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Mun, Hueong-Tae,Namgung, Jeong,Namgung, Jeong-Hee-Namgung The Ecological Society of Korea 2000 Journal of Ecology and Environment Vol.23 No.2
Mass loss and changes of mineral nutrients during decomposition of Phragmites communis for 13 months from November 1998 to December 1999, were investigated at the fringe of stream at Boryeong, Chungnam Province in Korea. Plant materials, which were collected in November 1998. were divided into leaves, culms and rhizomes. Litterbags, 15${\times}$15 cm, were made of nylon mesh with 2-mm$^2$ holes. At 13 months after installation, remaining mass of leaves, culms and rhizomes was 29.0%, 57.4%, 20.6%, respectively. Mass loss rate of the culms was significantly lower than those of the leaves and rhizomes. The decay rate of leaves, culms and rhizomes was 1.21. 0.42 and 1.48 per year, respectively. Initial concentration of N, P, K, Ca and Mg of leaves. culms and rhizomes was 22.5, 9.0, 15.5 mg/g for N, 0.34. 0.10, 0.33 mg/g for P, 15.0, 12.5. 12.3 mg/g for K, 2.84. 0.80, 0.03 mg/g for Ca. 1.94. 0.97, 0.40 mg/g for Mg, respectively. Concentrations of nutrients were higher in leaves than in culms and rhizomes. Except for N and Mg in rhizomes, there was no immobilization period during the decomposition. In the case of remaining K and Ca, most are lost during the first 3 months. Without any suitable method for removal of dead part, eutrophication of freshwater may be accelerated by dead macrophytes.
Ecofriendly one-pot biosynthesis of indigo derivative dyes using CYP102G4 and PrnA halogenase
Namgung, Seyun,Park, Hyun A.,Kim, Joonwon,Lee, Pyung-Gang,Kim, Byung-Gee,Yang, Yung-Hun,Choi, Kwon-Young Elsevier 2019 Dyes and pigments Vol.162 No.-
<P><B>Abstract</B></P> <P>In this study, the biosynthesis of various indigoids with novel spectral features and antibacterial activities was investigated. First, 12 indole derivatives as substrates were biotransformed into functional indigoid dyes by <I>E. coli</I> cells expressing CYP102G4 hydroxylase. The indole derivatives included chloro (Cl-), nitro (NO<SUB>2</SUB>-), hydroxy (HO-), methoxy (CH<SUB>3</SUB>O-), methyl (CH<SUB>3</SUB>-), carboxy (COOH-), amino (NH<SUB>3</SUB>-), and cyano (CN-) indoles at the C4 to C7 positions. Interestingly, dramatic color shifts were observed from blue to red, green, purple, and even pink depending on the functional groups and their positions. Next, the biological and physical properties, antibacterial effects, and dying fastness of the prepared compounds were investigated and visually measured. Among the synthesized indigoid dyes, 6,6’-dichloroindigo and 5,5’-dichloroindigo showed the relatively higher cell growth inhibitory activity in the liquid phase. Finally, a one-pot producing strain which produced 7,7’-dichloroindigo from <SMALL>L</SMALL>-tryptophan using tryptophan-7-halogenase (PrnA) and CYP102G4 simultaneously was developed to overcome the disadvantages of uneconomical semi-synthesis through indole precursor feedstocks. The developed producing strain produced approximately 15.4 ± 1.4 mg/L of 7,7’-dichloroindigo in 24 h. To the best of our knowledge, this is the first report of the production of 7,7’-dichloroindigo in <I>E. coli</I> via a one-pot process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biological production of eco-friendly indigo derivatives. </LI> <LI> Biotransformation of indole derivatives using CYP102G4. </LI> <LI> One-pot biosynthesis of 7,7’-dichloroindigo by CYP102G4 and PrnA. </LI> <LI> 15.4 mg/L of 7,7’-dichloroindigo production in <I>E. coli</I>. </LI> <LI> Antibacterial activity of indigo derivatives. </LI> </UL> </P>
Namgung, N.,Shin, D.H.,Park, S.W.,Paik, I.K. Asian Australasian Association of Animal Productio 2010 Animal Bioscience Vol.23 No.7
The objective of this research was to evaluate the effects of dietary supplementation of blood meal (BM) as a source of histidine, and magnesium oxide (MgO) as a catalyst of carnosine synthetase, on carnosine (L-Car) content in the chicken breast muscle (CBM), laying performance, and egg quality of spent old hens. Four hundred eighty laying hens (Hy-Line$^{(R)}$ Brown), 95wk old, were allotted randomly into five replicates of six dietary treatments: T1; 100% basal diet, T2; 100% basal diet+MgO, T3; 97.5% basal diet+2.5% BM, T4; 97.5% basal diet+2.5% BM+MgO, T5; 95% basal diet+5% BM, T6; 95% basal diet+5% BM+MgO. Magnesium oxide was added at 0.3% of diets. The layers were fed experimental diets for 5wk. There were no significant differences in the weekly L-Car content in CBM among all treatments during the total experimental period, but some of the contrast comparisions showed higher L-Car in CBM of T6. The L-Car contents linearly decreased (p<0.01 or p<0.05) as the layers got older except in T4 (p>0.05). There were significant differences in egg weight (p<0.01) and soft and broken egg ratio (p<0.05). The control (T1) was highest in egg weight and T6 was lowest in soft and broken egg ratio. Among the parameters of egg quality, there were significant differences in eggshell strength (p<0.01) and egg yolk color (p<0.05). Magnesium oxide supplementation increased the eggshell strength and BM tended to decrease egg yolk color. Eggshell color, eggshell thickness, and Haugh unit were not influenced by BM and MgO. In conclusion, BM and MgO did not significantly influence the L-Car in CBM of spent layers. The L-Car content rapidly decreased as the layers became senescent. Eggshell strength was increased by MgO supplementation.
Namgung, Ho,Kim, Choongho,Kim, Yujun,Kim, Jongho,Lee, Taek Seung American Scientific Publishers 2016 Journal of nanoscience and nanotechnology Vol.16 No.8
<P>We report the synthesis of a fluorescent polymer containing the rhodamine 6G (Rh6G) derivative as a side chain. The rhodamine (Rh) moiety in the polymer had a ligand interaction with Al3+, which allowed the polymer to be used for detection of Al3+. The Rh moiety (in closed form) was non-fluorescent and colorless, whereas the open form of the Rh derivative showed strong fluorescence. Upon exposure to Al3+, the green-emitting polymer backbone had a spectral overlap with the absorption of the open form of Rh in the side chain, leading to an energy transfer from the polymer backbone to the Rh moiety. Upon addition of Al3+ to the polymer solution, the emission of the polymer backbone (green) has gradually decreased and, concomitantly, the red emission of Rh has increased via Forster resonance energy transfer (FRET). As the fluorescence of the polymer varied in the presence of Al3+ ions, the polymer could be used as a FRET-based sensor for detecting Al3+.</P>
Namgung, Gitae,Ta, Qui Thanh Hoai,Noh, Jin-Seo Elsevier 2018 Chemical physics letters Vol.703 No.-
<P><B>Abstract</B></P> <P>Stretchable hydrogen sensors were fabricated from Pd nanosheets that were transferred onto a PDMS substrate. To prepare the Pd nanosheets, a Pd thin film on PDMS was first biaxially stretched and then PDMS substrate was etched off. The size of Pd nanosheets decreased as the applied strain increased and the film thickness decreased. A transfer technique was utilized to implement the stretchable hydrogen sensors. The stretchable sensors exhibited negative response behaviors upon the exposure to hydrogen gas. Interestingly, the sensors worked even under large strains up to 30%, demonstrating a potential as a high-strain-tolerable hydrogen sensor for the first time.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Palladium (Pd) nanosheets were prepared by a combination of biaxial stretching and PDMS delamination. </LI> <LI> The size of Pd nanosheets could be controlled by adjusting the applied strain and film thickness. </LI> <LI> Stretchable hydrogen gas sensors were fabricated using the Pd nanosheets. </LI> <LI> The stretchable sensors responded to hydrogen gas even under a 30% strain. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Pd nanosheets were prepared by biaxially stretching a Pd film on PDMS and subsequently delaminating the PDMS. It was demonstrated that stretchable hydrogen sensors fabricated from the Pd nanosheets could respond to hydrogen gas even under large strains up to 30%.</P> <P>[DISPLAY OMISSION]</P>
Cr(OH)<sub>3</sub>(s) Oxidation Induced by Surface Catalyzed Mn(II) Oxidation
Namgung, Seonyi,Kwon, Man Jae,Qafoku, Nikolla P.,Lee, Giehyeon American Chemical Society 2014 Environmental science & technology Vol.48 No.18
<P>We examined the feasibility of Cr(OH)<SUB>3</SUB>(s) oxidation mediated by surface catalyzed Mn(II) oxidation under common groundwater pH conditions as a potential pathway of natural Cr(VI) contaminations. Dissolved Mn(II) (50 μM) was reacted with or without synthesized Cr(OH)<SUB>3</SUB>(s) (1.0 g/L) at pH 7.0–9.0 under oxic or anoxic conditions. Homogeneous Mn(II) oxidation by dissolved O<SUB>2</SUB> was not observed at pH ≤ 8.0 for 50 days. At pH 9.0, by contrast, dissolved Mn(II) was completely removed within 8 days and precipitated as hausmannite. When Cr(OH)<SUB>3</SUB>(s) was present, this solid was oxidized and released substantial amounts of Cr(VI) as dissolved Mn(II) was added into the suspension at pH ≥ 8.0 under oxic conditions. Production of Cr(VI) was attributed to Cr(OH)<SUB>3</SUB>(s) oxidation by a newly formed Mn oxide via Mn(II) oxidation catalyzed on Cr(OH)<SUB>3</SUB>(s) surface. XANES results indicated that this surface-catalyzed Mn(II) oxidation produced a mixed valence Mn(III/IV) solid phase. Our results suggest that toxic Cr(VI) can be naturally produced via Cr(OH)<SUB>3</SUB>(s) oxidation coupled with the oxidation of dissolved Mn(II). In addition, this study evokes the potential environmental hazard of sparingly soluble Cr(OH)<SUB>3</SUB>(s), which has been considered the most common and a stable remediation product of Cr(VI) contamination.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/esthag/2014/esthag.2014.48.issue-18/es503018u/production/images/medium/es-2014-03018u_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/es503018u'>ACS Electronic Supporting Info</A></P>