• Korean Journal of Medicinal Crop Science
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• v.14 no.6
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• pp.367-370
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• 2006

The study was carried out to establish an improved protocol for shoot organogenesis and plant regeneration from leaf explant cultures of Scrophularia buergeriana M. with the treatment of ethylene inhibitors [silver nitrate (AgNO$_3$), aminoethox-yvinylglycine (AVG), Cobalt chloride (CoCl$_2$)]. The regenerated shoots obtained from leaf explant cultures on MS medium containing 2 mg/l BAP, The additions of AgNO$_3$. AVG and CoC1$_2$ substantially improved the shoot regeneration frequency, at the optimal concentration of 7 mg/L, 7 mg/L, and 3 mg/L respectively, The regenerated shoots could be easily rooted with 0.1 mg/L IBA treatment. The noted plants were hardened and transferred to vermiculite with a 85% survival rate where they grew normally.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1277-1281
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• 2011

Making use of chitosan (CS) and ethylenediaminetetraacetic acid (EDTA) as a reaction system, CS-EDTA nanoparticles were synthesized through a facile counterion complex coacervation method. $Ag^+$ could enter porous CS nanoparticles synthesized with this method, allowing Ag nanoparticles within chitosan nanoparticles were synthesized by reducing silver nitrate with chitosan. Because of the noncovalent interaction between CS and EDTA, the EDTA could be easily removed via dialysis against water, and pure core/shell-type Ag/CS nanoparticles could be obtained. The nanoparticles showed higher antibacterial activity toward E. coli than the active precursor Ag nanoparticles and CS.

• Journal of Microbiology and Biotechnology
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• v.10 no.1
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• pp.35-42
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• 2000

Reaction characteristics of 4-methylcatechol 2,3-dioxygenase (4MC230) purified from Pseudomonas putida SU10 with a higher activity toward 4-methylcatechol than catechol or 3-cethylcatechol were studied by altering their physical and chemical properties. The enzyme exhibited a maximum activity at pH 7.5 and approximately 40% at pH 6.0 for 4-methylcatechol hydrolysis. The optimum temperature for the enzyme was around $35^{\circ}C$, since the enzyme was unstable at higher temperature. Acetone(10%) stabilized the 4MC230. The effects of solvent and other chemicals (inactivator or reactivator) for the reactivation of the 4MC230 were also investigated. Silver nitrate and hydrogen peroxid severely deactivated the enzyme and the deactivation by hydrogen peroxide severely deactivated the enzyme and the deactivation by hydrogen peroxide was mainly due to the oxidation of ferrous ion to ferric ion. Some solvents acted as an activator and protector for the enzyme from deactivation by hydrogen peroxide. Ascorbate, cysteine, or ferrous ion reactivated the deactivated enzyme by hydrogen peroxide. The addition of ferrous ion together with a reducing agent fully recovered the enzyme activity and increased its activity abut 2 times.

• Animal Systematics, Evolution and Diversity
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• v.26 no.1
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• pp.21-27
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• 2010

Two marine euplotid ciliates, i.e. Euplotes cristatus Kahl, 1932 and E. minuta Yocom, 1930, were collected from the public waterfront of Incheon on the Yellow Sea and from the Songjeong Beach, Busan, in the Strait of Korea, respectively. These two species were verified as unrecorded species in Korea. These species were described based on live observation, protargol impregnation, and silver nitrate impregnation. In addition, the small subunit ribosomal DNA (SSU rDNA) sequences of the two species were compared with previously known sequences of the Euplotes species. Euplotes cristatus has an elongated oval form, size in vivo of $60-84{\times}38-68\;{\mu}m$, 35-50 adoral zone of membranelles (AZM), 10 frontoventral cirri (FVC), 5 transverse cirri (TC), 4-5 caudal cirri (CC), 8 dorsal kineties (DK), 10-16 dorsal cilia of middle DK, and silverline system of single-vannus type. Euplotes minuta has a small ovoid form ($44-53{\times}26-35\;{\mu}m$ in vivo), 31-41 AZM, 10 FVC, 5 TC, 4 CC, 9 DK, 10-12 dorsal cilia of middle DK, and silverline system of single-vannus type.

• Bulletin of the Korean Chemical Society
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• v.32 no.8
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• pp.2607-2610
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• 2011

Monodispersed Ag/$TiO_2$ core/shell nanoparticles were synthesized in solution via colloid-seeded deposition process using Ag nanoparticles as colloid seeds and $Ti(SO_4)_2$ as Ti-source respectively. Silver nitrate was reduced to Ag nanoparticles with $N_2H_4{\cdot}H_2O$ in the presence of CTAB as stabilizing agent. The titania sols hydrolyzed by the $Ti(SO_4)_2$ solution deposited on the surface of Ag nanoparticles to form the Ag/$TiO_2$ core/shell nanoparticles. Inductively coupled plasma atomic emission spectrometry (ICP-AES) showed low amount of Ag ion leaching from the Ag/$TiO_2$ core/shell nanoparticles. The Ag/$TiO_2$ core/shell nanoparticles indicated excellent antibacterial effects against Escherichia coli and maintained long-term antibacterial property.

• Journal of Plant Biotechnology
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• v.36 no.1
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• pp.81-86
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• 2009

An efficient and reproducible plant regeneration system was established using transverse thin cell layers (tTCLs) in five cultivars of Brassjca juncea L. The effects of medium conditions, explant types (tTCLs of hypcotyl and cotyledonary petiole) on shoot regeneration were examined in this study. The maximum shoot regeneration frequency was obtained in Murashige and Skoog (MS) medium supplemented with 4 mg/L 6-benzylaminopurine (BA) and 0.2 mg/L 1-naphthaleneacetic acid (NAA). The hypocotyls derived tTCL explants had more shoot regeneration frequency (52%) than the cotyledonary petiole derived tTCL explants. Shoot induction was further improved by the addition of silver nitrate ($AgNO_3$) in the regeneration medium. A significant genotypic effect was also observed between the five cultivars; Rai-5 displayed higher capacities to produce shoots than other cultivars. Regenerated shoots were rooted on MS basal medium without PGRs which induced 90% of roots. The plantlets established in greenhouse conditions with 99% survival, flowered normally and set seeds. The regenerated plants were fertile and identical to source plants.

• BMB Reports
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• v.29 no.4
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• pp.321-326
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• 1996

Spinach glycolate oxidase was subjected to a series of chemical modifications aimed at identifying amino acid residues essential for catalytic activity. The oxidase was reversibly inactivated by treatment with pyridoxal 5'-phosphate (PLP). The inactivation by PLP was accompanied by the appearance of an absorption peak of around 430 nm, which was shifted to 325 nm upon reduction with $NaBH_4$. After reduction, the PLP-treated oxidase showed a fluorescence spectrum with a maximum of around 395 nm by exciting at 325 nm. The substrate-competitive inhibitors oxalate and oxaloacetate provided protection against inactivation of the oxidase by PLP. These results suggest that PLP inactivates the enzyme by fonning a Schiff base with lysyl residue(s) at an active site of the oxidase. The enzyme was also inactivated by tryptophan-specific reagent N-bromosuccinimide (NBS). However, competitive inhibitors oxalate and oxaloacetate could not protect the oxidase significantly against inactivation of the enzyme by NBS. The results implicate that the inactivation of the oxidase by NBS is not directly related to modification of the tryptophanyl residue at an active site of the enzyme. Treatments of the oxidase with cysteine-specific reagents iodoacetate, silver nitrate, and 5,5'-dithiobis-2-nitrobenzoic acid did not affect significantly the activity of the enzyme.

• Journal of Microbiology and Biotechnology
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• v.1 no.2
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• pp.90-95
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• 1991

A ${\alpha}-galactosidase{\;}({\alpha}-D-galactoside$ galactohydrolase; EC 3.2.1.22) was purified from the culture filtrate of Penicillium purpurogenum by DEAE-cellulose column chromatography, gel filtration of Bio gel p-l00, and subsequent SP-Sephadex C-25 chromatography. The final preparation thus obtained showed a single band on polyacrylamide disc-gel and SDS-polyacrylamide gel electrophoresis. The molecular weight and isoelectric point were determined to be 63,000 and pH 4.0 by SDS-polyacrylamide gel electrophoresis and isoelectric focusing, respectively. The galactosidase exhibited maximum activity at pH 4.5 and $55^{\circ}C$, and was stable between pH 2 and 5, and also stable up to $40^{\circ}C$. The enzyme activity was not affected considerably by treatment with other metal compounds except mercuric chloride and silver nitrate. Copra galactomannan was finally hydrolyzed to galactose, mannose and mannobiose through the sequential actions of the purified galactosidase and mannanase from the same strain. The enzyme hydrolyzed melibiose and raffinose, but not lactose.

• Journal of Microbiology and Biotechnology
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• v.20 no.11
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• pp.1513-1520
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• 2010

A bacterium capable of producing melanin pigment in the presence of L-tyrosine was isolated from a crop field soil sample and identified as Klebsiella sp. GSK based on morphological, biochemical, and 16S rDNA sequencing. The polymerization of this pigment occurs outside the cell wall, which has a granular structure as melanin ghosts. Chemical characterization of the pigment particles showed then to be acid resistant, alkali soluble, and insoluble in most of the organic solvents and water. The pigment got bleached when subjected to the action of oxidants as well as reductants. This pigment was precipitated with $FeCl_3$, ammoniacal silver nitrate, and potassium ferricynide. The pigment showed high absorbance in the UV region and decreased absorbance when shifted towards the visible region. The melanin pigment was further charecterized by FT-IR and EPR spectroscopies. A key enzyme, 4-hydroxyphenylacetic acid hydroxylase, that catalyzes the formation of melanin pigment by hydroxylation of L-tyrosine was detected in this bacterium. Inhibition studies with specific inhibitors, kojic acid and KCN, proved that melanin is synthesized by the DOPA-melanin pathway.

• Journal of Plant Biotechnology
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• v.33 no.4
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• pp.249-255
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• 2006

Effects of ethylene inhibitors like silver nitrate $(AgNO_3)$, cobalt chloride $(CoCl_2)$ and Salicylic acid (SA) on multiple shoot induction and their impact on ethylene production using embryonal cotyledon cultures of Cucumis sativus L. were examined. The optimum concentration of $AgNO_3\;(40{\mu}M),\;CoCl_2\;(20{\mu}M)\;and\;SA\;(20{\mu}M)$, separately, induced maximum number of shoots on Murashige and Skoog's (MS) medium supplemented optimally with $4.44{\mu}M$ BA and $0.25{\mu}M$ NAA. Among the three ethylene inhibitors tested, $AgNO_3$ produced maximum number of shoots when compared to $CoCl_2$ and SA Ethylene production was monitored in all the treatments with $AgNO_3/CoCl_2/SA$ and it was observed that the treatment with $AgNO_3$ alone showed increase in ethylene production when compared to $CoCl_2$ and SA Even though ethylene concentration was the highest in $AgNO_3$ treated explants, maximum number of shoots was obtained.