• Korean Journal of Microbiology
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• v.37 no.4
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• pp.245-252
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• 2001

Erm proteins, MLS (macrolide-lincosamide-streptogramin B) resistance factor proteins, show high degree of amino acid sequence homology and comprise of a group of structurally homologous N-methyltransferases. On the basis of the recently determined structures of ErmC` and ErmAM, ErmSF was divided into two domains, N-terminal end catalytic domain and C-terminal end substrate binding domain and attempted to overexpress catalytic domain in E. coli using various pET expression systems. Three DNA fragments were used to express the catalytic domain: DNA fragment 1 encoding Met 1 through Glu 186, DNA fragment 2 encoding Arg 60 to Glu 186 and DNA fragment 3 encoding Arg 60 through Arg 240. Among the pET expression vectors used, pET 19b successfully expressed the DNA fragment 3 and pET23b succeeded in expression of DNA fragment 1 and 2. But the overexpressed catalytic domains existed as inclusion body, a insoluble aggregate. To assist the soluble expression of ErmSF catalytic domains, Coexpression of chaperone GroESL or Thioredoxin and lowering the incubation temperature to $22^{\circ}C$ were attempted, as did in the soluble expression of the whole ErmSF protein. Both strategies did not seem to be helpful. Solubilization with guanidine-HCl and renaturation with gradual removal of denaturant and partial digestion of overexpressed whole ErmSF protein (expressed to the level of 126 mg/ι culture as a soluble protein) with proteinase K, nonspecific proteinase are under way.

• Korean Journal of Crystallography
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• v.4 no.2
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• pp.74-85
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• 1993

Single crystals of LiNbO3 have found extensive application in electro-optic and nonlinear optic devices. However, laser-induced refartive index inhomogeneities, which have been labeled opical damage impose limits on device optical damage in LiNbO3 is imporved if more than 4.5 rml% MgO is added to the melt The laser damage thrueshold increased as much as 100 times better then that of undoped crystals. The MgO doped cystal has thus been urterlsiv81y studied since then. In the study, Mgo:LiNbOs(MLA) single crystals dopsd with 0, 2.5, 5.0, 7.5, 10.0 mol% MgO have been grown by the czocrualski technique. The metls were prepared in the platinum crluible and 15∼20mm diameter crystals were grown with a length of 20∼30mm in a resitance heater. The growth rate was 2.5mm/hr, the rotation speed 15rpn. Before sawing MLN single crystals were annealed for 24 hours under atmosphere at a temperature of 1080℃. After sawing, we have found an annual ring cross section of MNA crystals only in the direction of perpendicilar to the c-axis. Nonuniform dispusion of MgO was pointed out that the cuties of the state of oxide were strongly affected by oxygen partial pressure in.

• Applied Chemistry for Engineering
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• v.33 no.5
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• pp.496-501
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• 2022

In this study, an anode material for lithium secondary batteries was manufactured using petroleum-based residual oil, which is a petroleum refining by-product. Among petroleum-based residual oils, pyrolysis fuel oil (PFO), fluidized catalyst cracking-decant oil (FCC-DO), and vacuum residue (VR) were used as carbon precursors. The physicochemical characteristics of petroleum-based residual oil were confirmed through Matrix-assisted laser desorption/ionization Time-of-Flight (MALDI-TOF) and elemental analysis (EA), and the structural characteristics of anode materials manufactured from residual oil were evaluated using X-ray crystallography (XRD) and Raman spectroscopic techniques. VR was found to contain a wide range of molecular weight distributions and large amounts of impurities compared to PFO and FCC-DO, and PFO and FCC-DO exhibited almost similar physicochemical characteristics. From the XRD analysis results, carbonized PFO and FCC-DO showed similar d₀₀₂ values. However, it was confirmed that FCC-DO had a more developed layered structure than PFO in Lc (Length of a and c axes in the crystal system) and La values. In addition, FCC-DO showed the best cycle characteristics in electrochemical characteristics evaluation. According to the physicochemical and electrochemical results of the petroleum-based residual oil, FCC-DO is a better carbon precursor for a lithium secondary battery than PFO and VR.

• Economic and Environmental Geology
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• v.51 no.4
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• pp.345-358
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• 2018

In this study, we have performed electron probe micro analyzer (EPMA), X-ray differaction (XRD), inductively coupled plasma spectroscopy (ICP), Fourier transform Raman spectroscopy (FT-Raman), far-infrared (FIR), nuclear magnetic resonance (NMR), and pH-DO Analyses for characterizing medicinal mineralogy aspect of the black tourmaline (Shantung, china), black and pink tourmaline (Minas Geraris, Brazil), black touemaline (Daeyu mine, Korea). In addition, heating effects of the tourmaline sauna as well as the effects of tourmaline powder-added soap on skin troubles have been investigated. It has been revealed that chemical composition of the tourmaline is either high in Fe-, Al-, B-rich types. Ratio of the K-Ca, Na-K, and Fe-B reflects the component change property of solid solution. $CaO/CaO+Na_2O$ and MgO/FeO+MgO ratio show high positive correlation. When tourmaline reacts with distilled water, extended reaction time DO values approximately decrease and it stabilizes at DO = 10. Otherwise, pH values increase until 6 hours and it stabilizes at pH = 8 after 24 hours. Distilled water changes to alkaline when it reacts with tourmaline powder and particles. Tourmaline showed lower absorption spectrum strength and transmittance at short wave, where absorption spectrum wavelength and strength were determined by the content of the composition elements and characteristics of crystallography. Increase of the Fe content has been confirmed to be the cause for the reduction of irradiation. For the chemical composition and spectral property of the tourmaline particle samples, it has been found that Si and Fe contents show positive correlation with Far-Infrared irradiation, while Al and Mg contents show negative correlation. For tourmaline powder, it has been confirmed that $^{17}O-NMR$ FWHM (full width at half maximum) decreases when reacts with distilled water. Tourmaline sauna (approximately $100^{\circ}C$) was found to increase $0.5-1.5^{\circ}C$ of body temperature, average of 12 heartbeat, and 10mg Hg of blood pressure. Tourmaline soap had very good aesthetic effect to skin and was confirmed to have above the average improvements to skin troubles (e.g., allergy or atopy).

• Korean Journal of Crystallography
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• v.15 no.2
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• pp.59-68
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• 2004

Three crystal structures of dehydrated partially $Co^{2+}-exchanged$ zeolite A treated with 0.6 Torr of K at $300^{\circ}C$ (for 12 hrs, 6 hrs, and 2 hrs) vapor have been determined by single-crystal X-ray diffraction techniques in the cubic space group Pm3m at 21(1)$^{\circ}C(a=12.181(1)\;{\AA},\;a=12.184(1)\;{\AA},\;and\;a=12.215(1)\;{\AA})\;respectively)$. Their structures were refined to the final error indices, R(weight) of 0.090 with 10 reflections, 0.091 with 82 reflections, and 0.090 with 80 reflections, respectively, for which $1>\sigma(I)$. In each structure, all four $Co^{2+}$ and four $Na^+$ ions to be reduced by K atoms. The cobalt and sodium atoms produced are no longer found in the zeolite. K species are found at five different crystallographic sites: three $K^+$ ions lie at the planes of 8-rings, filling that position, ca. 11.5 K^+$ ions lie on threefold axes, ca. 4.0 in the large cavity and ca. 4.0 in the sodalite cavity, and ca. 0.5 $K^+$ ion is found near a 4-ring. ca. three $K^0$ atoms are found deep into the large cavity on threefold axes. In these structures, crystallographic results show that cationic tetrahedral $K_4$ (and/or triangular $K_3$) clusters have formed in the sodalites of zeolite A. The $K_4$ and/or $K_3$ clusters coordinate trigonally to three oxygens of a six-oxygen ring. The partially reduced ions of these clusters interact primarily with oxygen atoms of the zeolite structure rather than with each other. ca. 14.5K species are found per unit cell, more than the twelve $K^+$ ions needed to balance the anionic charge of zeolite framework, indicating that sorption of $K^0$ has occurred. The three $K^0$ atoms in the large cavity are closely associated with three out of four $K^+$ ions in the large cavity to form $K_7^{4+}$ clusters. The $K_7^{4+}$ cluster not interacts primarily with framework oxygens.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.1
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• pp.41-50
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• 2022

To study the properties of Sr²⁺ exchange into zeolite A with increasing the molar concentration of Na⁺ in given exchange solution, four single crystals of fully dehydrated Sr²⁺- and Na⁺- exchanged zeolite A were prepared by the bath method using mixed ion-exchange solutions. The Sr(NO₃)₂:NaNO₃ molar rations of the ion exchange solution were 1:1(crystal 1), 1:100(crystal 2), 1:250(crystal 3), and 1:500 (crystal 4), respectively, with a total concentration of 0.05 M. The single-crystals were then vacuum dehydration at 623 K and 1×10^-4 Pa for 2 days. Their single-crystal structures were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group Pm3-m, at 100(1) K, and were then refined to the final error indices of R₁/wR₂=0.047/0.146, 0.048/0.142, 0.036/0.128, and 0.040/0.156 for crystals 1, 2, 3, and 4, respectively. In crystals 1 and 2, the 6 Sr²⁺ ions are found at three different crystallographic sites. In crystal 3, 1 Sr²⁺ and 10 Na⁺ ions are found in large cavity and sodalite unit. In crystal 4, only 12 Na⁺ ions occupy three equipoints. The degree of Sr²⁺ ion-exchange decreased sharply from 100 to 16.7 to 0% as the initial Na⁺ concentration increase and the Sr²⁺ concentration decrease. In addition, the unit cell constant of the zeolite framework decreased with this lower level of Sr²⁺ exchange.