• Journal of the Korean Chemical Society
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• v.45 no.6
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• pp.577-588
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• 2001

Eu doped YRO$_4$ (R=As, Nb, P, V) red phosphors were prepared by the combinatorial chemistry method. The quaternary material library of tetrahedron-type composition array was designed to investigate the luminescence of the host material under UV and VUV excitations (254, 147 nm). The photoluminescent characteristics of the samples were comparable to the commercially available red phosphors such as (Y, Gd)BO$_3$: $Eu^{3+}$ and Y$_2$O$_3$: In view of the luminescence yield, V rich region was found to be optimum under UV excitation. But the results under VUV excitation were different from those of UV excitation, the samples of the composition containing a large amount of P shows the highest luminescence. Especially, higher luminescence was obtained in $Y_{0.9}$(A$S_{0.06}$N$B_{0.06}P_{0.83}V_{0.06}$) O$_4$: $Eu_{0.1}$ phosphors than commercial (Y, Gd)BO$_3$red phosphors under 147 nm excitation.

• The Korean Journal of Pesticide Science
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• v.10 no.2
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• pp.149-152
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• 2006

Construction of focused library of 2-benzylimino-1,3-thiazolines 7 through molecular modification of 3-alkyl-2-phenylimino-1,3-thiazolines 1 which showed selective fungicidal activity against rice blast and their fungitoxic activity against 6 kinds of typical plant diseases was described. Fifty four compounds of focused library of 2-benzylimino-1,3-thiazolines 7 were synthesized from the reaction of the corresponding $\gamma$-chloroacetoacetanilides 6 with N-benzyl thioureas 5 by parallel synthetic methodology. As results of fungicidal screening against the typical plant diseases, twenty eight kinds of 7 at 100 ${\mu}g$ $mL^{-1}$ showed the control value over 50% against tomato late blight.

• Journal of Microbiology and Biotechnology
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• v.13 no.5
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• pp.823-827
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• 2003

Streptomyces venezuelae ATCC 15439 is notable in its ability to produce two distinct groups of macrolactones. It has been reported that the generation of two macrolactone structures results from alternative expression of pikromycin (Pik) polyketide synthase (PKS). It was previously reported that the hybrid pikromycin-tylosin PKS can also produce two different macrolactones but its mechanistic basis remains unclear. In order to address this question, a series of site-directed mutagenesis of tentative alternative ribosome binding site and translation start codons in tylGV were performed. The results suggest that macrolactone ring size is not determined by the alternative expression of TylGV but through other mechanism(s) involving direct interaction between the PikAIII and TE domain or skipping of the final chain elongation step. This provides new insight into the mechanism of macrolactone ring size determination in hybrid PKS as well as an opportunity to develop novel termination activities for combinatorial biosynthesis.

• The Plant Pathology Journal
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• v.31 no.1
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• pp.1-11
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• 2015

Antimicrobial cyclic peptides derived from microbes bind stably with target sites, have a tolerance to hydrolysis by proteases, and a favorable degradability under field conditions, which make them an attractive proposition for use as agricultural fungicides. Antimicrobial cyclic peptides are classified according to the types of bonds within the ring structure; homodetic, heterodetic, and complex cyclic peptides, which in turn reflect diverse physicochemical features. Most antimicrobial cyclic peptides affect the integrity of the cell envelope. This is achieved through direct interaction with the cell membrane or disturbance of the cell wall and membrane component biosynthesis such as chitin, glucan, and sphingolipid. These are specific and selective targets providing reliable activity and safety for non-target organisms. Synthetic cyclic peptides produced through combinatorial chemistry offer an alternative approach to develop antimicrobials for agricultural uses. Those synthesized so far have been studied for antibacterial activity, however, the recent advancements in powerful technologies now promise to provide novel antimicrobial cyclic peptides that are yet to be discovered from natural resources.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.10a
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• pp.21-21
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• 2018

Natural product substances have historically served as the most significant also be prepared by source of new leads for pharmaceutical development. They can chemical synthesis(both semisynthesis and total synthesis) and have played a important role in the field of organic chemistry by providing synthetic targets. Rcently, they have also been extended for commercial purpose to refer to medicinal products, health functional foods, dietary supplements and cosmetics from natural sources. A large number of currently prescribed drugs have been either directly derived from or inspired by natural products. However, with the advent of robotics, bioinformatics, high throughput screening(HTS), molecular biology-biotechnology, combinatorial chemistry, in silico(molecular modeling) and other methodologies, the pharmaceutical industry has largely moved away from plant derived natural products as a source for leads and prospective drug candidates. The strategy for natural prduct industry is now changing from drug approaches to health foods by identifying effective natural products as preparations. In Korea, a lot of development of natural product based drugs have been done, but very few on health functional foods. The concept of natural product based health foods is not active components as lead compounds but standardized extracts or preparation mixed with other medicinal plants. The representative material has been recently known to be a standardized ginseng extract "Ginsana G 115" developed by Swiss Pharmaton company. The purpose of this presentation is to underline how natural products research continues to make significant contributions in the domain of discovery and development of new health functional foods. It is proposed to present the development of high value added health food or health functional foods through scientific investigation on efficacy and standardization of new materials form natural products.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.842-851
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• 2011

A multi-cell test system with 25 independent cells is used to test different electrode materials simultaneously for polymer electrolyte membrane fuel cells (PEMFCs). Twenty-five segmented membrane electrode assemblies (MEAs) having the same or different Pt-loading are prepared to analyze the performance deviation of cells in the multi-cell test system. Improvements in the multi-cell test system are made by ensuring that the system performs voltage sensing for the cells individually and inserting optimum gaskets between the MEAs and the graphite plates. The cell performances are improved and their deviations are significantly decreased by these modifications. The performance deviations changed according to various cell configurations because the operating conditions of the cells, such as the gas flow and concentration, differed. This cell system can be used to test multiple electrodes simultaneously because it shows relatively uniform performance under the same conditions as well as linear correlation with various catalyst loadings.

• Journal of the Korean Chemical Society
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• v.46 no.4
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• pp.336-345
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• 2002

In this study, we have screened $Eu^{3+}$- and $Tb^{3+}$-activated candidate phosphors for PDP in the sys-tems of CaO-Gd$_2$O$_3$-Al$_2$O$_3$ by combinatorial chemistry and investigated the synthetic temperature, optimum com-position and luminescent properties about the candidate phosphors. To construct the emission intensity library by VUV PL, we have synthesized 210 different compositional samples using a polymerized-complex method. Good luminescent samples were identified by X-ray diffraction method. $Ca_$\alpha$$G$d_{0.95-$\alpha$-$\beta$}Al_$\beta$O_$\delta$$ : Eu(0.02< $\alpha$+$\beta$ <0.04) phos-phors screened as a red phosphor have good color purity than commercial phosphor. In the candidate phosphors of CaGdAl$_3O_7$ : Tb, Ca$Al_{12}O_{19}$ : Tb, Gd$_4$Al$_2O_9$ : Tb, and Gd$_3Al_5O_{12}$ : Tb CaGdAl$_3O_7$ : Tb, and Ca$Al_{12}O_{19}$ : Tb have shorter decay time than commercial phosphor.

• Journal of Pharmaceutical Investigation
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• v.30 no.3
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• pp.191-199
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• 2000

Genomics is providing targets faster than we can validate them and combinatorial chemistry is providing new chemical entities faster than we can screen them. Historically, the drug discovery cascade has been established as a sequential process initiated with a potency screening against a selected biological target. In this sequential process, pharmacokinetics was often regarded as a low-throughput activity. Typically, limited pharmacokinetics studies would be conducted prior to acceptance of a compound for safety evaluation and, as a result, compounds often failed to reach a clinical testing due to unfavorable pharmacokinetic characteristics. A new paradigm in drug discovery has emerged in which the entire sample collection is rapidly screened using robotized high-throughput assays at the outset of the program. Higher-throughput pharmacokinetics (HTPK) is being achieved through introduction of new techniques, including automation for sample preparation and new experimental approaches. A number of in vitro and in vivo methods are being developed for the HTPK. In vitro studies, in which many cell lines are used to screen absorption and metabolism, are generally faster than in vivo screening, and, in this sense, in vitro screening is often considered as a real HTPK. Despite the elegance of the in vitro models, however, in vivo screenings are always essential for the final confirmation. Among these in vivo methods, cassette dosing technique, is believed the methods that is applicable in the screening of pharmacokinetics of many compounds at a time. The widespread use of liquid chromatography (LC) interfaced to mass spectrometry (MS) or tandem mass spectrometry (MS/MS) allowed the feasibility of the cassette dosing technique. Another approach to increase the throughput of in vivo screening of pharmacokinetics is to reduce the number of sample analysis. Two common approaches are used for this purpose. First, samples from identical study designs but that contain different drug candidate can be pooled to produce single set of samples, thus, reducing sample to be analyzed. Second, for a single test compound, serial plasma samples can be pooled to produce a single composite sample for analysis. In this review, we validated the issue whether the second method can be applied to practical screening of in vivo pharmacokinetics using data from seven of our previous bioequivalence studies. For a given drug, equally spaced serial plasma samples were pooled to achieve a 'Pooled Concentration' for the drug. An area under the plasma drug concentration-time curve (AUC) was then calculated theoretically using the pooled concentration and the predicted AUC value was statistically compared with the traditionally calculated AUC value. The comparison revealed that the sample pooling method generated reasonably accurate AUC values when compared with those obtained by the traditional approach. It is especially noteworthy that the accuracy was obtained by the analysis of only one sample instead of analyses of a number of samples that necessitates a significant man-power and time. Thus, we propose the sample pooling method as an alternative to in vivo pharmacokinetic approach in the selection potential lead(s) from combinatorial libraries.

• Archives of Pharmacal Research
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• v.25 no.6
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• pp.801-806
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• 2002

Cyclicpeptides are important targets in peptide synthesis because of their interesting biological properties. Constraining highly flexible linear peptides by cyclization is one of the mostly widely used approaches to define the bioactive conformation of peptides. Cyclic peptides often have increased receptor affinity and metabolic stability over their linear counterparts. We carried out virtual screening experiment via docking in order to understand the interaction between HLE-Human Leukocyte Elastase and ligand peptide and to identify the sequence that can be a target in various ligand peptides. We made cyclic peptides as a target base on Metlle-Phe sequence having affinity for ligand and receptor active site docking. There are three ways to cyclize certain sequences of amino acids such as Met-lie-Phe-Gly-Ile. First is head-to-tail cyclization method, linking between N-terminal and C-terminal. Second method utilizes amino acid side chain such as thiol functional group in Cys, making a thioether bond. The last one includes an application of resin-substituted amino acids in solid phase reaction. Among the three methods, solid phase reaction showed the greatest yield. Macrocyclization of Fmoc-Met-Ile-Phe-Gly-Ile-OBn after cleavage of Fmoc protection in solution phase was carried out to give macrocyclic compound 5 in about 7% yield. In the contrast with solution phase reaction, solid phase reaction for macrocyclization of Met-Ile-Phe-Gly-Ile-Asp-Tentagel in normal concentrated condition gave macrocyclic compound 7 in more than 35% yield.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.277.2-277.2
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• 2013

Petri dishes and glass slides have been widely used as general substrates for in vitro mammalian cell cultures due to their culture viability, optical transparency, experimental convenience, and relatively low cost. Despite the aforementioned benefit, however, the flat two-dimensional substrates exhibit limited capability in terms of realistically mimicking cellular polarization, intercellular interaction, and differentiation in the non-physiological culture environment. Here, we report a protocol of culturing embryonic rat hippocampal neurons on the electro-spun polymeric network and the results from examination of neuronal cell behavior and network formation on this culture platform. A combinatorial method of laser-scanning confocal fluorescence microscopy and live-cell imaging technique was employed to track axonal outgrowth and synaptic connectivity of the neuronal cells deposited on this model culture environment. The present microfiber-based scaffold supports the prolonged viability of three-dimensionally-formed neuronal networks and their microscopic geometric parameters (i.e., microfiber diameter) strongly influence the axonal outgrowth and synaptic connection pattern. These results implies that electro-spun fiber scaffolds with fine control over surface chemistry and nano/microscopic geometry may be used as an economic and general platform for three-dimensional mammalian culture systems, particularly, neuronal lineage and other network forming cell lines.