceous nature. The bacteriocin (BacEMD4) was partially purified from culture supernatant by ammonium sulfate precipitation, and QSepharose and Sephadex G-50 column chromatographies. The specific activity was increased from 769.2 AU/mg protein to 8,347.8 AU/mg protein and the final yield was 12.6%. The size of BacEMD4 was determined to be 3.5 kDa by Tricine SDS-PAGE. The N-terminal amino acid sequence was similar with that of Subtilosin A. Nucleotide sequencing of the cloned gene confirmed that BacEMD4 was Subtilosin A. BacEMD4 showed bactericidal activity against B. cereus ATCC14579.

A Facile Removal of P-Methoxybenzyl and Diphenylmethyl Ester with Iodotrimethyl-Silane-Triphenylphosphine

Abstract Diphenylmethyl (DPM) and p-methoxybenzyl (PMB) ester of cephalosporin derivatives were converted to the corresponding carboxylic acid using iodotrimethylsilane (TMSI)-triphenylphosphine (TPP) in dichloromethane at room temperature in good yields.

An Effective and Convenient Esterefication of Cephalospor in Derivatives by Using Quarternary Ammonium Salts as Catalysts

Abstract A method for preparing cephalosporin derivatives by reacting cephalosporin alkaline metal salts with organic halide in the presence of quarternary ammonium salts catalyst is disclosed. Δ3 to Δ2 isomerization, a side reaction commonly reported in preparation of cephalosporin derivatives, was successfully eliminated. The desired Δ3 was obtained as a sole product in the reaction.

Diethyl Chlorophosphate: An Effective and Convenient Coupling Reagent of Cephalosporin Derivatives

Abstract A coupling reagent, diethyl chlorophosphate (DECP) 2, was reacted with 2-(2-amino-4-thiazolyl)-2-syn-alkoxyiminoacetic acid 1 to give an active ester intermediate 3.

Identifying the major intermediate species by combining time-resolved X-ray solution scattering and X-ray absorption spectroscopy

Identifying the intermediate species along a reaction pathway is a first step towards a complete understanding of the reaction mechanism, but often this task is not trivial. There has been a strong on-going debate: which of the three intermediates, the CHI2 radical, the CHI2-I isomer, and the CHI2(+) ion, is the dominant intermediate species formed in the photolysis of iodoform (CHI3)? Herein, by combining time-resolved X-ray liquidography (TRXL) and time-resolved X-ray absorption spectroscopy (TR-XAS), we present strong evidence that the CHI2 radical is dominantly formed from the photolysis of CHI3 in methanol at 267 nm within the available time resolution of the techniques (∼20 ps for TRXL and ∼100 ps for TR-XAS). The TRXL measurement, conducted using the time-slicing scheme, detected no CHI2-I isomer within our signal-to-noise ratio, indicating that, if formed, the CHI2-I isomer must be a minor intermediate. The TR-XAS transient spectra measured at the iodine L1 and L3 edges support the same conclusion. The present work demonstrates that the application of these two complementary time-resolved X-ray methods to the same system can provide a detailed understanding of the reaction mechanism.

Improvement of Fibrinolytic Activity of Bacillus subtilis 168 by Integration of a Fibrinolytic Gene into the Chromosome.

Fibrinolytic enzyme genes (aprE2, aprE176, and aprE179) were introduced into the Bacillus subtilis 168 chromosome without any antibiotic resistance gene. An integration vector, pDG1662, was used to deliver the genes into the amyE site of B. subtilis 168. Integrants, SJ3-5nc, SJ176nc, and SJ179nc, were obtained after two successive homologous recombinations. The integration of each fibrinolytic gene into the middle of the amyE site was confirmed by phenotypes (Amy(-), Spec(S)) and colony PCR results for these strains. The fibrinolytic activities of the integrants were higher than that of B. subtilis 168 by at least 3.2-fold when grown in LB broth. Cheonggukjang was prepared by inoculating each of B. subtilis 168, SJ3-5nc, SJ176nc, and SJ179nc, and the fibrinolytic activity of cheonggukjang was 4.6 ± 0.7, 10.8 ± 0.9, 7.0 ± 0.6, and 8.0 ± 0.2 (U/g of cheonggukjang), respectively at 72 h. These results showed that construction of B. subtilis strains with enhanced fibrinolytic activities is possible by integration of a strong fibrinolytic gene via a marker-free manner.

Analysis of Environmental Condition Effects of Waste Landfill on Geomembrane Performance

The effects of acidic and alkaline solutions to be considered waste on the chemical resistance of high density polyethylene (HDPE) geomembranes (GMs) were evaluated. Damaged and intact smooth/textured specimens were immersed in acidic, alkaline and distilled water (pH=4, 12, 8 and 7), and incubated at 20, 40, 60 and 80 °C respectively. Tensile stress of specimens was periodically determined by constant rate of load tensile testing apparatus while polymer structure was examined by a scanning electro-microscope. Damaged HDPE GMs showed excellent acidity-resistance as intact HDPE GMs. High temperature imparted flexibility in HDPE GMs which in turn showed lower tensile strength.