• Journal of Microbiology and Biotechnology
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• v.9 no.4
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• pp.429-435
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• 1999

An adenosine 5'-monophosphate deaminase (AMP aminohydrolase, EC 3.5.4.6) was purified to homogeneity from the cell-free extract of Saccharomyces cerevisiae DKCTC7248. The molecular mass of subunit was estimated to be 80 kDa on SDS-PAGE, and that of the holoenzyme was shown to be 240 kDa by gel filtration. The isoelectric point of the enzyme (AMP deaminase D) was determined to be 6.2. The AMP deaminase D was specific towards AMP with an apparent $K_m$ value of 4.1 mM and a Hill coefficient, $n_H$, of 2.2. Both ATP and ADP were positive allosteric effectors of the AMP deaminase D: The apparent $K_{m}$ was decreased to 1.6 mM and 3.3 mM in the presence of 0.1 mM ATP and ADP, respectively, lowering $n_{H}$ to 1.0. Univalent cations like $K^+, Na^+ and Li^ +$ activated the enzyme but some divalent cations such as $Cu^{ 2+} and Cd^{2+}$ showed strong inhibitory effects. This enzyme displayed optimum activity at $30^{\circ}C$ and pH 7.0. In addition, it was stable up to $45^{\circ}C$ and over a wide pH range(pH 5.5-9.0). Amino acid sequences of its N-terminal region were analyzed to be ADYKMQMFADDA.

• Polymer(Korea)
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• v.33 no.6
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• pp.555-560
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• 2009

Sulfonic acid of the sulfonated 6FDA-based polyimides were exchanged with the monovalent ($Li^+$, $Na^+$, $K^+$) and divalent ($Mg^{2+}$, $Ca^{2+}$, $Ba^{2+}$) ions. The effect of metal cations exchanged sulfonated polyimides was investigated in terms of gas permeability and selectivity for $CO_2$, $O_2$ and $N_2$ gases. Thermogravimetric analysis showed that thermal stability of sulfonated polyimide was improved by exchanged metal cations. The permeabilities of monovalent cation-exchanged, sulfonated polyimide were reduced as the ion radius reduced [$Li^+$(0.059 nm)>$Na^+$(0.102 nm)>$K^+$(0.138 nm)], and those of divalent cations exchanged were determined by the ionic radii and electrostatic crosslinking between the polymer and metal cations, whereas the selectivities of all the metal cation-exchanged, sulfonated polyimides for $CO_2/N_2$ and $O_2/N_2$, were higher than those of sulfonated polyimide membranes. The sulfonated polyimide exchanged with the potassium cation showed the $O_2$ permeability of 89.98 Barrer [$1\times10^{-10}\;cm^3$(STP) $cm/cm^2{\cdot}s{\cdot}cmHg$] and the sulfonated polyimide exchanged with the lithium cation showed the $O_2/N_2$ selectivity of 12.9.

• Journal of the Mineralogical Society of Korea
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• v.22 no.3
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• pp.249-259
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• 2009

The objective of this research was to find out the physical properties, such as dispersion and coagulation, of soil minerals depending on the types and concentrations of the cations in aqueous solution. Hwangto samples were obtained from 90 to 130 cm from surface at Jangdong-ri, Donggang-Myon, Naju, Chonnam Province. The clay fraction (< $2\;{\mu}m$) was separated by sedimentation method from the bulk soils. Both Hwangto and clay fractions, and the same samples after removal of amorphous and crystalline iron oxides were used in this experiment. The effect of 4 cations ($Na^+$, $K^+$, $Mg^{2+}$, $Ca^{2+}$) and their concentrations on settling speed and basal spacing of the minerals were observed to examine the physical properties of the soil and clay minerals. Hwangto mainly consisted of quartz, and the clay fractions consisted of kaolinite, illite, and vermiculite. The bulk soils contained 16.3 mg/kg of amorphous iron oxides and 436 mg/kg of crystalline iron oxides. Clay fractions were dispersed better than bulk soils due to their smaller particle size than that of the bulk samples in the aqueous solution. The bulk and clay samples were dispersed better when iron oxides were removed because of coating of minerals by the iron oxides. Clay minerals were settled faster as the charge and the concentration of cations added increased. The d-spacing of kaolinite and illite did not change when 4 types of cations were added. The d-spacing of vermiculite showed $14.04\;{\AA}$ when divalent cations were added while that of vermiculite showed $13.9\;{\AA}$ when monovalent cations were added. It may be attributed to the hydration radii of cations. This study indicated that both coating of iron oxides on minerals and types and concentrations of cations affect dispersion of minerals in solution and d-spacing of expanding clay minerals such as vermiculite.

• Archives of Pharmacal Research
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• v.21 no.6
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• pp.692-697
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• 1998

GTP cyclohydrolase I catalyzing the first reaction in the biosynthesis of pterin moiety of folic acid in bacteria, was purified from Streptomyces tubercidicus by at least 203-fold with a yield of 32% to apparent homogeneity, using ammonium sulfate fractionation, DEAE-cellulose, Sepharose CL-6B, and hydroxylapatite column chromatography. The molecular weight of the native enzyme was estimated to be 230,000 daltons by gel permeation chromatography. The purified enzyme gave a single band on sodium dodesyl sulfate-polyacrylamide gel electrophoresis and its molecular weight was apparently 58,000 daltons. These results indicate that the enzyme consists of four subunits with the same molecular weight. The $K_m$ and $V_{max}$ values for GTP of the purified enzyme were determined to be 80${\mu}$M and 90nmol/min (mg protein), respectively. The optimum pH and temperature for the enzyme reaction were pH 7.5-8.5 and $40-42^{\circ}C$, respectively. Coenzyme or metal ion was not required for the enzyme activity. The enzyme activity was inhibited by most divalent cations, while it was slightly activated by potassium ion. In case of nucleotides, CTP, GMP, GDP, and UTP inhibited enzyme activity, among which GDP exhibited the strongest inhibitory effect.

• Journal of the Korean Ceramic Society
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• v.29 no.11
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• pp.900-904
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• 1992

High temperature electrical conductivity was measured for perovskite La0.98Sr0.02MnO3 at 200~130$0^{\circ}C$ as a function of Po2 and 1/T. Perovskite La1-xSrxMnO3 system is the typical oxygen electrode in solid oxide fuel cell (SOFC). Acetate precursors were used for the preparation of mixed water solution and the calcined powders were reacted with Na2CO3 flux in order to obtain highly reactive powders of perovskite La0.98Sr0.02MnO3. The relative density was greatly increased above 90% because of the homogeneous sintering. From the conductivity ($\sigma$)-temperature and conductivity-Po2 at constant temperature, the defect structure of La0.98Sr0.02MnO3 was discussed. From the slope of 1n($\sigma$) vs 1/T, the activation energy of 0.069 and 0.108eV were evaluated for above 40$0^{\circ}C$, respectively. From the relationship between $\sigma$ and Po2, it was found that the decomposition of La0.98Sr0.02MnO3 was occurred at 10-15.5 atm(97$0^{\circ}C$) and 10-11 atm(125$0^{\circ}C$). It is supposed that the improvement of p-type conductivity may be leaded by the increase of Mn4+ concentration through the substitution of divalent/monovalent cations for La site in LaMnO3.

• BMB Reports
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• v.32 no.2
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• pp.161-167
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• 1999

The role of oxidative stress in the initiation and the complication of diabetes was examined by monitoring blood glucose increase and oxidative DNA damage in rats treated with alloxan or streptozotocin (STZ). Oxidative DNA damage was assessed by quantitating 8-oxo-2'-deoxyguanosine ($oxo^8dG)$ excreted in urine and the $oxo^8dG$ accumulated in pancreas DNA. Both alloxan and STZ treatments resulted in an abrupt increase in blood glucose and significant increases in urinary and pancreatic $oxo^8dG$. Pretreatment of buthionine sulfoximine (BSO), a glutathione-depleting agent, slightly potentiated the increase of blood glucose and urinary $oxo^8dG$ in the alloxan- and STZ-treated rats. Furthermore, the BSO pretreatment caused significant amplification of pancreatic $oxo^8dG$ increase in the rats. On the other hand, pretreatment with 1,10- phenanthroline (o-phen), a chelator of divalent cations, showed different results between alloxan- and STZ-treated rats. The o-phen pretreatment completely blocked diabetes and the increase of $oxo^8dG$ by alloxan treatment, while it potentiated the increase of blood glucose and $oxo^8dG$ by STZ treatment. The results demonstrate that the causative effect of alloxan on diabetes may be the generation of reactive oxygen species through a Fenton type reaction, but that of STZ may not.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.5
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• pp.734-740
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• 2010

Overuse of veterinary antibiotics threats public health and surrounding environment due to the occurrence of antibiotic resistant bacteria. The objective of this study was to evaluate the antibiotic's concentrations of tetracycline (TC), chlortetracycline (CTC), and oxytetracycline (OTC) in a tetracycline group (TCs), sulfamethazine (SMT), sulfamethoxazole (SMX), and sulfathiazole (STZ) in a sulfonamide group, lasalocid (LSL), monensin (MNS), and salinomycin (SLM) in a ionophore (IPs), and tylosin (TYL) in a macrolide (MLs) group from soil, water, and sediment samples adjacent to a cattle manure composting facility. For all samples of soil, water, and sediment, the highest concentrations were detected in TCs among the tested antibiotics because of its higher annual consumption in veterinary farms, Korea and its higher cohesiveness with divalent or trivalent cations in soil. Moreover, the concentrations of residual antibiotics in September were generally higher than in June because of heavier rainfall in June. We suggest that continual monitoring and developing guideline of antibiotics are needed to control residual antibiotics in the environment.

• Journal of the Mineralogical Society of Korea
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• v.10 no.2
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• pp.105-113
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• 1997

Mineral description and mineralogical characterization were made for the wellsite, a barrian zeolite, which found as diagenetic alterations in the Miocene pyroclastic rocks in Gampo area. The wellsite occurs together with clinoptilolite, smectite and apatite as euhedral crystallites (0.2~0.4mm) forming interpenetraion twinning in the vesicles of altered pmice fragments. Compared to other reported wellsites, the wellsite is rather silicic (Si/(Al+Fe): 3.12-3.16) and Ca-rich. Unit cell dimensions and chemical formular determined from XRD, EMPA and TGA data are as follows:a=9.883$\AA$, b=14.204$\AA$, c=8.677$\AA$, $\beta$-124.764$^{\circ}$, (Ba0.57K0.36)(Ca1.18Na0.04)Al3.9Si12.1O32.13.9H2O.The cation composition of the Gampo wellsite, which shows an exchange reaction in the form of Ba2++Ca2+=2(K++Na-), is deviated far from the compositional range of a phillipsite-harmotome series. Due to higher abundance of divalent cations (Ca, Ba) and si in the wellsite, cimpared to those of the phillipsite and harmotome reported in other areas, the zeolite seems to be characteristic of higher water content (18.7 wt%) and higher thermal stability. XRD, chemical and thermo-chemical results of the wellsite reflects that wellsite is rather a Ba- and Ca-rich end member of a phillipsite-harmotome-wellsite series than an intermediate phase of phillipsite-harmotome series or a barrian variety of phillipste.

• Journal of Applied Biological Chemistry
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• v.42 no.1
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• pp.12-18
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• 1999

Sucrose synthase (EC 2.4.1.13) has been purified from the plant cytosolic fraction of chickpea (Cicer arietinum L. cv. Amethyst) nodules. The native enzyme had a molecular mass of $356{\pm}15kD$. The subunit molecular mass was $87{\pm}2kD$, and a tetrameric structure is proposed for sucrose synthase of chickpea nodule. Optimum activities in the sucrose cleavage and synthesis directions were at pH 6.5 and 9.0, respectively. The purified enzyme displayed typical hyperbolic kinetics with substrates in cleavage and synthesis reactions. Chickpea nodules sucrose synthase had a high affinity for UDP ($K_m$, $8.0{\mu}M$) and relatively low affinities for ADP ($K_m$, 0.23 mM), CDP ($K_m$, 0.87 mM), and GDP ($K_m$, 1.51 mM). The $K_m$ for sucrose was 29.4 mM. In the synthesis reaction, UDP-glucose ($K_m$, $24.1{\mu}M$) was a more effective glucosyl donor than ADP-glucose ($K_m$, 2.7 mM), and the $K_m$ for fructose was 5.4 mM. Divalent cations, such as $Ca^{2+}$, $Mg^{2+}$, and $Mn^{2+}$, stimulated the enzyme activity in both the cleavage and synthesis directions, and the enzyme was very sensitive to inhibition by $HgCl_2$ and $CuSO_4$.

• Journal of Applied Biological Chemistry
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• v.55 no.4
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• pp.241-246
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• 2012

Veterinary antibiotics can enter the soil ecosystem and then may be transported into groundwater via leaching process. The main aim of this study is to investigate the distribution and mobility of tetracycline, amoxicillin and sulfathiazole in soil. The adsorption of veterinary antibiotics were applied to the Freundlich adsorption isotherms. Adsorption coefficient ($K_F$) was indicated oxytetracycline > amoxicillin > sulfathiazole. Oxytetracycline concentration was highly detected in soil than in leachate. It is assumed that oxytetracycline was strongly absorbed by divalent cations such as $Ca^{2+}$ in soil. However, amoxicillin and sulfathiazole were shown higher mobility due to the lower distribution coefficient.