• BMB Reports
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• v.37 no.5
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• pp.597-602
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• 2004

N-terminal His-tagged recombinant $\beta$-1,4-galactosyltransferase from Neisseria meningitidis was expressed and purified to homogeneity by column chromatography using Ni-NTA resin. Mutations were introduced to investigate the roles of, Ser68, His69, Glu88, Asp90, and Tyr156, which are components of a highly conserved region in recombinant $\beta$-1,4 galactosyltransferase. Also, the functions of three other cysteine residues, Cys65, Cys139, and Cys205, were investigated using site-directed mutagenesis to determine the location of the disulfide bond and the role of the sulfhydryl groups. Purified mutant galactosyltransferases, His69Phe, Glu88Gln and Asp90Asn completely shut down wild-type galactosyltransferase activity (1-3%). Also, Ser68Ala showed much lower activity than wild-type galactosyltransferase (19%). However, only the substitution of Tyr156Phe resulted in a slight reduction in galactosyltransferase activity (90%). The enzyme was found to remain active when the cysteine residues at positions 139 and 205 were replaced separately with serine. However, enzyme reactivity was found to be markedly reduced when Cys65 was replaced with serine (27%). These results indicate that conserved amino acids such as Cys65, Ser68, His69, Glu88, and Asp90 may be involved in the binding of substrates or in the catalysis of the galactosyltransferase reaction.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.6
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• pp.489-495
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• 2000

The 185 ribosomal RNA gene (185 rDNA) of the marine alga Porphyra sp. 723 (Bangiales, Rhodophyta) was amplified using the polymerase chain reaction and its sequence was analysed. The Porphyra species was a summer strain collected on rocks in upper intertidal zone at Ikidae, Pusan on 23rd July 1999. The fronds were $1{\~}5 cm$ long, monostromatic, and orbicular or ovate shaped, They had spinulate processes at margin of the frond, Comparison of this 185 rDNA sequence with the other Forphyra species indicates that Porphyra sp. 723 has the same 185 rDNA sequence derived from Porphyra suborbiculata (NCBI access number; AB 013180) except one base pair substitution in 2327 base pairs.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.182-182
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• 2014

Multiferroic materials have attracted much attention due to their own fascinating fundamental physical properties and potential technological applications to magnetic/ferroelectric data storage systems, quantum electromagnets, spintronics, and sensor devices. Among single-phase multiferroic materials, $BiFeO_3$, in particular, has received considerable attention because the enhanced ferromagnetism was found by the Fe-site ion substitution with magnetic ions. The structural, the magnetic and the ferroelectric properties of polycrystalline $BiFe_{1-x}Ni_xO_3$ (x=0, 0.01, 0.02, 0.03 and 0.05), which were prepared by the solid-state reaction and the rapid-sintering method, have been investigated. The x-ray diffraction patterns reveal that all the samples are in single phase and show rhombohedral structure with R3c space group. The magnetic properties are enhanced according to the doping content. The Ni-doped $BiFeO_3$ samples exhibit lossy P-E loop due to the oxygen vacancy. The leakage current density of Ni-doped samples (x=0.01 and 0.02) is increased by four orders of magnitude. On the other hand, the x=0.03 and 0.05 samples show the relative reduction of the leakage current.

• Korean Journal of Materials Research
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• v.26 no.11
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• pp.623-627
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• 2016

$La_{1-x}Ba_xMnO_3$ (x = 0.30, 0.35 and 0.40) samples have been prepared by solid-state reaction method. The X-ray diffraction (XRD) study showed that all the samples crystallized in a rhombohedral structure with an R-3c space group. Variation of the magnetization as a function of the temperature and applied magnetic field was carried out. All the samples revealed ferromagnetic to paramagnetic (FM-PM) phase transition at the Curie temperature $T_C{\sim}342K$. The magnetic entropy change was also studied through examination of the measured magnetic isotherms M(H, T) near $T_C$. The magnetocaloric effect was calculated in terms of the isothermal magnetic entropy change. The maximum entropy change reaches a value of 1.192 J/kgK under a magnetic field change of 2.5T for the $La_{0.6}Ba_{0.4}MnO_3$ composition. The relative cooling power (RCP) is 79.31 J/kg for the same applied magnetic field.

• Textile Coloration and Finishing
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• v.7 no.2
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• pp.32-39
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• 1995

Various grades of hydroxyethyl cellulose (HEC, MS 0.65-3.20) were prepared throngh reaction of the knit-cotton-waste with ethylene oxide(EO). The knit-cotton-waste was composed of 98% of $\alpha$-cellulose and 2% of other components, and the cellulose was highly pure. The molar ratio of EO to knit-cotton-waste and that of NaOH to knit-cotton-waste, and the agitation speed were the important factors determining the molar substitution(MS) during the preparation of HEC. The MS of HEC was remarkably increased with increasing molar ratio of EO' to knit-cotton-waste. When the molar ratio of EO to knit-cotton-waste was 3.5, that of NaOH to knit-cotton-waste was 1.25, and agitation speed was 450rpm, it was possible to prepare HEC of MS 2.5. The structure and crystallinity of HECs prepared were determined by FT-IR and X-ray diffraction.

• Progress in Superconductivity
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• v.1 no.2
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• pp.135-140
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• 2000

Distribution of Pr ions between Y- and Ba-site of the $Y(Ba_{1-Xn}Pr_{Xn})_2Cu_3O_y$ ($0{\leq}Xn{\leq}{0.3}$, Xn : nominal composition) material prepared by the solid state reaction method was studied. Although the samples have narrow superconducting transition, tiny peaks of $Y_2BaCuO_5$ impurity phase are included in the x-ray diffraction patterns suggesting that some of the Pr ions are entered into the Y-site. The distribution of Pr ions between Y- and Ba-site was determined by measuring the mass fraction of YBCO and $Y_2BaCuO_5$ phase for each sample through the Rietveld analysis of the x-ray diffraction data. About 60 % of Pr ions occupy the Y-site regardless of the Pr content. Various superconducting parameters such as the oxygen content and the hole concentration etc. are compared before and after the impurity correction.

• Journal of the Korean Wood Science and Technology
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• v.23 no.2
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• pp.37-46
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• 1995

The substitution of carboxymethylated hydroxyl group in pulp revealed more hydrophilic than hydroxyl group. And then fibers were more flexible, swell more which leads to better conformation between fibers in turn this raise paper strength. In this paper, we tried to chemical modifyings of recycled fiber, OCCs(old corrugated containers). Many researchers have examined chemical modification of papermaking fiber by partial carboxymethylation(PCM) using a organic solvent processes. We made modified PCM processes adapted waters m replace of the organic solvent. Our testings for the optimum conditions on the new method, conditions as reaction time, temperature, liquor ratios were designed likely plant system. Freenesses(SR$^{\circ}$) were increased following on carboxyl content of the samples. Handsheets of untreated samples and partial carboxymethylated OCCs were made by optimum conditions on different concentrations of the reagent. As results, maximum 25% strength increasing effects were obtained by the new method.

• The Korean Journal of Food And Nutrition
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• v.31 no.1
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• pp.195-201
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• 2018

This study was intended to investigate the characteristics of muffins prepared with allulose which is low-calorie and physiologically functional rare sugar. Volume and specific volume of muffins increased significantly with allulose addition, but not with its contents. Muffin heights also increased as allulose was added more. Baking loss rate and moisture contents were not significantly different among samples. Allulose seemed to have nearly same water holding capacity with sucrose. Lightness of muffin crust and crumb both decreased, but redness and yellowness increased according to allulose, the reducing sugar addition by Maillard reaction. In the texture profile analysis, Hardness of AL100 was higher significantly (p<0.05) and springiness, cohesiveness and fracturability increased according to the allulose contents. In the sensory evaluation, AL0 was the sweetest and AL0 and AL25 got higher overall acceptance score. Physical characteristics were not different (p<0.05) among AL0, Al25 and AL50. As a result, 25% sucrose substitution with allulose can provide low-calorie, anti-hyperglycemic and tasty muffin.

• Journal of the Korean Ceramic Society
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• v.31 no.9
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• pp.1037-1043
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• 1994

The effects of annealing atmosphere and temperature on piezoelectricity (k33) and the mechanical strength of machined PZT was studied. Morphotropic Nb-doped PZT was sintered, machined to a rod and then annealed between 80$0^{\circ}C$ and 100$0^{\circ}C$ in air, PbZrO3, and CuO atmospheres respectively. In air or PbZrO3 atmosphere, the compressive strength of Nb-doped PZT increased by 12% with little change in k33 irrespective of annealing temperature. In CuO atmosphere, on the other hand, the compressive strength increased by 20% with little change in k33 at 80$0^{\circ}C$ but both turned to significant decrease above 90$0^{\circ}C$. The examination of the phase distribution and microstructure beneath the surface of CuO-treated PZT revealed that the changes in compressive strength and k33 are closely related to the reaction between PZT and vaporized CuO:liquid PbO precipitated in shallow surface region by the substitution of Cu to Pb sites enhances the decrease in microcracks and the surface roughness at 80$0^{\circ}C$ ; rapid evaporation of precipitated PbO expands a porous region of changed composition into the bulk above 90$0^{\circ}C$.

• Proceedings of the Petrological Society of Korea Conference
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• 2000.05a
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• pp.3-11
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• 2000

The earth environment consists of four spheres : geosphere, hydrosphere, atmosphere and biosphere. The geosphere consists mostly of minerals. It, however, contains some water and air in its shallow depth. Although hydrosphere and atmosphere consist predominantly of water and air, respectively, both contain some minerals. The biosphere consisting of various organisms is present in the interfaces of geosphere, hydrosphere and atmosphere. The natural environment of the earth is continuously changing by the interaction of four spheres. It suggests that out relevant environmental problems can not be revolved without understanding the natural relationship of these four spheres. Minerals in our environment are very important because they are the main constituent materials of the earth and they control our environment. The roles of minerals in our environment have not been understood even in the scientific society. Thus their roles have been neglected. Review of studies on the environmental mineralogy so far made at our laboratory and others show that minerals control the environment in various ways. Minerals neutralize the acid water as well as acid rain. Minerals in soils and rocks are major neutralizer of the acid rain. Salinization of sea water is attributed to the ionic substitution between minerals and sea water. Some minerals control the humidity of the air. Corals, the products of biomineralization, are the main carbon controller of the air. Minerals also adsorb heavy metals, organic pollutants and radioactive nuclides. Such remarkable functions for controlling the environment come from the mineral-water reaction and biomineralization. All these phenomena are subjects of the environmental mineralogy, a new field of earth science.