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Park, A Reum,Kim, Jung Sub,Kim, Kwang Su,Zhang, Kan,Park, Juhyun,Park, Jong Hyeok,Lee, Joong Kee,Yoo, Pil J. American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.3
<P>Although Si is a promising high-capacity anode material for Li-ion batteries (LIB), it suffers from capacity fading due to excessively large volumetric changes upon Li insertion. Nanocarbon materials have been used to enhance the cyclic stability of LIB anodes, but they have an inherently low specific capacity. To address these issues, we present a novel ternary nanocomposite of Si, Mn, and reduced graphene oxide (rGO) for LIB anodes, in which the Si–Mn alloy offers high capacity characteristics and embedded rGO nanosheets confer structural stability. Si–Mn/rGO ternary nanocomposites were synthesized by mechanical complexation and subsequent thermal reduction of mixtures of Si nanoparticles, MnO<SUB>2</SUB> nanorods, and rGO nanosheets. Resulting ternary nanocomposite anodes displayed a specific capacity of 600 mAh/g with ∼90% capacity retention after 50 cycles at a current density of 100 mA/g. The enhanced performance is attributed to facilitated Li-ion reactions with the MnSi alloy phase and the formation of a structurally reinforced electroconductive matrix of rGO nanosheets. The ternary nanocomposite design paradigm presented in this study can be exploited for the development of high-capacity and long-life anode materials for versatile LIB applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-3/am404608d/production/images/medium/am-2013-04608d_0008.gif'></P>
Park, Yeo-Reum,Park, Hye-Bin,Kim, Mi-Jeong,Jung, Bae-Dong,Lee, Seunghyung,Park, Choon-Keun,Cheong, Hee-Tae The Korean Society of Developmental Biology 2019 발생과 생식 Vol.23 No.1
We examined the effects of endoplasmic reticulum (ER) stress inhibitor treatment during the micromanipulation of porcine somatic cell nuclear transfer (SCNT) on the in vitro development of SCNT embryos. ER stress inhibitors such as salubrinal (200 nM) and tauroursodeoxycholic acid (TUDCA; $100{\mu}M$) were added to the micromanipulation medium and holding medium. The expression of X-box binding protein 1 (Xbp1), ER-stress-associated genes, and apoptotic genes in SCNT embryos was confirmed at the one-cell and blastocyst stages. Levels of Xbp1 splicing and expression of ER-stress-associated genes in SCNT embryos at the one-cell stage decreased significantly with TUDCA treatment (p<0.05). The expression of ER-stress-associated genes also decreased slightly with the addition of both salubrinal and TUDCA (Sal+TUD). The expression levels of caspase-3 and Bcl2-associated X protein (Bax) mRNA were also significantly lower in the TUDCA and Sal+TUD treatments (p<0.05). At the blastocyst stage, there were no differences in levels of Xbp1 splicing, and transcription of ER-stress-associated genes and apoptosis genes between control and treatment groups. However, the blastocyst formation rate (20.2%) and mean blastocyst cell number ($63.0{\pm}7.2$) were significantly higher (p<0.05) for embryos in the TUDCA treatment compared with those for control (12.6% and $41.7{\pm}3.1$, respectively). These results indicate that the addition of ER-stress inhibitors, especially TUDCA, during micromanipulation can inhibit cellular damage and enhance in vitro development of SCNT embryos by reducing stress levels in the ER.
Yeo-Reum Park,Hye-Bin Park,Hwa-Yeon Lee,Hyo-Kyung Bae,Hui-Yeon Shin,Seunghyung Lee,Choon-Keun Park,Boo-Keun Yang,Hee-Tae Cheong 한국수정란이식학회 2016 한국수정란이식학회 학술대회 Vol.2016 No.10
This study was conducted to examine the effects of activation methods on the ER stress induction and subsequent apoptosis and in vitro development of porcine parthenogenetic embryos. Porcine in vitro matured oocytes were activated by four activation methods; 1) electric stimulus(ES) with two DC pulses of 1.25 kV/cm, for 30 ㎲ (E), 2) ES + 10 μM Ca-ionophore (A23187) treatment for 5 min (EC), 3) ES + 2 mM 6-dimethylaminopurine treatment for 3 h (ED), or 4) ES + A23187 + 6-DMAP (ECD). After activation, parthenogenetic embryos were in vitro cultured in PZM-3 medium and sampled to analyze the x-box binding protein 1 (Xbp1) mRNA, ER stress-associated genes and apoptotic genes at 3 h post ES and the 1-cell and blastocyst stages. The un-spliced and spliced x-box binding protein 1 (Xbp1) mRNA were confirmed by RT-PCR. Also ER stress-associated genes, such as the C/EBP homologous protein (CHOP), binding protein (BiP), activating transcription factor 4 (ATF4) and glucose-regulated protein 94 (GRP94), and apoptotic genes were analyzed by real-time quantitative RT-PCR (RT-qPCR). The band intensities of spliced Xbp1 (Xbp1s) mRNA was higher in the EC group than other three groups at 3 h and the 1-cell stage, while it was higher in the ED groups compared with E group at the blastocyst stage. Four ER stress-associated genes were showed the highest expression in the EC group and weakly expressed in the ED group at 3 h. However, most of those genes were highly expressed in EC and ECD groups at the 1-cell and blastocyst stages with some variation. The expressions of Bcl-2-associated X protein (Bax) and caspase-3 mRNAs were significantly higher in EC group than other three groups at all stages. The developmental rate to the blastocyst stage was higher (p<0.05) in ED and ECD groups (32.1±3.8 to 34.6±2.2%) than that of E group (26.1±3.9%). These results suggest that the intracellular ER stress of parthenogenetic porcine embryos is affected by activation method and subsequently lead to the apoptosis of embryos.
Microbial Transformation of Trichostatin A to 2,3-Dihydrotrichostatin A
Park, Je Won,Park, Sung Ryeol,Han, Ah Reum,Ban, Yeon-Hee,Yoo, Young Ji,Kim, Eun Ji,Kim, Eunji,Yoon, Yeo Joon American Chemical Society and American Society of 2011 Journal of natural products Vol.74 No.5
<P>A new reduced hydroxamate, 2,3-dihydrotrichostatin A, was created from trichostatin A by employing a recombinant strain of <I>Streptomyces venezuelae</I> as a microbial catalyst. Compared with trichostatin A, 2,3-dihydrotrichostatin A showed similar antifungal activity against <I>Saccharomyces cerevisiae</I>, but, interestingly, approximately twice the cytostatic activity against human small-cell lung cancer cells. The production of 2,3-dihydrotrichostatin A via microbial biotransformation demonstrates that the regiospecific and substrate-flexible hydrogenation by <I>S. venezuelae</I> provides a new approach for creating natural product analogues with improved bioactive properties.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jnprdf/2011/jnprdf.2011.74.issue-5/np1006718/production/images/medium/np-2010-006718_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/np1006718'>ACS Electronic Supporting Info</A></P>
Regulation of dendritic arborization by BCR Rac1 GTPase-activating protein, a substrate of PTPRT.
Park, A-Reum,Oh, Daeyoung,Lim, So-Hee,Choi, Jeonghoon,Moon, Jeonghee,Yu, Dae-Yeol,Park, Sung Goo,Heisterkamp, Nora,Kim, Eunjoon,Myung, Pyung-Keun,Lee, Jae-Ran Cambridge University Press 2012 Journal of cell science Vol.125 No.19
<P>Dendritic arborization is important for neuronal development as well as the formation of neural circuits. Rac1 is a member of the Rho GTPase family that serve as regulators of neuronal development. Breakpoint cluster region protein (BCR) is a Rac1 GTPase-activating protein that is abundantly expressed in the central nervous system. Here, we show that BCR plays a key role in neuronal development. Dendritic arborization and actin polymerization were attenuated by overexpression of BCR in hippocampal neurons. Knockdown of BCR using specific shRNAs increased the dendritic arborization as well as actin polymerization. The number of dendrites in null mutant BCR(-/-) mice was considerably increased compared with that in wild-type mice. We found that the function of the BCR GTPase-activating domain could be modulated by protein tyrosine phosphatase receptor T (PTPRT), which is expressed principally in the brain. We demonstrate that tyrosine 177 of BCR was the main target of PTPRT and the BCR mutant mimicking dephosphorylation of tyrosine 177 alleviated the attenuation of dendritic arborization. Additionally the attenuated dendritic arborization found upon BCR overexpression was relieved upon co-expression of PTPRT. When PTPRT was knocked down by a specific shRNA, the dendritic arborization was significantly reduced. The activity of the BCR GTPase-activating domain was modulated by means of conversions between the intra- and inter-molecular interactions, which are finely regulated through the dephosphorylation of a specific tyrosine residue by PTPRT. We thus show conclusively that BCR is a novel substrate of PTPRT and that BCR is involved in the regulation of neuronal development via control of the BCR GTPase-activating domain function by PTPRT.</P>
Park, A Reum,Nam, Myeong Gyun,Kim, A-Young,Kim, Kwang Su,Sher Shah, Md. Selim Arif,Lee, Jun Young,Kim, Woo-Jae,Lee, Joong Kee,Yoo, Pil J. Elsevier 2017 Journal of Alloys and Compounds Vol.724 No.-
<P><B>Abstract</B></P> <P>Silicon (Si) is a promising anode material for high-performance Li-ion batteries (LIBs), but it undergoes rapid capacity fading through severe volumetric expansion during Li insertion/extraction. Although alloying Si with various metal sources has been pursued to mitigate the structural deterioration, the resulting materials have shown the intrinsic problem of low electrical conductivity. To address this conflicting issue, here we describe a novel ternary nanocomposite of Si/Co-CoSi<SUB>2</SUB>/reduced graphene oxide (rGO) made using a facile process of mechanical mixing of Si nanoparticles, Co<SUB>3</SUB>O<SUB>4</SUB> microparticles, and rGO nanosheets, followed by carbothermal reduction. Specifically, rGO, which has high electrical conductivity and structural integrity, could work as both a conductive matrix and a reducing agent in forming the Co-CoSi<SUB>2</SUB> phase inside the Si domains during thermal treatment. The proposed ternary nanocomposites exhibited a noteworthy specific capacity of 952 mA h g<SUP>−1</SUP> with 79.3% capacity retention after 80 cycles at a current density of 100 mA g<SUP>−1</SUP>. We attribute the improved electrochemical performance to the increased structural stability offered by the Co-CoSi<SUB>2</SUB> phase and the interconnected conductive framework of the rGO nanosheets. Therefore, we expect our design process for Si/Co-CoSi<SUB>2</SUB>/rGO ternary nanocomposites to be applicable to other materials that can eventually be used as high-performance anodes for the next generation LIBs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A new Si/Co-CoSi<SUB>2</SUB>/rGO ternary nanocomposite is suggested as Li-ion battery anodes. </LI> <LI> An electroconductive yet Li-inactive phase of Co-CoSi<SUB>2</SUB> is incorporated into a Si matrix. </LI> <LI> Encompassing rGO nanosheets provide mechanical stability and conductivity during cycles. </LI> <LI> Ternary nanocomposite exhibits excellent electrochemical performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Discovery of parallel pathways of kanamycin biosynthesis allows antibiotic manipulation
Park, Je Won,Park, Sung Ryeol,Nepal, Keshav Kumar,Han, Ah Reum,Ban, Yeon Hee,Yoo, Young Ji,Kim, Eun Ji,Kim, Eui Min,Kim, Dooil,Sohng, Jae Kyung,Yoon, Yeo Joon Nature Publishing Group, a division of Macmillan P 2011 Nature chemical biology Vol.7 No.11
Kanamycin is one of the most widely used antibiotics, yet its biosynthetic pathway remains unclear. Current proposals suggest that the kanamycin biosynthetic products are linearly related via single enzymatic transformations. To explore this system, we have reconstructed the entire biosynthetic pathway through the heterologous expression of combinations of putative biosynthetic genes from Streptomyces kanamyceticus in the non??aminoglycoside-producing Streptomyces venezuelae. Unexpectedly, we discovered that the biosynthetic pathway contains an early branch point, governed by the substrate promiscuity of a glycosyltransferase, that leads to the formation of two parallel pathways in which early intermediates are further modified. Glycosyltransferase exchange can alter flux through these two parallel pathways, and the addition of other biosynthetic enzymes can be used to synthesize known and new highly active antibiotics. These results complete our understanding of kanamycin biosynthesis and demonstrate the potential of pathway engineering for direct in vivo production of clinically useful antibiotics and more robust aminoglycosides.
Park, Ah-Reum,Kim, Hye-Jung,Lee, Jung-Kul,Oh, Deok-Kun Springer-Verlag 2010 Applied biochemistry and biotechnology Vol.160 No.8
<P>We expressed a putative beta-galactosidase from Sulfolobus acidocaldarius in Escherichia coli and purified the recombinant enzyme using heat treatment and Hi-Trap ion-exchange chromatography. The resultant protein gave a single 57-kDa band by SDS-PAGE and had a specific activity of 58 U/mg. The native enzyme existed as a dimer with a molecular mass of 114 kDa by gel filtration. The maximum activity of this enzyme was observed at pH 5.5 and 90 degrees C. The half-lives of the enzyme at 70, 80, and 90 degrees C were 494, 60, and 0.2 h, respectively. The hydrolytic activity with p-nitrophenyl(pNP) substrates followed the order p-nitrophenyl-beta-D-fucopyranoside>pNP-beta-D-glucopyranoside>pNP-beta-D- galactopyranoside>pNP-beta-D-mannopyranoside>pNP-beta-D-xylopyranoside, but not toward aryl-alpha-glycosides or pNP-beta-L-arabinofuranoside. Thus, the enzyme was actually a beta-glycosidase. The beta-glycosidase exhibited transglycosylation activity with pNP-beta-D-galactopyranoside, pNP-beta-D-glucopyranoside, and pNP-beta-D-fucopyranoside in decreasing order of activity, in the reverse order of its hydrolytic activity. The hydrolytic activity was higher toward cellobiose than toward lactose, but the transglycosylation activity was lower with cellobiose than with lactose.</P>